-'111111111 - Waste Isolation Pilot Plant

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-'111111111 - Waste Isolation Pilot Plant

ACKNOWLEDGEMENTSThe authors wish to thank Lee Jensen, Wayne Stensrud, Jeff Palmer, Randy Roberts, Paul Domski, KentLantz, and Michael Bame for their efforts in fielding the tests discussed in this report. We would also like tothank Chris Neuzil, Susan Howarth, John Stormont, Dave McTigue, Dave Borns, Wolfgang Wawersik,Darrell Munson, and John Pickens for their helpful review comments. TIm Dale performed a valuable consistencyreview of the manuscript and assisted with figure preparation. Bob Jones' and Darcy Pulliam'sefforts in preparing the camera-ready version of the manuscript are also appreciated.ii


TABLE OF CONTENTS1. INTRODUCTION .2. GEOLOGIC SETTING AND LOCAL STRATIGRAPHy 33. TESTING EQUiPMENT _ 73.1 Multipacker Test Tool _ 73.2 Data-Acquisition System 73.3 Pressure Transducers 113.4 Thermocouples.................................................................... 113.5 Linear Variable-Differential Transfonners 113.6 Compliance-Testing Equipment 134. TESTING PROCEDURES '.' _ 174.1 Compliance Testing _. _ 174.2 Pressure-Pulse Testing " 215. TEST LOCATIONS AND BOREHOLES _.. _ , 235.1 Room C2 255.2 North 1420 Drift , 255.3 Room L4 _ , 285.4 South 1300 Drift 285.5 Waste Panel 1, Room 7 286. INTERPRETATION METHODOLOGy 336.1 Well-Test-Simulation Model 336.2 Assumptions Used in Test Analysis 346.3 Material Properties Used in Test Simulations 366.3.1 Formation Porosity 366.3.2 Formation Elastic Moduli 366.3.3 Brine Compressibility __ 366.3.4 Formation Brine Density 386.3.5 Estimation of Specific Storage 386.3.6 Thermal-Expansion Coefficient of Test-Zone Brine 406.4 Test-Zone Volume 406.4.1 Initial Test-Zone Volume 416.4.2 Compensation for Changes in Test-Zone Volume 426.5 Test-Zone Compressibility _ _ 446.6 Thermal Effects _ 467. ESTIMATION OF HYDRAULIC PROPERTIES _ 477.1 Individual Test Interpretations __ 477.1.1 C2H01-A 477.1.1.1 Testlone 47iii


8.2 Future Testing Plans and Considerations , , , . 1308.3 Conclusions 131REFERENCES _ 132APPENDIX A: Summary of Surface-Based Hydraulic Testing of the Salado Formation 137APPENDIX B: Stratigraphic Units (Map Units) Near the WIPP Facility Horizon 141APPENDIX C: Core Logs _ , 149APPENDIX D: Factors Affecting Test-Zone Compressibility 177DISTRIBUTION _ 197v


FIGURES1-1 LocationoftheWIPPSite 12-1 WIPP Site Stratigraphic Column 32-2 Detailed Stratigraphy Near the WIPP Underground Facility 42-3 Schematic of Typical WIPP Underground Rooms Showing Stratigraphic Positions 53-1 Multipacker Test Tool #1 Used in C2H01-A and C2H01-B Testing and inWaste-Handling Sh9ftTesting 83-2 Typical Configuratiotl of the MUltipacker Test Tools Designed for Underground Testing 93-3 Detail of Test- and Guard-Zone Sections of the Multipacker Test Tool 103-4 Schematic Illustration of the Data-Acquisition System 123-5 Movement of Sliding-End Sub in Guard Zone During Packer Inflation 143-6 Cross-Section View of Stainless-Steel Compliance-Testing Chamber in Borehole P4P30 154-1 Zone Pressures for Compliance Test CaMP 16, Multipacker Test Tool #5, Borehole C2H03 ... 194-2 Packer Pressures for Compliance Test CaMP 16, Multipacker Test Tool #5, Borehole C2H03 .. 194-3 Zone Temperatures for Compliance Test CaMP 16, Multipacker Test Tool #5,Borehole C2H03 - 204-4 Radial-LVDT Data for Compliance Test CaMP 16, Multipacker Test Tool #5, Borehole C2H03 .. 204-5 Axial-LVDT Data for Compliance Test CaMP 16, Multipacker Test Tool #5, Borehole C2H03 214-6 Typical Permeability-Testing Sequence 225-1 Map of the WIPP Underground Facility Showing Test Locations 245-2 Positions of Boreholes C2H01, C2H02, and C2H03 in Room C2 265-3 Position of Borehole N4P50 in the North 1420 Drift 275-4 Position of Borehole L4P51 in Room L4 295-5 Position of Borehole SOP01 in the South 1300 Drift 305-6 Position of Borehole 51 P71 in Waste Panel 1, Room 7 317-1 Configuration of Multipacker Test Tool #1 in Borehole C2H01 for C2H01-A Testing 497-2 Test- and Guard-Zone Fluid-Pressure Data from C2H01-A Testing 507-3 Best-Fit Model Simulation of the Test-Zone Fluid-Pressure Response DuringC2H01-A Testing 517-4 Simulated Formation Pore Pressures at Selected Radial Distances from the TestZone During C2H01-A Testing 527-5 Best-Fit Model Simulation of the Test-Zone Fluid-Pressure Response DuringC2H01-A Testing, Assuming a Simulation Thickness of 0.83 m 537-6 Simulated Formation Pore Pressures at Selected Radial Distances from theTest Zone During C2H01-A Testing, Assuming a Simulation Thickness of 0.83 m 537-7 Configuration of Multipacker Test Tool #1 in Borehole C2H01 for C2H01-B Testing 557-8 Test- and Guard-Zone Fluid-Pressure Data from C2H01-B Testing 567-9 Best-Fit Model Simulation of the Test-Zone Fluid-Pressure Response DuringC2H01-B Testing 57vi


7-40 Best-Fit Model Simulation of the Test-Zone Fluid-Pressure Response DuringS1 P71-A Testing _ 897-41 Simulation of the Test-Zone Fluid-Pressure Response During C2H01-ATesting Showing the Simulation's Sensitivity to Hydraulic Conductivity 917-42 Simulation of the Test-Zone Fluid-Pressure Response During C2H01-BTesting Showing the Simulation's Sensitivity to Hydraulic Conductivity 917-43 Simulation of the Guard-Zone Fluid-Pressure Response During C2H01-BTesting Showing the Simulation's Sensitivity to Hydraulic Conductivity 927-44 Simulation of the Test-Zone Fluid-Pressure Response During C2H01-CTesting Showing the Simulation's Sensitivity to Hydraulic Conductivity 927-45 Simulation of the Test-Zone Fluid-Pressure Response During C2H02Testing Showing the Simulation's Sensitivity to Hydraulic Conductivity 937-46 Simulation of the Test-Zone Fluid-Pressure Response During L4P51-ATesting Showing the Simulation's Sensitivity to Hydraulic Conductivity 937-47 Simulation of the Test-Zone Fluid-Pressure Response During SOP01Testing Showing the Simulation's Sensitivity to Hydraulic Conductivity 947-48 Simulation of the Test-Zone Fluid-Pressure Response During S1 P71-ATesting Showing the Simulation's Sensitivity to Hydraulic Conductivity 947-49 Simulation of the Test-Zone Fluid-Pressure Response During C2H01-ATesting Showing the Simulation's Sensitivity to Formation Pore Pressure 957-50 Simulation of the Test-Zone Fluid-Pressure Response During C2H01-BTesting Showing the Simulation's Sensitivity to Formation Pore Pressure 957-51 Simulation of the Guard-Zone Fluid-Pressure Response During C2H01-BTesting Showing the Simulation's Sensitivity to Formation Pore Pressure 967-52 Simulation of the Test-Zone Fluid-Pressure Response During C2H01-CTesting Showing the Simulation's Sensitivity to Formation Pore Pressure 967-53 Simulation of the Test-Zone Fluid-Pressure Response During C2H02Testing Showing the Simulation's Sensitivity to Formation Pore Pressure 977-54 Simulation of the Test-Zone Fluid-Pressure Response During L4P51-ATesting Showing the Simulation's Sensitivity to Formation Pore Pressure 977-55 Simulation of the Test-Zone Fluid-Pressure Response During SOP01Testing Showing the Simulation's Sensitivity to Formation Pore Pressure 987-56 Simulation of the Test-Zone Fluid-Pressure Response During S1 P71-ATesting Showing the Simulation's Sensitivity to Formation Pore Pressure 987-57 Simulation of the Test-Zone Fluid-Pressure Response During L4P51-ATesting Showing the Simulation's Sensitivity to Distance to the Zero-Flow Boundary 997-58 Simulation of the Test-Zone Fluid-Pressure Response During S1 P71-ATesting Showing the Simulation's Sensitivity to Distance to the Zero-Flow Boundary 997-59 Simulation of the Test-Zone Fluid-Pressure Response During C2H01-ATesting Showing the Simulation's Sensitivity to Specific Storage. . . . . . . . . . . . . . . . . . . . . . .. 1017-60 Simulation of the Test-Zone Fluid-Pressure Response During C2H01-BTesting Showing the Simulation's Sensitivity to Specific Storage 1017-61 Simulation of the Guard-Zone Fluid-Pressure Response during C2H01-BTesting Showing the Simulation's Sensitivity to Specific Storage " 1027-62 Simulation of the Test-Zone Fluid-Pressure Response during C2H01-CTesting Showing the Simulation's Sensitivity to Specific Storage. . . . . . . . . . . . . . . . . . . . . . .. 102viii


TABLES6-1 Reference Elastic Moduli of Salado Lithologies 376-2 Specific Storage Values Used in Test Interpretations 406-3 Test-Zone Compressibilities Calculated from Fluid Volumes Measured DuringPulse Withdrawals 437-1 Test-Interpretation Results 48xi


1. INTRODUCTIONThis report presents preliminary interpretations of hydraulictests conducted in bedded evaporites of theSalado Formation from 1988 through early 1990 at theWaste Isolation Pibt Plant (WIPP) site in southeasternNew Mexico (Figure 1-1). The WIPP is a U.S. Departmentof Energy research and development facilitydesigned to demonstrate safe disposal of transuranicwastes resulting from the nation's defense programs.The WIPP disposal horizon is located in the lowerportion ofthe Permian Salado Formation. The hydraulictests discussed in this report were pertormed in theWIPP underground facility by INTERA Inc., Austin,Texas, underthetechnical direction of Sandia NationalLaboratories, Albuquerque, New Mexico.Hydraulic testing is being performed in the SaladoFormation to provide quantitative estimates of thehydraulic properties controlling brine flow through theSalado Formation. The specific objectives of the testsare:• Todeterminepermeabilities of different stratigraphicintervals in the Salado Formation around the WIPPfacility;• To determine formation pore pressures within differentstratigraphic intervals in the Salado Formationaround the facility;• To determine whether or not hydraulic boundariesare encountered within the Salado on the scale oftesting;• To define the distance(s) to which the presence ofthe WIPP facility has affected hydraulic propertiesandlorformation pore pressures in the surroundingrock; andNew MexIco• To provide data which may _allow discriminationbetween different conceptual models that attemptto explain flow through evaporites, such as a Darcyflowmodel in which flow is driven by pore-pressuregradients, and a stress- or creep-driven flow modelin which bri"e is sq:.;zezed out of the formation byplastic deformation of the rock.From 1976 to 1985, a number of hydraulic tests of theNew MexicoSalado Formation were performed in boreholes drilledfrom the surface. Drillstem tests (DSTs), air-injectionWIPPSITEtests, and/or pressure-pulse tests were pertormed inboreholes ERDA-9, ERDA-10, AEC-7, AEC-8, CabinNt,,'''--__~...2-=____--=.J.=.......Jo 5 10 15 mi""""'"=---Jooo..j~~o 10 20 kmTR!-6J30-3-2Baby-1, DOE-2, and WIPP-12, but none provided datathat could be interpreted to yield reliable estimates offormation permeability and/or pore pressure (AppendixA). In 1986, permeability tests of portions of theSalado were performed in several holes drilled fromwithin the WIPP underground facility using both air andbrine as test fluids. Peterson et al. (1987) interpretedFigure 1-1.Location of the WIPP Site.


hydraulic conductivities ranging from 7 x 10- 15 to 3 x10- 12 mts from these tests. In 1987. permeabilitytesting was performed at two depths in the Salado inholes drilled from within the waste-handling shaft at theWIPP site (Stensrud et aI., 1988). Interpretation ofthedata from these tests indicated hydraulic conductivitiesranging from 2 x 10- 14 to 1 x 10- 13 mls (Saulnier andAvis, 1988). Following these experiences, testing inholes drilled from within the WI PP underground facilitywas considered to have a greater likelihood of successthan continued attempts at surface-based testing,leading to the development of the testing programdiscussed in this report.for these changes is complicated by the dependenceof creep rates around a borehole on the fluid pressurein the borehole. In addition. because halite and otherevaporites tend to have extremely low permeabilities.temperature changes and equipment-related factorsthat have negligible effects on tests in higherpermeability media may significantly affect observedfluid-pressure responses in evaporites. Thus, theeffects of temperature changes, pressure-dependenttest-tool-volume changes (compliance). and movementofthetesttool dUring testing also need to beincorporatedinto the test interpretation.The hydraulic testing reported herein consists ofpressure-pulse testsoHive stratigraphic intervalswithineleven meters of the WIPP excavations_ Thestratigraphic intervals tested include halite (both pureand impure), anhydrite. and clay. From September1988 through February 1990. nine sets of pulse testswere completed in five different boreholes. Testing ofa sixth stratigraphic interval consisting entirely ofrelatively pure halite was attempted in anotherborehole.but no interpretable response was observed. Testingof a seventh stratigraphic interval was begun, but hadto be terminated prematurely because of conflicts withother activities in that part of the WIPP undergroundfacility.Unlike porous media such as sandstones. halite exhibitscreep behavior that may complicate the interpretationof hydraulic tests. Creepcauses borehole dimensionsto change during tests and may also cause timedependentchanges in the permeability and specificstorageofthe region undergoingcreep. CompensatingOther factors specific to the tests of the SaladoFormation, which bear on test interpretation, areborehole orientation (in some cases the holes were notdrilled perpendicular to bedding), possible partialpenetrationeffects (test intervals may not have beenfully confined). the effect of trapped gas within testintervals on test-zone compressibility, and possibletwo-phase flow caused by gas having exsolved fromthe Salado brine in the relatively depressurized nearboreholeregion of the surrounding rock.The interpretations presented in this report are termedupreliminary" because they do not fully incorporate allof the complexities discussed above. In particular,formation creep, partial-penetration effects, pressuredependenttest-zone compressibility resulting from thepresence of gas, and two-phase flow are notquantitatively addressed in this report. Additionalexperimentation, study, and model development willbe required before many of these complexities can beincorporated into the test interpretations.2


2. GEOLOGIC SETTING AND LOCAL STRATIGRAPHYThe WI PP site is located in the northern part of theDelaware Basin in southeastern New Mexico. WIPPsitegeologic investigations have concentrated on theupper seven formations typically found in that part ofthe Delaware Basin. These are, in ascending order,the Bell Canyon Formation, the Castile Formation, theSalado Formation, the Rustler Formation, the DeweyLake Red Beds, the Dockum Group, and the GatuMFormation (Figure 2-1). All ofthese formations are ofPermian age, except for the Dockum Group, which isof Triassic age, and the GatuFla, which is a Quaternarydeposit.The WIPP underground facility lies in the lower part ofthe Salado Formation at an approximate depth of655 m below ground surface. The Salado FormationSYSTEM SERIES GROUP FORMATION MEMBERRECENT RECENT SURFICIAL DEPOSITSQUATER- PLEISTO- MESCALERO CALICHENARY CENEGATUNATRIASSiC DOCKUM UNDIVIDEDz


-17•.47I.....- ::: -.. -AIIOI.UC£OUS HAUTEx- x >


ClaysMapUrnB.. ) ':4 .15 Clear to grayish orange-pink hBl~e. IrBal 01 dispersed potyhal~e arc! inlercrystalline clay.I..,....--.,;;----......------i13'2Clear to grayish orange-pink haI~e, lrac8polyhal~e a"ld discortinuolJS day stringers.Clear to moderale reddiBh-brown hal~e, tr!lOllto Borne polyhal~e arl! trBCII 01 clay.Clear to moderate reddish-brown haI~e, trace tosome polyhal~e. anhydrite stringers nearbollom of un~.S55SSSSClear to grayish orange-pink halite.555SSSSH -t--"..:.'--1F.::.:L:::.::;::...==;:.:;::"'-=L.:=-="""'"=-'-...::=·_·a:,·-"........-'!'09Typical 5.5-m HighSimulated-WasteExperimental Room.. ~~y'~~~'~~ ..rlocally withanhydr~e.2.50 m2.01 m027 m~L r4m76Clear 10 r9ddish-oranga hame, trace polyhalle.2.13 mF... ; Ciea, hai~9: ir,ro; argila.>1oliS .432·L ___ r


The stratigraphic units described by Westinghouse(1989) are not encountered by all boreholes. however.As shown in detailed geologic maps of drift and roomribs (walls) throughout the underground facility (e.g.,Westinghouse, 1989, 1990). the halitie map units arelocally crosscut by syndepositional dissolution pits(Powers and Hassinger, 1985). These pits range indepth andwidth from a few centimeters to afew metersand maycompletely crosscutone or several map unitsat any given location. The pits are typically filled byrelatively pure, coarsely crystalline halite.As mentioned above, the halitic map units designatedby Westinghouse (1989) were defined on the basis ofrelatively consistent differences in clay content and/orcolor and polyhalite content that are apparent in macroscopieexamination.ratherthan on sedimentologicaldifferences. The local absence of map units can beattributed to depositional processes. Holt and Powers(1990) present a detailed discussion of the sedimentologyof the Salado Formation. They prOVide descriptionsof lithofacies commonly found within the Saladoand discuss syndepositional alteration processes.Salado textures and lithofacies distributions are highlyvariable both laterally (at a local scale) and vertically,as they are the products of repeated episodes ofdissolution and alteration over a large areal scale.6


3. TESTING EQUIPMENTThe following sections briefly describe the equipmentused in the permeability-testing program in the WIPPunderground facility.The equipment includesmultipacker test tools, data-acquisition systems, instrumentsto measure borehole deformation, pressuretransducers, and thermocouples.More detailed descriptionsof the testing equipment andthe proceduresand methods used to calibrate the equipment arepresented in Saulnier et al.(1991).NOTE: The use of brand names in this report isfor identification only, and does not implyendorsement of specific products by SandiaNational Laboratories.3.1 Multipacker Test ToolThe first two sets of tests performed under this program,in borehole C2H01, employed the multipackertest tool used for permeability tests in the wastehandlingshaft as described in Stensrud et al. (1988)and Saulnier and Avis (1988). This tool (Figure 3-1) isin principle very similar to the multipacker test tooldesigned specifically for the underground permeability-testingprogram, but lacks borehole-eleformationmeasuring devices. All other permeability tests wereconducted using the multipacker test tool describedbelow.The multipacker test tool designed for this testingprogram, shown on Figures 3-2 and 3-3, has twosliding-end, 9.5-cm outside diameter (0.0.) inflatablepackers mounted on a 4.83-cm 0.0. mandrel andoriented with the packers' fixed ends toward the bottom-holeend of the test tool. The packers have 0.92­m long inflatable elastic elements composed of naturalrubber and synthetic materials. The packer elementshave approximately O.81-m seal lengths when inflatedin 1O.2-cm diameter boreholes. The tool is anchoredto the wall or floor of the underground facility duringtesting by bolting a mandrel clamp to the flange of a0.51-m long borehole collar grouted into the top of thehole. For some tests, the test tool is also secured usingacross made of 1-mlengths of 5.08-cm square tubularsteel, which is clamped onto the mandrel or its extensionand anchored to the floororwall using 61-cm longrock bolts.Each multipacker test tool is equipped with three setsof ports to the bottom-hole test zone and the guardzone between the packers. One set of ports is used totransmit fluid pressures from the test and guard zonesto the transducers, which are mounted outside of theboreholes. A second set of ports is used to dissipate"squeeze" pressures created during packer inflationand to vent fluid from the isolated intervals to initiatepulse-withdrawal tests. These two sets of ports areaccessed by continuous lengths of OA8-em (3/16­inch) 0.0. stainless-steel tubing. The third set of portsprovides access forO.32-cm (1/8-inch) diameter TypeE thermocouples to measure temperatures in the testand guard zones. Packer-inflation pressures aremonitored with transducers attached to the packerinflationlines.The test-interval section of each test tool is equippedwith linear variable-differential transformers (LVOTs)to measure borehole deformation and test-tool movementduring the testing period. Three radially orientedLVOTs are located below the test-interval packer, andone axially oriented LVOT is mounted at the bottomend ofthe multipaekertesttool (Figure 3-3) to measuretool movement relative to the bottom of the hole duringtesting.3.2 Data-Acquisition SystemA computer-controlled data-acquisition system(OAS) monitors the progress of eaeh test and records7


Tw z0TEST -ZONE AND GUARD-ZONE VENT LINESDATA­ACQUISITIONSYSTEMFLOOR OR WALL OFUNDERGROUND FACILITYDATUM•GUARD-ZaNE-PACKERINFLATION LINE3/16-INCH (0.48 em)STAINLESS-STEELTUBINGGUARD-ZONEPACKERTw 00 z0 N0oc3/16-INCH(0.48 em)STAINLESS-STEELTUBINGEXTERNALLY MOUNTEDPRESSURE TRANSDUCERS10 MONllOR TEST-ZONEAND GUARD-ZONE FLUIDPRESSURE AND INFLATIONPRESSURE IN THE TEST -ZONEAND GUARD-ZONE PACKERSGUARD-ZONE 0 c:(0 ::JTRANSDUCER PORTTEST-ZaNE-PACKERINFLATION LINE3/16-INCH (0.48 em)STAINLESS-STEELTUBINGTEST-ZONEPACKERCJ1TEST -ZONE TRANSDUCER PORT0N0 t-CJ)Wt-IJ'_Figure 3-1.Multipacker Test Tool #1 Used in C2H01-A and C2H01-B Testing and in Waste-HandlingShaft Testing.8


TEST-ZONE AND GUARD-ZONEVENT LINESRADIAL AND AXIAL LVDT CABLES.....------,DATA­ACQUISITIONSYSTEMWALL/FLOOR OFREPOSllORYPACKERSLIDING ENDPACKERSLIDING ENDSPACERS(VARIABLE ----I~LENGTH)LVDT CARRIERI+ot-II!I-- EXTENSION HOUSING(VARIABLE LENGTH)GUARD-ZONE-PACKERINFLATION LINE3/16-INCH (0.48 em)STAINLESS-STEEL TUBINGv//~--GUARD-ZONE PACKER.- GUARD-ZONEL TRANSDUCER PORTTEST-ZONE-PACKERINFLATION LINE3/16-INCH (0.48 em)STAINLESS-STEELTUBING~-- TEST-ZONE PACKERf- @~--} RADIAL LVDT,3/16-INCH(0.48 em)STAINLESS­STEELTUBINGEXTERNALLY MOUNTEDPRESSURE TRANSDUCERS10 MONllOR TEST -ZONEAND GUARD-ZONE FLUIDPRESSURE AND INFLATIONT PRESSURE IN THETEST-ZONE ANDGUARD-ZONE PACKERSwzoN~ wf-w zoNo a:::3(J-L"'IIIt':::'W4I--- TEST -ZONETRANSDUCER PORTAXIAL LVDTFigure 3-2.Typical Configuration of the Multipacker Test Tools Designed for Underground Testing.9


TEST ZONEGUARD ZONEIf Needed,Extensions to Makethe Test Zone Longerare Added Herer = 4.754 emco10oo Qr = 4.413 emRADIAL LVDTsVENT IlNJECTIONPORTS ANDTHERMOCOUPLEACCESSPACKER --.--­ELEMENTr = 2.413 emor236.O em OFSTAINLESS-STEELINFLATION TUBING10 r = 0.238 emC'!o1~'


fluid-pressure, fluid-temperature, and boreholedeformationdata (Figure 3-4). Each DAS consists ofan IBM PS/2 Model 50 desktop computer for systemcontrol and data storage, and a Hewlett Packard (HP)3497A Data-Acquisition/Control Unit containing powersupplies to excite the transducers, thermocouples,and LVDTs, a signal scanner to switch and readchannels, and a 5-1/2 digit voltmeter to measure theoutput from the transducers, thermocouples, andLVDTs. The data-acquisition software allows samplingof the sensors' outputs at user-specified timeintervals ranging from 15 seconds to 24 hours. As thedata are acquired, they are stored both on thecomputer's hard disk and on either 3.5-inch or 5.25­inch diskettes. Real-time listing of the data on anauxiliary printer and screen and/or printer plots of theaccumulated data are also possible.3.3 Pressure TransducersFluid pressures in the test and guard zones and in thepackers are monitored with Druck PDCR-830 straingagepressure transducers rated to monitorpressuresfrom 0 to 14 MPa. The manufacturer's stated accuracyof the transducers is ± 0.1 % of full scale, or± 0.014 MPa. Transducers are calibrated before andafter each installation of a multipackertesttool accordingto procedures described in Saulnier et al. (1991).The transducers are mounted outside the boreholesand are connected to the isolated zones and thepackers through 0.48-cm (3/16 inch) O.D. stainlesssteeltubing, which passes into and through the packermandrels (Figure 3-2). Calibration data for the transducersused during the permeability testing discussedin this report are tabulated in Saulnier et al. (1991).3.4 ThermocouplesPickens et al. (1987) have shown that the thermalexpansion or contraction of fluid in an isolated testzone in a borehole can have a significant effect on themeasured fluid-pressure response during testing inlow-permeability media. Therefore, Type E Chromel­Constantan thermocouples are used to monitor temperatureswithin the test and guard zones during thepermeability tests, and these data are incorporated intest interpretation.The thermocouples used are0.32 cm (1/8 inch) in diameter, are sheathed in Inconel600, and are manufactured by ARI Industries. Thethermocouples are reported to be accurate to within± 0.006 °C. The thermocouples are calibrated bySandia National Laboratories, and the calibration dataare stored at the WIPP-site Sandia office.3.5 Linear Variable-DifferentialTransformersOpen boreholes, rooms, and drifts in the undergroundfacility exhibit closure, deformation, and differentialmovementbetween halite and anhydrite beds (Bechtel,1986). Measureable borehole closure (onthe order ofa few tenths-of-a-millimeter change in borehole diameter)in a shut-in, fluid-filled test interval could raise theflu id pressure to higherlevels thanwould occurwithoutthis closure. Axial movement of the multipacker testtool can be caused by packer inflation, fluid-pressurebuildup orwithdrawal in the isolated intervals, and holeelongation resulting from creep closure of the excavations.(The rate of rock creep decreases with increasingdistancefrom an excavation (Westinghouse, 1990),causing boreholes drilled from an excavation to elongate.)Axial movement of the test tool can change thetest-zone volume, which, in low-permeability media,can affect the observed flUid-pressure response in anisolated borehole interval.Three Trans-Tek Model241 LVDTs are radially mounted, with 120 0 separation,on the test-interval part of the multipacker test tool tomeasure radial borehole deformation (Figures 3-2 and3-3). These LVDTs can each measure a range ofmotionof 0.5cm. An axially mounted Trans-Tek Model245 LVDT on the bottom of the test tool measures toolmovement along the borehole axis (Figures 3-2 and3-3). This LVDT has a range of motion of 10 em. The11


___ 0_0_~__ O 0 0' 0 •• 0I---0_I 'I~~ SSURE-'­~r~,\NSDUCEI'~• ~LJL!::TSIVOl -­0\_ TLCTS---.! II: I~MQCOJPL.E­:::UTl EfSELECTRONICSCO:-;TROL PANEL.... : P20-0;>3 r40-00-003 040-0~1 02T1 T2 T30--0--011:> VAC AIR CONCITIONFR -liiiiiOi==il=i:1113M VGA CRT=-=--= ~-----~IBM;>S/2 COMPUTER~EXTERNALIBM St-INCH DISK DRIVE11 0 V:O"·~.3':'. II\CH-----F II-------'l----~ ·-T~DI~K DRIVE l-==- L~ PROPRIN~T, _1-"~-:TA~~~~i~~I~~- U gTn~ CONTRO:" UNIT _00o110 VAC VO:...TSURGE-SUPRESSORPOWER STRIPTHERMO-SNAPSWITCHI~O~;·o 0 0---.J KEPC10 ::l •.OWIER SUIPPL_YOAS ENCLOSURE -1'--__-__-__0 0JNI"lTERRUPT'BLEPOWER SUPPLY-_..,---~INI-POWI~E:RJA_!!li°~_1i!lCENTeR r --oBREAKERBOXI--- TRA~SFORMER480 VOLTSFigure 3-4.SChematic illustration of the Data-Acqu18lt1Dn System.12


LVOT responses are reported by Trans-Tek to belinear within ± 0.5% overtheir working ranges. Jensen(1990) discusses in detail the design, calibration, anduse of the LVOTs.3.6 Compliance-Testing EquipmentPickens et al. (1987) have shown thattest-tool movementin response to packer inflation and fluid injectionor withdrawal can affect fluid-pressure responses inisolated intervals in boreholes in low-permeabilitymedia. Figure 3-5 illustrates how packer movementdue to packer inflation can cause the packer elementto displace fluid in isolated intervals, causing changesin fluid pressure. Changes in the shape, volume, orposition of the test tool that affect fluid-pressure responsesduring testing are referred to as compliance.To evaluate the magnitude of compliance for themultipacker test tool, preinstallation compliance testswere conducted in the underground facility on all testtools according to procedures outlined in Section 4.1.Compliance tests were conducted in sealed and pressure-testedsections of 11.43-cm (4.5 inch) 0.0. steelor stainless-steel casing to differentiate test-tool-relatedphenomena from flUid-pressure responses observedin drilled boreholes. The casing was intendedto simulate a borehole with effectively zero permeability.Early compliance tests were conducted in the testrooms with the compliance chamber mounted on ajackstand from August 1988 through June 1989. Becausethe magnitude of diurnal temperature changesmonitored during early compliance tests in the steelcasing appeared to cause thermally induced f1uidpressureresponses, a stainless-steel chamber forsubsequent compliance tests wasplaced in a boreholedrilled into the Salado Formation from the undergroundfacility as shown on Figure 3-6.13


GUARD-ZONEBEFORECONFIGURATIONINFLATIONI ..GUARDZONE.. IVENTLINEINJECTIONLINEINFLATION LINE(TEST-ZONE PACKER)INFLATIONLINESLIDINGEND3/16-INCH (0.48 em) 0.0.STAINLESS-STEEL TUBINGAFTERINFLATIONSLIDING END OF TEST-ZONE PACKERMOVES INTO BOREHOLE WHEN INFLATEDVENTLINEINJECTION LINE LrL,-,....,INFLATION LINE(TEST-ZONEPACKER)INFLATIONLINE LrL'-"""SLIDINGENDFigure 3-5.Movement of Sliding-End Sub In Guard Zone During Packer Inflation.14


WALL''\I~-DATUMTEST-ZONEPACKERRADIAL LVDTsSTAINLESS-STEELCOMPLIANCE-TEST CHAMBERAXIAL LVDTFigure 3-6.Cross-Section View of Stainless-Steel Compliance-Testing Chamber in Borehole P4P30.15


4. TESTING PROCEDURESThe multipackertest tools are used to conduct permeabilitytests in boreholes drilled from the undergroundexcavations. In low-permeability formations such asthe Salado, changes in the volume or temperature ofthe test-zone fluid and/or the test tool can materiallyaffect observedfluid-pressure responses, as describedin Pickens et al. (1987). In addition, changes in fluidpressureconditions in isolated sections of boreholes inlow-permeability mediacan cause physical movementof the test tool. Changes in fluid-pressure conditionscan occur in response to temperature changes affectingthe test-zone and/or packer-inflation fluids. Fluidpressures in test intervals may also be affected bychanges in packer-inflation pressures, and vice versa,as when a pulse injection in a test zone increases theforces acting against the outside of the test-zonepacker, causing the packer-inflation pressure to increase.Changes in the volume and pressure of the test-zonefluid that are not due to the formation's hydraulicresponse but instead to changes in the position of thetest tool or deformation of the test tool or borehole areincluded under the term "compliance." Pickens et al.(1987) showed that compliance-related fluid-pressurechanges during permeability tests of formations withhydraulic conductivities less than 10- 12 mrs can obscureand/or dominate actual formation-related f1uidpressurechanges and result in incorrect estimates ofthe formation's hydraulic properties. Test-tool-relatedcompliance can be empirically estimated by subjectingthe testing equipment to simulated test conditions andobserving the resulting flu id-pressure responses. These"compliance tests" provide data to understand and/orcompensate fluid-pressure changes resulting fromcompliance during actual permeability testing.The multipacker test tool to be used for permeabilitytesting in any borehole undergoes compliance testingin a compliance-test chamber (Section 3.6) beforebeing installed in the test borehole. Compliance testingquantifies the response of the test tool to the typesand magnitudes of pressure changes anticipated duringpermeability testing. After compliance testing iscompleted, the test tool is installed in the test borehole,and a testing sequence consisting of a shut-in pressurebuildup followed by pressure-pulse tests is initiatedto evaluate the formation's hydraulic properties.Compliance- and pulse-testing procedures are discussedbelow.4.1 Compliance TestingCompliance tests are performed for each test toolbefore the tool is installed in a test borehole. Thepurposes of the compliance testing are to (1) establishthat the test tools have been properly assembled andthat all seals and fittings are performing as designed;and (2) evaluate test-tool responses to packer inflationand applied pressure pulses in the intervals isolated bythe inflated packers. During compliance tests, the testtools with all monitoring instruments are installed insteel or stainless-steel chambers sealed at one end inthe same manner employed when installing the testtool in a borehole. The DAS is used to monitor andrecord the results of the compliance testing.The test tool's packers are then sequentially inflated,starting with the test-zone packer. Both packers areinflated to between 8 and 10 MPa, after which thepressures are monitored for 24 to 48 hours for evidenceof leaks or improper performance. Packerpressures usually decrease during this period due tothe elasticity of the packer-element material, possible17


air entrapped during inflation going into solution, andother compliance-related phenomena. After monitoringthis pressure decline for the initial 24- to 48-hourperiod, packer-inflation pressures are usually increasedto 8 to 10 MPa and monitored for an additional 24 to 48hours.After the leak-checklpacker-pressure-adjustment periods,the test zone is sUbjected to a pressure-injectionpulse of at least 3.5 MPa. The fluid-pressure responsesof both the test and guard zones are thenmonitored for evidence of leaks, and the associatedpacker-pressure responses are also monitored. Afterevaluation of test-zone integrity is completed, thesame procedure is followed to evaluate the integrity ofthe guard zone.a small quantity of brine. The peak pressure quicklydissipated to about 4 MPa and then slowly decreaseddue to compliance effects such as packer readjustmentand/or axial test-tool movement. Figure 4-1 alsoshows that the guard zone received a pulse injectionon Day 227 when the pressure was increased fromoMPa to 5 MPa. The guard-zone pressure displayedsimilar behavior to that of the test zone. The pulseinjections into the test and guard zones caused pressurechanges throughout the system. As the pressurein a zone is increased, the adjacent packer(s) iscompressed, causing its internal pressure to increase.The packer(s) also deforms slightly away from thezone being pressurized, which can cause the pressurein the adjacent zone to rise slightly. This pressureincrease can in turn be transmitted to another packer.In some instances, the test- and guard-zone pressuresare increased and/or decreased in a series ofstep pressure-injection and/or -withdrawal pulses toprovide a range of test-zone and packer-pressureresponses to pressu re changes in neighboring zonesand packers. During the withdrawals, the volume offluid released during each pressure drop is measuredto provide data with which to evaluate test-toolor system compressibility.Figures 4-1 to 4-5 display the results of a typicalcompliance-test sequence. Figure 4-1 shows the fluidpressures in the test and guard zones; Figure 4-2shows the pressures in the test-zone and guard-zonepackers; Figure 4-3 shows the fluid temperatures inthe test and guard zones; Figure 4-4 shows the relativemovement of the radial LVDTs; and Figure 4-5 showsthe relative movement of the axial LVDT.During the compliance test depicted on Figures 4-1 to4-5, the pressure in the test zone was increased fromapproximately 0 MPat07 MPaonDay223byinjectingFigure 4-3 shows the temperatures measured in thetest and guard zones during compliance testing. Temperatureswere stable throughout the testing periodexcept for short-lived increases in the guard-zonetemperature following the pulse injections.Figures 4-4 and 4-5 show the LVDT responses duringcompliance tests. The radial LVDTs (Figure 4-4) showthat the test chamber's diameter in the test zoneincreased by about 0.04 mmduringthe pulse injection.This increase is consistent with the predicted diameterincrease calculated from the material properties of thetest chamber. Note that because of the LVDTs'orientation (see Section 3.5), the actual increase indiameter must be estimated by integrating the responsesof all three radial LVDTs. Figure 4-5 showsthat the axial LVDT was compressed (shortened)when the test-zone packer was inflated, but tended tolengthen as the test-zone-packer pressure declined.This response is probably due to some elastic responseof the packer element. During the pulseinjection in the test zone, the axial LVDT lengthened as18


8r-----r---"""T""---...-----,r------r---"'T"""---~--__,6ctl0-~Q)....::J(J)(J)4Guard-ZoneQ) 2Pulse Injection....a..0tPacker Inflation-2222 223 224 225 226 227 228 229 230Time (1989 Calendar Days)TR 1-6344-556-0Figure 4-1. Zone Pressures for Compliance Test COMP 16, Multipacker Test Tool #5,Borehole C2H03.1210Test-ZonePulse Injectionctl 80-::2-Q)6....::J(J)(J)Q)....0- 42PackerInflation","'Ooc:>-(lIoO-OO-C>O-1>


29.5 ,.-----r----r----..,------,;------r----r----,------,-0- Test Zone-0- Guard Zone29.0Test-Zone6" -- Pulse Injection~Q)...:::J"§ 28.5Q)0-EQ)f-28.0Guard-ZonePulse Injection27.5 L...-.__........L --L ......L -&.. ..L... ........ ""--__--..222 223 224 225 226 227 228 229 230Time (1989 Calendar Days)TRI-6344-558-0Figure 4-3. Zone Temperatures for Compliance Test COMP 16, Multipacker Test Tool #5,Borehole C2H03.E.3- 0.050c0.025Q)E 0.000Q)0!Q -0.0250-eni5 -0.050f-Cl> ....JE 5.080.3-en 5.075:::J:0 C'tl5.070 a:I I I In.--Test-Zone"( Guard-ZonePulse Injection / Pulse Injection7iIPackerInflation1·-- Test-Zone "'- Guard-ZonePulse InjectionPulse Injection-v~~-0- l VDT R-09-- Packer-l!r- l VOT R-07Inflation-0- l VDT R-06-4-- Radius-A-I5.065222 223 224 225 226 227 228 229 230Time (1989 Calendar Days)ITR 1-6344-559-0Figure 4-4. Radial-LVDT Data for Compliance Test COMP 16, Multipacker Test Tool #5,Borehole C2H03.20


0.081-0- LVDT A-03 10.06E~-c:Q)0.04EQ)0ctI,a.(J)(5 0.02f- Guard-Zone0 Packer Pulse Injection> --- Inflation.....J0.00-0.02 1...-__......L. .L...__--L ..I.-__---1 ....L.. .L--__-.J222 223 224 225 226 227 228 229 230Time (1989 Calendar Days)TRI-6344-560-0Figure 4-5. Axial·LVDT Data for Compliance Test COMP 16, Multipacker Test Tool #5,Borehole C2H03.the increase in test-zone pressure forced the test toolupwardinthe compliance-testing chamber. The guardzonepulse injectiondid not havethe same effect ontheaxial LVDT response.Saulnier et al. (1991) presentcomplete plots and tabulated data for the compliancetests performed before the permeabilitytests analyzedin this report.4.2 Pressure-Pulse TestingApermeability-testing sequence begins with the drillingof a nominal 1O.2-cm (4-inch) diameter borehole. Amultipacker test tool is installed in each test boreholeas soon after drilling as possible in an attempt tominimize pretest borehole history under noll-shut-inconditions.The test boreholes are filled with brinesaturated with sodium chloride, simulating the formationfluid, either immediately after drilling, or by injectingbrine through the injection lines after the packersare inflated. The fluid pressures and temperatures inthe isolated zones are monitored after test-tool installationuntilthe readings stabilize. The packers are thensequentially inflated to approximately 11 MPa, startingwith the test-zone packer. The packers are inflatedwith fresh water using a positive-displacement pressure-intensifierpump. The packer-inflation pressuresare monitored closely for 24 to 48 hours after inflation.If compliance-related reductions in the packer-inflationpressures of greater than 3 MPa are observed, thepacker-inflation pressures are increased to 11 MPaand observed for an additional 24 hours. After theinitial transient decreases in packer pressures occurand the packer-inflation pressures approach relativestability, valves on the test- and guard-zone vent linesare closed to shut in the test and guard zones.Once the test and guard zones are shut in, the fluidpressures in the two zones increase as they equilibratewith the formation pore pressure in the vicinity of the21


orehole. Pressure-pulse testing ofthe type describedby Bredehoeft and Papadopulos (1980) is initiatedafter the rate of pressure increase in the test zonedecreases and the pressure-recovery curve appearsto be on an asymptotic trend (Figure 4-6). Pulsewithdrawalrather than pulse-injection tests were generallychosen for the Salado Formation permeabilitytesting because: they do not force fluids into theformation that may not be in chemical equilibrium withthe rock; they do not overpressurize the formation, aprocedure which could potentially open existing fracturesor create new fractures by hydrofracture; andthey more closely represent the hydraulic conditionsexpected shortly after closure of the WIPP undergroundfacility when brine may be flowing from the hostrock towards the relatively underpressurized rooms.Pulse-withdrawal tests are initiated in a test or guardzone by opening the zone's vent valve and allowingfluid to flow from the zone until the desired fraction ofthe shut-in pressure has dissipated. After the desiredpressure decrease has been achieved, the valve isthen closed to shut in the zone. The volume of fluidreleased from the vent line during each pulse withdrawalis measured and recorded. Following the pulsewithdrawal, the reequilibration of the zone's fluid pressureand the formation pore pressure is monitored withthe DAS. After the zone's fluid pressure has recoveredto approximately its pre-pulse value, the test is usuallyrepeated (Figure 4-6) to provide assurance that theobserved fluid-pressure responses are reproducibleand are representative of formation responses. Aftertesting in the test zone (and guard zone if desired), thepressures in both the guard and test zones are ventedand the volumes of fluid produced during thedepressuring are measured before removing the testtool from the borehole. Forthe latertests, the pressurewas decreased in steps, measuring the volume releasedduring each step, to provide data with which toestimate the post-testing test-zone compressibility."ULSE-INJECTiON ~ \,TEST ' \,IDEA:- BEHAVIORFORMATIONPOREPRESSURE~-- OBSERVED INWIPP-S:TE LNDERGP,OUNDPERMEABILITY TESTINGPULSE-PULSE-I WITHDRAWAL I WITHDRAWALOPEN ---. .. t-I.(----·SH\..)T-I~, BUkDUP---- -~ TEST~ TEST ------TiME --_Figure 4·6.Typical Penneability-Testing Sequence.22


5. TEST LOCATIONS AND BOREHOLESFigure 5-1 shows the locations of the boreholes drilledfor the underground permeability-testing program.Boreholes were drilled in the experimental area, theoperations area, and the waste-storage area. Boreholelocations were chosen to provide access to differentSalado Formation lithologies (Figure 2-3), to investigatewhether or not the ages of excavations affectpermeabilijy in similar stratigraphic intervals, and toprovide a representative distribution of data from awide area of the underground facimy. The testingdiscussed in this report was performed in boreholesG2H01,G2H02,G2H03,N4P50,L4P51,SOP01,andS1 P71.Borehole locations in the underground experimentalarea (G2HOx, N4P50, and L4P51) were chosen toinvestigate three aspects of Salado Formation hydrology.First, holes drilled from Room G2, which wasexcavated stratigraphically above the waste-disposalhorizon, were used to test the waste-disposal horizonin downward-oriented boreholes. Second, boreholesdrilled from the stratigraphically higher parts of theexperimental area (Room G2) were usedto test MarkerBed 139 under conditions where it lies about sevenmeters below an excavation. (In contrast, Marker Bed139 is encountered about two meters below the excavationsin the operations and waste-storage areas.)Third, testing in the experimental area was conductedin boreholes drilled from excavations both older(RoomG2, North 1420 Drift) and younger (Room L4) thanthose in the waste-storage area.A borehole location in the operations area (SOP01)was chosen to allow testing of the strata in immediateproximity to the waste-disposal horizon from an excavation(South 1300 Drift) older than those available inthe waste-storage area, as well as to increase the arealdistribution of Salado hydraulic data.A borehole location in the waste-storage area (S1 P71in Room 7 of Waste Panel 1) was chosen to providehydraulic information for those portions of the SaladoFormation directly affected by the excavations scheduledfor waste storage (Figure 2-3). These areasgenerally have been exposed to excavation effects forless time than excavations in the experimental andoperations areas.In some instances, test tools are repositioned afterthe initial testing is completed to allow testing ofdifferent segments of holes. In other instances,holes are deepened and additional testing is performedafter testing of the initial borehole configurationhas been completed. In both cases, the firsttesting sequence performed in a borehole is givenan "A" suffix, as in G2H01-A, and subsequent testingsequences are given "B," "G," etc. suffixes, as inG2H01-B and G2H01-G. Note that only the "A"testing for boreholes L4P51 and S1P71 is discussedherein; later testing in these holes was not completedby the data-cutoff deadline for this report(February 1990).Permeability tests were not completed successfully inall boreholes drilled for the testing program. Theextremely slow fluid-pressure response observed inborehole C2H03 in Room C2 was considered unsuitablefor the continuation of testing activities. BoreholeN4P50, in the North 1420 Drift, had to be abandonedduring the shut-in period that normally precedes testingbecause of construction activities.A compressed-air drilling apparatus was used to drillthe boreholes for the permeability-testing program inthe floors and ribs (walls) of the test rooms. All of theboreholes were cored and/or drilled to a nominal10.2-cm (4 inch) diameter. The boreholes were cored23


-------------1379 m (4523 ft)---------------1RoomL4RoomC2ExperimentalArea.,I I: IN1100 DriftN1100 Drift=';:o~Air-IntakeShaftOperationsAreaWaste­StorageAreaNj•*Room a -_.-e::==: ::=~:=:===: ~ S90 DriftWaste-Handling~• Shaft 1552 mcor~;~:age - .".€::: ~ ~~rift (5091 ft)Typical Stora$le- 0 DOD 0 ExhaustRoom Dimensions ~ g Shaft(10m W x 4 m H x 91 m L) i ~ a:J d'p0P011 Room 7\ .•'300 DrillJtl[j[j~.'P7'Test Borehole LocationTesting UnderwayYet to Be ExcavatedPanelSPanel 7Panel 6Panel 5NOTE: Drift/Room WidthsAre Not to Scalel~i-=jj"-'ji:'ii=I"j="=lDDDD16000oDrioft DO J ~~~~~:II II II II II II IIII II II II II II II Panel 1l..!..-!.I=12: 1 ! -:! !.-!.I=!.I.:::._____________ DDDs~~~O_~r~f~ _11-11-11-11-11-11-1' -I -, - ~ 1-11-11-11-11-1'II II II II II II II I: I I : I I::I II I I II II II Panel 2II II II II II II II II II II I'll II II II II II'1_11_11_11_"-11-1 ,-_. _-I ~_ _ 1_..... _ .......1...11_1 ...11&,...;------------1'-1 - -,1-------------"_____________.JII':I_J .. _ _IIIL _11-11-,1-1 1-1 1-1 1-1 '--1--11- - .--' 1-11-11-11-11-11-11II II II II I' I' II .: II· :. II II II II II II II Panel 3II II II II I'll II II II II II II II II II II IIt!:-I I-I I-I 1_11_1 1-, !..._ ... _11 __.. 1_"'1_11_11_11_11_11_11------------1'-1 - -,1-------------"II I: II_____________ .J I_J .. _ _I L _1'-'1-11-"-11-11-1'-j --1'- -1--"-"-11-11-11-11-11II II II II II II II .: II : I : I II II II II II II Panel 4II II II II II II II II II II 1'1 II II II II IIL!.-!.I=~:I!-:!!.-.!.I=!.~':......._-.!.!...- -_..~=}.!':.I=-,!!,-.!.,=!.":I_"'!.l ---,L..1 ----776 m (2545 ft)------


when possible to allow sample recovery. When visiblequantities of formation brine were encountered inassociation with clay and/or anhydrite layers, brinesaturated with respect to sodium chloride was used asthe drilling fluid and conventional, non-coring drill bitswere used. For testing of C2H01-C, C2H02, C2H03,andL4P51, 12.7-cm(5inch) I.D.,51-cm (20 inch) long,steel borehole collars were grouted to the formation inthe tops of the holes. The multipacker test tools werethen botted to the collars to help eliminate test-toolmovement in responseto packer inflation and pressurebuildup in the guard and test zones. Borehole collarswere not used for earlier tests C2H01-A, C2H01-B,N4P50, SOP01, or S1 P71-A.Core samples were recovered from 95 percent of thedrilled lengths of the test boreholes. The lithologies,fracturing, penetration times, and occurrences of fluidwere recorded on the core sample logs (seeAppendix C,andSaulnieretal., 1991). The lithologiesare referenced to the standard WIPP map units listedin Appendix B. Descriptions of the drilling locationsand individual boreholes are presented below.5.1 Room C2Room C2 was excavated in March and April 1984 tonominal dimensions of 5.5 m wide, 5.5 m high, and34.8 m long (Bechtel, 1986). Figure 5-2 shows crosssectionand plan sketches of the borehole array drilledfor permeabilitytesting in RoomC2. Boththe initial anddeepened configurations for borehole C2H01 areshown. Borehole C2H01 was drilled vertically downwardto an initial depth of 5.58 m below the floor ofRoom C20nAugust4, 1988 (Calendar Day 217). Thefloor of Room C2 lies within map unit 7 (Figure 2-2),and the hole bottomed in map unit O. Thus, the holepenetrated all of the strata in which the waste-disposalrooms are located (Figure 2-3). The hole was deepenedt08.97mon February 13and 15, 1989 (CalendarDays 44 and 46) to allow testing of Marker Bed 139,which was encountered from 6.80 to 7.76 m. Adescription of the core samples recovered from boreholeC2H01 during both drilling periods is presented inAppendix C.Borehole C2H02 was drilled to allow testing of MarkerBed 139 beneath the rib (wall), rather than the floor, ofRoom C2. Borehole C2H02 was drilled westward, ata downward angle of 45' from the horizontal, to a depthof 10.86mfromthe intersection ofthe west rib and floor. of Room C2 (Figure 5-2). The drilled depth correspondsto a vertical depth of 7.68 m below the floor ofthe room. Borehole C2H02 was cored on April 12, 13,and 17, 1989 (Calendar Days 102, 103, and 107).MarkerBed 139wasencounteredfrom9.20to10.68 m(Figure5-2). The sectionofthe hole from 10.3 mtothebottom-hole depth of 10.86 m was cored using sodium-chloride-saturatedbrine to remove drilling cuttingsbecause formation brine was encountered whendrilling this interval. A description of the core samplesrecovered from borehole C2H02 is presented inAppendix C.Borehole C2H03 was drilled to test a bed of relativelypure halite between anhydrites "a" and "b" (Figure 5-2).The hole was cored horizontally, 2.1 m above the floor,into the west rib of Room C2 to a distance of 9.14 m.The drilling was performed on August 22 and 23, 1989(Calendar Days 234 and 235). A description of thecore samples recovered from borehole C2H03 is presentedin Appendix C.5.2 North 1420 DriftThe location of borehole N4P50 in the North 1420Drift is shown in Figure 5-1. This portion of the North1420 Drift was excavated in March 1983 to nominaldimensions of 6.1 m wide and 3.7 m high (Bechtel,1985). Borehole N4P50 was cored vertically downwardto a depth of 10.87 m below the floorof the drift(Figure 5-3) on December 15 and 16, 1988 (Calendar25


PLAN VIEW~s.sm--JillROOMC214.6mC2H031s. l 2m /2.13mUP Wall3O.5mC·~_C~~C :C~O,N1420 Drift(NOT TOSCALE)CLJWI~ROOMC2ANHYDRITE 'a'___ BOREHOLESM1--o1l-"':=========~9-.14-m-_-~--------~-~---""..-j/ 10.2_cmIDIAr-:;:.;;::::::.~:::; IANHYDRITE 'b' r r --LMARKER BED 139(ANHYDRITE WITHPOLYHALITE AT TOPAND CLAY E AT BASE)STRATIGRAPHICLOCATIONORANGE MARKER OF TYPtCAL3.84 m WASTEROOM-------a,,=__l-s.48m,- S.58mI ~: 6.80m 00 97.76m ~~I:;ff: b:~I 8.97 m ~ ,..--"- .... mBOREHOLEC2H01(DEEPENED)oI2I3I4ISCALE(Borehole diameter not to scale)5 METERSIWEST----- EASTFigure 5-2, Positions of Boreholes C2H01, C2H02, and C2H03 in Room C2,26


N1420DRIFTPLAN VIEW-z-----1.5 mROOM L416.8 mROOM 41(NOT TOSCALE)N1420 DRIFT...BOREHOLE10.2-cm DIAM.t~-------,++ ORANGEMARKER1.45mMARKER BED 139(ANHYDRITE WITH2.47 mPOLYHAUTE AT TOPAND CLAY E AT BASE)1---------..---- 4.83 mDEPTH (METERSIBELOW DRIFT FLOORCLAY DANHYDRITE ·c·1-::::::=========+= 10- 10.13 10.24 m--------+- 10.87 mCLAY Bo 2 3 4 5 MEl ERSI I I I ,SCALEIBOfehole diameter not to scalelNORTH----- SOUTHFigure 5-3.Position of Borehole N4P50 in the North 1420 Drift.27


Days 350 and 351). The borehole was drilled toallowtesting of anhydrite "c,"which was encounteredfrom 10.13 to 10.24 m deep. A description of thecore samples recovered from borehole N4P50 ispresented in Appendix C.5.3 Room L4Room L4 was excavated in February 1989(Westinghouse, 1990) and provided an opportunity toinstall and test a borehole shortly after a room hadbeen excavated. The room is nominally 10.1 m wide,3.7 m high, and 59.7 m long. Borehole L4P51 wasdrilled and cored vertically downward to a depth of4.75 m below the floor of the room (Figure 5-4) fromOctober 18 to 19, 1989 (Calendar Days 290 and 291).The borehole was drilled to investigate the propertiesof Marker Bed 139 and the underlying halite, polyhalitichalite, and clay D. Marker Bed 139 (including clay E)was encountered from 1.50 to 2.36 m below the floorof the room, and clay D was encountered from 4.55 to4.57 m deep (Figure 5-4). A description of the coresamples recovered from borehole L4P51 is presentedin Appendix C.5.4 South 1300 DriftFigure 5-1 showstheiocationofborehoieSOP01 intheSouth 1300 Drift. This portion of the South 1300 Driftwas excavated in June and July 1984 to nominaldimensions of 6.1 m wide and 3.7 m high (Bechtel,1985). Borehole SOP01 was drilled on January 11 and12, 1989 (Calendar Days 11 and 12) to investigateMarker Bed 139 and the underlying halite, polyhalitichalite, and clay D in a location between the experimentalarea and the waste-storage area. The hole wasdrilled vertically downward to a depth of 5.17 m belowthe floor ofthe drift (Figure 5-5). The ho Ie encounteredMarker Bed 139 from 1.80 to 2.76 m below the floor ofthe drift. Clay D was encountered at the bottom of theborehole, from 5.155 to 5.170 m (Figure 5-5). Adescription of the core samples recovered from boreholeSOP01 is presented in Appendix C.5.5 Waste Panel 1, Room 7Room 7 in Waste Panel 1 was excavated in March1988 to nominal dimensions of 10.1 m wide, 4.1 mhigh, and 91.4 m long (Westinghouse, 1989). BoreholeS1 P71 was drilled vertically downward into thefloor of Room 7 (Figure 5-6) on November 10, 1988(Calendar Day 315) to a depth of 4.56 m. The purposeof the hole was to allow testing of Marker Bed 139 andunderlying halite, polyhalitic halite, and clay D in thewaste-storage area. Borehole S1 P71 encounteredMarker Bed 139 and clay E from 1.40 to 2.25 m belowthe floor of Room 7 (Figure 5-6). Clay D was encounteredat the bottomofthe borehole. A descriptionof thecore samples recovered from borehole S1 P71 duringdrilling is presented in Appendix C.28


IT46.9 m-r-10.1m~ROOM L4...1---+_. L4P511.-1.5 mPLAN VIEW~NI(NOT TOSCALE)ROOM L4+ ++ + ORANGE MARKERBOREHOLE10.2-cm1..-----------'DIAM._1.S0m2.36 mMARKER BED 139 (ANHYDRITEWITH POLYHAUTE AT TOPAND CLAY E AT BASE)DEPTH (METERS)BELOW ROOM FLOOR4.75 m-~---~-------4.55 mCLAY Do 2 3 4 5 METERSI I I I ISCALE(Borehole diameter not to scalelWESTEASTFigure 5·4. Position of Borehole L4P51 in Room L4.29


PLAN VIEWE300 DRIFT-z S1300 DRIFT1SOP011.2 m~• ]J19.2 mAIR-FLOWBULKHEAD5.6 mE140 DRIFT(NOT TO SCALE)S1300 DRIFT++BOREHOLE10.2-cm DIAM.-.-+ ORANGE MARKERDEPTH (METERS)BELOW DRIFT FLOORMARKER BED 139(ANHYDRITE WITHPOLYHAUTE NEAR TOPAND CLAY E AT BASEl-----'-----'-----....------5.17 mCLAY DoI2I3I4ISCALE(Borehole diameter not to scale)5 METERSINORTH----- SOUTHFigure 5·5.Position of Borehole SOP01 In the South 1300 Drift.30


PLAN VIEWPANEL 1 ROOM 7tNjSlP71.1.5 m-J I--I111.2 m~10.1m59.1 m(NOT TOSCALE)ROOM 7 WASTE PANEL 1BOREHOLE1O.2-cm DIAM.ORANGE MARKERMARKER BED 139(ANHYDRITE WITHPOLYHALITE AT TOPAND CLAY E AT BASEln::-0~9~ILw:;::;:0-0f-In::CLAY D '-. 0- s:-----------~,,---.--JL---'- 4.56 m ~ §(])o 1 2 3 4 5 METERSLJ_~~-,l~SCALE(Borehole diameter not to scale)WEST----- EASTFigure 5-6. Position of Borehole S1 P71 In Waste Panel 1, Room 7.31


6. INTERPRETATION METHODOLOGYInterpretation of the permeability tests in the WIPPunderground facility was performed with the well-testsimulationmodel GTFM (~raphlheoreticEieIdModel;Pickens et aI., 1987). GTFM was used to simulate thefluid-pressure responses observed during permeabilitytesting of the Salado Formation. Different combinationsof the most uncertain formation parameters,hydraulic conductivity and pore pressure, were used inthe simulations. Estimates of the actual values ofthese parameters were determined by graphicallycomparing the simulated and observed fluid-pressureresponses. The parameter combinations that yieldedthe simulated responses that most closely matchedthe observed fluid-pressure responses were consideredto be representative estimates of the actualformation parameters. The simulation model was alsoused to conduct sensitivity analyses of the most importantmodel and formation parameters to quantify theuncertainties of the formation-parameter estimates.The well-test-interpretation model is discussed in Section6.1. Section 6.2 summarizes some of the salientassumptions underlying the test interpretations. Section6.3 discusses the values of the tested formations'material properties that were used in the simulationsand how those values were selected.The primary parameters used by the analysis model tosimulate the formation's fluid-pressure responsesduring pulse tests are the formation's hydraulicparameters, the test-zone volume, and the test-zonecompressibility. The test-zone volume and test·zonecompressibility are used to calculate the wellboreboundary conditions for the pulse-test simulations.Section 6.4 presents the initial test-zone volumes usedfor each interpreted test and the procedure used tocompensate the simulations for variations in test-zonevolume during testing. Section 6.5 discusses theprocedures and rationale used for determining testzonecompressibility. Section 6.6 discussesincorporation of the observed test- and guard-zonetemperature data in the simulations.6.1 Well-Test-Simulation ModelGTFM is a numerical model that simulates the hydraulicresponse of a single-phase, one-dimensional, radial-flowregime to boundary conditions applied at aborehole located at the center of the modeled flowsystem. The problem domain is discretized by dividingthe radial-flow system into a series of concentric ringscentered on the borehole, with each ring representedby a node. A constant multiplicative factor is used toincrease the spacing between nodes with increasingdistance from the origin (borehole). For the simulationspresented in this report, 250 radial nodes wereused. The model assumes that the formation has aconstant thickness with vertically homogeneous hydraulicproperties.Formations maybe single ordoubleporosity, and may include a single radially centeredheterogeneityto simulate the presence of a "skin" zoneadjacent to the borehole. The skin zone may haveproperties different from those of the remainder of theformation.The GTFM model can be used with assignedconditionsof either fixed pressure or zero flow at the externalboundary of the model. Selection between the twoboundary conditions is made on a test-specific basis,depending on whether or not the test data showboundary effects. If no boundary effects are indicatedby the test data, a fixed-pressure boundary conditionis specified at a distance from the borehole such thatthe type of boundary has no effect on the calculatedfluid-pressure response in the borehole. The adequacyof the specified distance is verified by ensuring that thepressure in the portion of the simulated formation33


adjacent to the boundary does not change over theduration of the test-interpretation simulation. In caseswhere boundary effects are indicated, the type of, anddistance to, the boundary are parameters selected andfitted as part of the test interpretation.The model has wellbore boundary conditions whichcan be used to simulate pulse-injectionlwithdrawaltests, specified borehole-pressure conditions, specifiedformation flow rates, and slug-injectionlwithdrawal tests.The effects of consecutive tests are incorporated in thesimulations. The model can also incorporate test-zonepressure changes resulting from temperature variationsin the test zone as well as test-equipment- and/orformation-induced changes in the test-zone volume.The model output consists of simulated fluid-pressureresponses in the borehole and at selected radialdistances from the borehole. The model can alsocalculate formation flow-rate data and cumulativeproductiondata based on the formation's estimatedhydraulic properties.For the interpretations presented in this report, theindividualtesting periodswere subdivided into discretetime intervals, called sequences. Sequences weredifferentiated by the wellbore boundary conditions ineffect during these time periods. History sequenceswere used to represent the test intervals' pretestborehole-pressure history during the open-boreholeperiod between drilling and initial shut-in of the testzone, and also to represent time periods when nonidealbehavior characterized the fluid-pressure responses.During history sequences, the pressureconditions in the isolated test intervals were specifieddirectly using the fluid pressures recorded by the DAS.Pulse sequences were used to simulate the fluidpressurebuildups observed after shutting in the testzones and also the fluid-pressure-recovery responsesto individual pulse-injection and pulse-withdrawal tests.A complete description of the methodology, appropriateboundary conditions, and governing equations ofthe model can be found in Pickens et al. (1987). GTFMwas verified by comparing its results to analyticalsolutions for pulse tests, slug tests, constant-pressureflow tests, and constant-flow-rate pumping tests(Pickens et aI., 1987).Application of GTFM to thesimulation of pressure-pulse testing in low-permeabilityformations is described in Saulnier and Avis (1988).Assumptions inherent in the formulation of GTFM andapplication of the model to the Salado permeabilitytestingprogram are described in Section 6.2 below.6.2 Assumptions Used in TestAnalysisThe analysis of the Salado Formation permeabilitytests assumed a one-dimensional radial-flow regimeon the scale of testing.For the majority of the testsdiscussed in this report, the boreholes were vertical,and therefore radial flow was the same as horizontalflow. Radial flow was also assumed forthe analysis ofthe tests in the nonvertical holes C2H02 and C2H03.The implications of this assumption forthe nonverticalholes are discussed with the relevant test interpretationsinSections7.1.4.1(C2H02) and7.1.5.1 (C2H03).The assumption of one-dimensional radial flow requiresjustification with respect to the flow dimensionincluded (horizontal, or parallel to bedding) and to theflow dimension excluded (vertical, or perpendicular tobedding). With respect to the horizontal dimension, anassumption of radial flow implies that the formation ishomogeneous and isotropic in the horizontal planeover the volume tested.Even though no medium isever truly homogeneous or isotropic on a microscopicscale, this is nevertheless a standard assumptionunderlying most analytical methods forsingle-welHestanalysis. The assumption of horizontal homogeneitymeans thatthe permeability of the volume being tested34


will not change appreciably if the volume is increasedor decreased slightly. The assumption of horizontalisotropy is acceptable in a horizontally anisotropicmedium if the interpreted permeability is recognized asbeing an effective permeability (Le., the square root ofthe product of the minimum and maximum permeability[Hantush, 1966]).With respect to a potential vertical flow direction, anassumption ofone-dimensional radial flow implies thatvertical flow is either nonexistent or is of such lowmagnitude that ~ has no appreciable effect on theradial flow field. For eitherof these cond~ions to exist,the vertical permeabilities of the strata above andbelow the test interval must be much less than thehorizontal permeability within the test interval, to prevent(or minimize) vertical flow from above and belowinto the test interval. Most of the tests discussed in thisreport were performed over intervals with arbitrarilydefined tops and bottoms which did not coincide withlithologic discontinuities but were instead defined bythe physical dimensions of the test tools. Thus, thepotential for vertical flow is limited solely by the anisotropyin permeability of the host rock between thehorizontal and vertical directions. Unfortunately, noinformation is available on the presence or absence ofhorizontal-to-vertical permeabil~y anisotropy in evaporites.In most sedimentary porous media, this type ofanisotropy is imparted to the rock by the stratificationof clastic material. For example, when tabular clayminerals are oriented with their long axes parallel tobedding and their short axes perpendicularto bedding,the resulting arrangement of overlapping plates tendsto reduce permeability in the direction perpendiculartobedding (Freeze and Cherry, 1979). Whetheror not asimilar mechanism is effective at producing anisotropyin evapor~esis unclear, however, because the permeabilityof the evaporites may already be as low or lowerthan the permeability of clays perpendicular to bedding.The permeability of clays parallel to bedding,however, is probably higherthan that of evaporites, inwhich case clays may still impart anisotropy to theoverall medium, at least on the scale at which the claysformacontinuous interconnected layer. Giventhe lackof quantitative information on anisotropy in evaporites,the potential effects of vertical flow were excluded fromthe preliminary analyses presented in this report. Ingeneral, ignoring potential vertical flow, which contributesto observed pressure-recovery rates, should resultin overestimates of horizontal permeability. Sensitivityanalyses will be performed at a later date toevaluate the potential errors associated with this exclusionas a function of the magnitude of anisotropy.Another model assumption is that the hydraulic headin the test horizon is static (constant w~h time), andradially and longitudinally (parallel to the boreholeaxis) invariant before drilling begins. Preliminary evidencefrom a limited nu mberof holes indicates that thepressures under the floor of a room are less than thepressures under the ribs (walls). The resulting pressuregradients may reflect dilatation of the rock beneathrooms as a result of the excavation of the rooms(see Section 7.3.1) or flow to the rooms. Thesegradients appear to persist over longer time scalesthan those of the permeability tests. Thus, the pressure responses to the permeabilitytests may be superimposedon a relatively static pressure field. In anycase, lacking reliable two-dimensional definition of thepressure distribution overtime within a tested horizon,our initial assumption in modeling will be that a singleconstant pressure exists throughout a tested horizonwhen testing begins. As more data on pressuredistributions become available, two-dimensional modelingwill be performed to evaluate the influence of thisassumption on the test interpretations.Considering the proximity of excavations at atmosphericpressure to the test intervals, longitudinalpressure gradients through the test intervals toward35


the excavations should be present.The fluid pressuresobserved during testing, therefore, probablyrepresent the average pore pressures (heads) overthe entire tested intervals.Treating these averagepressures as if they were uniformly distributed overthetested 1- to 2-m thicknesses is not expected to lead tosignificant errors during test interpretation.Other assumptions specific to the interpretation ofindividual tests are discussed in Section 7.1 under theheadings of the individual tests.6.3 Material Properties Used inTest SimulationsTo simulate permeability tests using GTFM, a numberof material properties must be specified.Theseproperties include the porosity, elastic moduli, andpermeability (hydraulic conductivity) ofthe IithoJogy(ies)being tested; the compressibility and density of theformation brine; and the thermal-expansion coefficientof the test-zone brine.Porosity, elastic moduli, andbrine compressibility and density are used to calculatethe specific storage of the formation.The thermalexpansioncoefficient is used to incorporate the effectsof variations in test-zone temperatures on test-zonepressures.Most of the values of these material properties can bereliably estimated to within an order of magnitude orless. Permeability is the most uncertain of the parametersand, therefore, permeability is used as one of theprimary fitting parameters during the model simulations.Other, more certain, parameters are simplyspecified as constants. The values used in the simulationsfor the different material properties are presentedbelow along with discussions of the methodsused to determine orto estimate those values. Sensitivitycalculations performed to evaluate the significanceof uncertainties in both the specified and fittedparameters are presented in Section 7.2.6.3.1 FORMATION POROSITY. A review of the SNLtesting of samples from the formations at the WIPPsite, as presented in Touloukian et al. (1981), Powerset al. (1978), Black et al. (1983), and Skokan et al.(1989), indicates that a porosity of 0.01 is representativeof the Salado Formation halite and anhydriteinterbeds. Porosities presented in the referenceslisted above range from 0.001 to 0.03. Althoughfracturing and/ordiagenetic changes may have locallyadded secondary porosity to anhydrite interbeds suchas Marker Bed 139, this added secondary porosityprobably does not alter the range of porosities presentedabove.6.3.2 FORMATION ELASTIC MODULI. Elastic moduliof the halite and anhydrite lithologies tested have beenreported by Wawersik and Hannum (1980), Pfeifle andSenseny (1981), Teufel (1981), Gevantman (1981),Krieg (1984), and Desai and Varadarajan (1987).These moduli are summarized in Table 6-1. NoSalado-specific dataon the elastic moduli of claystoneare available. The claystone moduli presented inTable 6-1 are reported by Pfeifle et al. (1983) formudstones from the Palo Duro Basin in Texas. Thevalues presented by Krieg (1984) and the averages ofthe values from Pfeifle et al. (1983) were taken asbase-ease values, with the other sources or individualvalues providing the ranges of values to be used insensitivity analyses (see Section 7.2.4).6.3.3 BRINE COMPRESSIBILITY. The compressibilityof brine depends on pressure, temperature, fluidcomposition, and gas saturation. In general, fluidcompressibility decreases with increased pressureand dissolved-solids concentration, and increaseswithtemperature and the amount of dissolved gas.Two brines were used as the test-zone fluid for thetesting in the WIPP underground facility. Brine forthetesting in C2H01-A, C2H01-B, and S1 P71-A was36


Table 6·1Reference Elastic Moduli of Salado LithologiesYoung's Modulus Poisson's Ratio Bulk Modulus Shear ModulusE (GPa) v K (GPa) G (GPa)Base Base Base BaseRock Type Base Value Range Value Range Value Range Value(,)-.,JHalite' 20.7 - 36.5 31.0 0.17 - 0.31 0.25 15.0 - 21.7 20.7 8.1 -15.6 12.4Anhydrite 2 59.0 - 78.9 75.1 0.31 - 0.42 0.35 68.1 - 85.0 83.4 21.4 - 30.4 27.8Claystone 3 2.2 - 9.4 5.3 0.25 - 0.34 0.30 2.0 - 6.7 4.4 0.8 - 3.8 2.1,Data from Wawersik and Hannum (1980), Gevantman (1981), Krieg (1984), and Desai and Varadarajan (1987)2Data from Teufel (1981), Pfeifle and Senseny (1981; Salado values only), and Krieg (1984)3Data from Pfeifle et al. (1983)


obtained from Rowland Trucking of Carlsbad, who useCarlsbad city water to dissolve Salado halite to asclose to saturation as possible. The total-dissolvedsolids(TDS) concentration of this brine is approximately320,000 mglL (Data supplied by B&E, Inc.,Carlsbad). The brine used in all other test boreholeswas supplied by the WIPP Brine Sampling and EvaluationProgram (BSEP). Brine for testing in SOP01,C2H01-C, C2H02, C2H03, and N4P50 was obtainedfrom borehole DHP-402A in Room 7, Waste Panel 1.The brine used in testing in borehole L4P51-A wasobtained from boreholes drilled in the entryway of theunderground core library. The dissolved-solids concentrationof brine supplied by the BSEP was about380,000 mglL (Deal et aI., 1989).The compressibility of saturated sodium-chloride brinewith dissolved-solids concentrations approximatelyequal to those collected under the BSEP was estimatedusing Figure D.19 in Earlougher (1977), whichplots fluid compressibility versus temperature for brinescontaining 300,000 parts per million (ppm) NaCI dissolvedin distilled water at various pressures andassuming no solution gas. Forthe limited temperaturerange of 26° to 29°C observed during the underground-permeability-testingprogram at WIPP, the formation-brinecompressibility can be assumed to beessentially invariant and insensitive to temperature.For the pressure ranges observed during testing, fluidcompressibility at 27°C interpolated from the curvesshown on the figure ranges from 2.75 x 10- 10 Pa- 1 at9.8 MPa to 3.1 x 10. 10 Pa- 1 at 2.5 MPa.The fluid compressibility derived from Earlougher(1977)assumes brine with no dissolved gas. Earlougher(1977) further shows that the compressibility of watersaturated with methane at 25°C is about 5 to 12percent higher over a pressure range from 2.5 to 9.8MPa than that ofthe same water with no dissolved gas.Gas present in the Salado Formation is largely nitrogen,rather than methane (U.S. DOE, 1983). However,Cygan (1991) showed that nitrogen solubility inbrine is slightly lowerthan that of methane. Therefore,the effect of dissolved nitrogen on brine compressibilityshould be slightly less than the effect of dissolvedmethane. Based on these data, we estimate that theamount of gas potentially in solution at the pressuresobserved during the permeability tests might increasethe compressibility of the gas-brine solution by amaximum of about ten percent.After consideration of the foregoing information, asingle formation-fluid-compressibility value of 3.1 x10- 10 Pa- 1 was selected for use in all test interpretationspresented inthis report. This value was consideredto be representative of actual in situ formationbrine given the limited range of variability of thedensity and dissolved-solids concentration of formationbrine and the lack of quantitative data regardingsolution-gas constituents.6.3.4 FORMATION BRINE DENSITY. Saladobrine densities reported by the WIPP BSEP rangefrom 1.215to 1.224 kglL (Deal et aI., 1987). Forthisstudy, formation brine density was approximated as1.22 kg/L.6.3.5 ESTIMATION OF SPECIFIC STORAGE.Specific storage is defined as the volume of waterreleased from storage by a unit volume of aquiferbecause of expansion of water and compression of theaquifer under a unit decline in hydraulic head (Hantush,1964). The expression for specific storage mostcommonly used in groundwater hydrology is as givenby Domenico (1972):(6-1 )38


where:P fgafluid densityacceleration of gravityvertical formation compressibility formation porosityf3fluid compressibilityImplicit in this equation is an assumption that thecompressibility of the rock solids is a negligiblecomponent of the bulk formation compressibilitycompared to the compressibility of the pores.Thisassumption is valid for most aquifer materials, whichhave porosities on the order of a few tens of percentand low-compressibility solids. This assumption maynot be valid for halite, however.Green and Wang (1990) present a rigorous expressionfor specific storage that includes the bulk modulus(inverse of compressibility) of the rock solids:_ [( 1 1)( 4G(1-K/K s )/3) (1 1)]Ss -PIg --- 1- + ---K K s K+4G / 3 K I K swhere:P fgKfluid densityacceleration of gravitydrained bulk modulus of rock(6-2)K. unjacketed bulk modulus of rock (grain orGsolids modulus)drained shear modulus of rock porosityK fbulk modulus of fluidWhen the K. term in Eq. 6-2 is much greater than theK term (KlK. '= 0), Eq. 6-2 reduces to Eq. 6-1 (Greenand Wang, 1990) with:a = l/(K + 4G/3) (6-3)Few data are available on the bulk modulus of halitesolids, andthose datathatare available are not specificto Salado halite. Carmichael (1984) lists 15 values,ranging from 22.8to 24.0 GPa, forthe bulk modulus ofhalite solids. These values are only slightly higherthanthe values for the drained bulk modulus (K) of Saladohalite given in Table 6-1 (15.0t021.7GPa). Thus, if thedata from Carmichael (1984) are also representativeof Salado halite, KlK. :#0, and the specific storage ofSalado halite is probably better represented by Eq. 6-2than by Eq. 6-1.Using Eq. 6-1 and the base-case mechanical propertiesof halite given in Table 6-1 ,the specific storage of halitewith a porosity of one percent is about 3.6 x 10- 7 m- l •Using the same parameters in Eq. 6-2, along with abulk modulusof halite solids (K.) of 23.4GPa, producesa specific-storage estimate of about 9.5 x 10- 8 m l .Thus, the specific storage calculated using Eq. 6-2 isabout a factor of four smaller than the specific storagecalculated using Eq. 6-1 .No datawere available onthebulkmodulusof anhydritesolids. Consequently, the specific storage of anhydritewas evaluated using Eq. 6-1 and the base-casemechanical properties presented in Table 6-1. Thespecific storage of anhydrite with a porosity of onepercent is about 1.4 x 10- 7 m l .Palciauskas and Domenico (1989) note that porecompressibility accounts for 95 to 100 percent of thebu Ik compressibilityof mudstone andclay. Accordingly,the specific storage of claystone was evaluated usingEq. 6-1 and the base-case elastic moduli presented inTable 6-1. The specific storage of claystone with aporosity of 30 percent was thereby calculated to beabout 2.8 x 10- 6 m l •39


In cases where the tested interval included severallithological intervals having different elastic moduli, alength-weighted average was used for specific storage.Table 6-2 lists the estimated specific-storage valuesfor the formations tested and shows the weightingused to arrive at those estimates.6.3.6 THERMAL-EXPANSION COEFFICIENT OFTEST-ZONE BRINE. The thermal-expansioncoefficient of the test-zone brine was estimated fromdata showing the density of pure water as a function oftemperature (Weast, 1983) and data showing therelationship of sodium-chloride solution density as afunction of salt concentration and temperature (Perryand Chilton, 1973). These data were used to calculatethe thermal-expansion coefficient of water for a rangeof temperatures and solution concentrations. For thebrines used and the range of temperatures observedduring the brine-permeability testing program, thecoefficient of thermal expansion (C ) Twas estimated tobe 4.6 x 10-4 aC-1. This value of C Twas also used byNowak et al. (1988) in modeling brine inflow to theWIPP underground facility.6.4 Test-Zone VolumeAccurate knowledge of the volume of fluid containedwithin a test zone is important in the interpretation ofpermeabilijy tests in packer-isolated test intervals.Table 6-2Specific Storage Values Used in Test InterpretationsLithologies and Lengths (em)Test-ZoneAverageTest ID Length (em) Halite Anhydrite Clay Specific Storage (m-')aC2H01-A 349 349 0 0 9.5 X 10- 8C2H01-B 108 108 0 0 9.5 X 10- 8C2H01-B-GZ 110 110 0 0 9.5 X 10- 8C2H01-C 234 138 96 0 1.4 x 1O- 7bC2H02 139 51 88 0 1.4 x 1O- 7bC2H03 138 138 0 0 9.5 X 10- 8L4P51-A 142 140 0 2 1.3 X 10- 7SOP01 143 142 0 1 1.1 X 10- 7SOP01GZ 105 15 90 0 1.4 X 1O- 7b81 P71-A 144 141 0 3 1.5 X 10- 7aAverage specific storagebHalite sections ignoredAverage is length-weighted average based on mhology, except as noted:LithologyHaliteAnhydriteClay seams (claystone)Specific Storage(m- 1 )9.5 X 10- 81.4 X 10- 72.8 X 10- 640


Together with the test-zone compressibility(Section 6.5), the test-zone volume controls the amountof fluid that must flow into or out of the test zone tocreate a given fluid-pressure change. The techniquesused to estimate the test-zone volume at the start ofeach test and the changes in test-zone volumes thatoccurred during the tests are discussed below.6.4.1 INITIAL TEST-ZONE VOLUME. The initial testzonevolume, Vtz(O), refers to the volume of fluid in thetest zone when the test zone was isolated at the startof the initial fluid-pressure build-up period after packerinflation. Vtz(O) plus ~Vtz(t), the volume-compensationfactor discussed in Section 6.4.2, are used to calculateVtz(t). Vtz(t) and test-zone compressibility are used tocalculatethe wellbore boundary condition applied du ringthe simulation of pulse tests.all test zones were considered to be one cm longer,and all guard zones were considered to be two cmlonger, than the lengths indicated on the test-toolconfigurationdiagrams. Second, the sliding end of apacker was observed to move 5.7 cm during inflationin slotted steel casing. On multipacker test tool #1,used forthe C2H01-A and C2H01-B testing, the slidingend of the test-zone packeris in the test zone, while thesliding end of the guard-zone packer is on the sideaway from the guard zone. Thus, the test zone formultipacker test tool #1 is about six cm longer afterpacker inflation, while the guard-zone length does notchange. For multipacker test tools #2-5, used for allothertesting, the sliding end of the test-zone packer isin the guard zone. Thus, the guard zones for theseothertest tools lengthen by about six cm during packerinflation, while the test-zone lengths remain unchanged.The test-zone volume used for each simulation wasestimated by subtracting the test-tool volume from thevolume of the isolated length of the borehole:(6-4)where:Vtz(O) initial test-zone volumeVhole(O) initial borehole volumeVtool(O) initial test-tool volumeTo calculate an initial test-zone volume, the length andradius of the test zone must be known. The test-toolconfigurationdiagrams presented in ChapterS indicatethe lengths of the test and guard zones after the testtools have been installed in the boreholes, but beforethe packers have been inflated. Two corrections mustbe made to these lengths to represent actual testconditions. First, based on a cast made of the end ofa packer when it was inflated in steel casing,approximatelyone cm at the end ofthe packerelementsdoes notseal againstthe wall of the casing. Accordingly,Initial borehole-radius values were calculated fromthe data derived from the radial LVDTs when theborehole test intervals were first shut in. (The initialshut-in values of the radial LVDTs were assumed toreflect the actual borehole radius because they wereobtained before fluid-pressure bUildup in the testintervals could compress the O-rings of the LVDTs,as described in Section D.2 of Appendix D). Theradii calculated from the radial-LVDT data rangefrom 5.119 to 5.225 cm, which are larger than the5.08-cm nominal radii of the core bits used in drillingthe test boreholes. The apparent enlargement of theboreholes is probably due to the impact of the drillrods on the borehole walls after the core bits hadexposed the relatively soft evaporite minerals in theboreholes. For the C2H01-A and C2H01-B tests,where no radial LVDT datawere available, a boreholeradius of 5.2 cm was used in all calculations.The test-tool volumes were estimated from dataobtained by immersing multipackertesttool #3 inwaterin a length of sealed and volumetrically calibrated41


transparent casing. The volumes of multipacker testtools #2, #4, and #5 were estimated using the volumedisplacementdata from multipacker test tool #3, andcompensating for different lengths of the various toolcomponents of the different tools.Table 6-3 presents calculated borehole volumes, testtoolvolumes, and initial test-zone volumes used in thepermeability-test simulations presented in this report.The calculated borehole volumes, and therefore testzonevolumes, must be considered uncertain becausewe have assumed perfectly cylindrical holes with radiiexactly as indicated by the radial LVDTs. Thisuncertainty is unimportant because the prodUct of testzonevolume and test-zone compressibility (whichincludes test-zone volume in the denominator; seeEq. 6-9) affects pressure responses in a test zone, andthe volume terms cancel as the product is taken.6.4.2 COMPENSATION FOR CHANGES IN TEST·ZONE VOLUME. The volume of a test zone does notremain constant throughout a permeability-testingsequence. Creep closure of a borehole could causethe test-zone volume to decrease. The radial LVDTson the test tools were designed to measure boreholeclosure directly. Unfortunately, forthe tests discussedin this report, the data from the radial LVDTs areconsidered unreliable (soe Section 0.2of Appendix D).The potential closure of a typical borehole wascalculated and found to have an insignificant effect ontest-zone volume on thE~ time scale of the tests (seeSection D.60f Appendix 0). Accordingly,creepclosurewas not included in the test-zone volumecompensations used forthe test simulationspresentedin this report. As reliable radial-LVDT data becomeavailable for future tes.ts, however, the measuredborehole-radius changes will be incorporated directlyinto the test-zone-volume compensations.The volu me of a test zone can also change in responseto changes in the fluid pressure within the test zone.Fluid-pressure changes in the test zone can cause:1) changes in the volumes of the non-packercomponents of the test-tool; 2) borehole-radiuschanges; and 3) test-zone volume changes due toaxial test-tool movement. The net effect of these threechanges can be combined to give the total change intest-zone volume (IlV ) tzas follows:where:IIV1001(t)IIVrad(t) ==test-tool-volume change at time tborehole-radius-volume change attime tII Vax(t) == test-tool-volume change due to axialtest-tool movement at time tAs discussed in Section 0-1 of Appendix 0, the threeterms of Eq. 6-5 can be expressed as:llVtoom C tOOIP(t)(6-6)IIVrad(t) == C rad P(t)(6-7)IIVax(t) Cax [Lax(t) - Lax(O)](6-8)where:C IoOItest-tool volume constantC rad borehole-radius volume constantCax == axial test-tool-movementvolume constantP(t) test-zone pressure at time tLax(O) initial axial LVDT measurementLax(t) == axial LVDT measurement at time tThe volume constant Cax includes the test-zone andtest-tool-specific constants for borehole radius, testzone-packerend-sub radius, and the radius of theaxial-LVDT actuator rod. The borehole radius isassumed to be constantforthe calculation of Cax' Theminor changes in radius determined from Eq. 0-9were determined to have negligible influence on thecalculated volume change IIVax'42


Table 6-3Test-Zone Compressibilities Calculated from Fluid Volumes Measured During Pulse WithdrawalsTest-Zone Pressure Test-ZoneTest-Zone Test-Zone Test-Tool Fluid Before Pressure Volume Volume CalculatedLength Radius Volume Volume Pulse After Pulse Removed Change Compress. Free GasTest ID (cm) (cm) (cm 3 ) (cm 3 ) (MPa) (MPa) (cm 3 ) (cm 3 ) (1/Pa) Observed?C2H01-B-PW2 108 5.200 3526 5648 2.836 0.783 14.0 N.C. 1.21 x 10- 9 NoC2H01-C-PW1 234 5.226 15037 5040 7.563 4.232 50.0 8.1 2.50 x 10- 9 NoC2H01-C-PW2 234 5.226 15037 5040 7.709 4.179 71.0 6.2 3.64 x 10- 9 1 second onlyC2H02-PW2 139 5.185 8528 3212 8.442 5.226 110.0 3.0 1.05 x 10- 8 No~c.vC2H02-PW3 139 5.185 8528 3212 8.492 6.123 72.0 2.2 9.28 x 10- 9 NoL4P51-A-PW1 142 5.297 8513 4004 2.082 1.045 5.0 2.1 7.01 x 10- 10 NoL4P51-A-PW2 142 5.297 8513 4004 2.180 1.080 5.5 2.3 7.31 x 10. 10 No80P01-PW1 143 5.175 8511 3520 2.330 1.543 42.0 1.3 1.47 x 10- 8 Yes80P01-PW2 143 5.175 8511 3520 2.760 1.449 92.0 1.4 1.96 x 10- 8 Yes80P01 GZ-PW1 105 5.175 6566 2268 0.463 0.226 7.3 N.C. 1.36 x 10- 8 Yes81 P71-A-PW1 144 5.211 8542 3742 1.602 0.868 80.0 0.7 2.89 x 10. 8 No81 P71-A-PW2 144 5.211 8542 3742 1.565 0.784 156.0 0.7 5.31 x 10- 8 NoNote: No axial data for C2H01-B, C2H02, 81 P71-A, and all GZFor comparison: Compressibility of NaCI-saturated brine: 3.1 x 10- 10 Pa- 1


Eqs. 6-5 through 6-8 were applied to the test-zonepressureand axial-LVDT data recorded during thetests. Fortestswhere axial-LVDTdatawere unavailableor unreliable, the ~Vax(t) term was not included. The~VIZ-versus-time data were then used to determine afunctional representation of the data which wasincorporated directly into the test-interpretationsimulations. The methods used to incorporate thesedata in the simulations include both the effect of testzonevolume on the pulse-test boundary condition,and the effect of induced flow rates due to changes intest-zone volume versus time.6.5 Test-Zone CompressibilityTest-zone compressibility is an important factor inpermeabilitytesting performed undershut-in conditionsbecause, given the volume of a test zone, the test-zonecompressibility governs the amount of fluid that mustflow into or out of the test zone to create a givenpressure change. In an ideal system, characterized bya pressure-invarianttest-zone volume completely filledwith a homogeneousfluid, the test-zone compressibilitywould be equal to that of the test-zone fluid. However,the fluid-pressure responses observed during pulsewithdrawals indicatethat thetest-zone compressibilitiesin the permeability-testing program were considerablygreater than the compressibility of the test-zone brinealone.Neuzil (1982) observed test-zone compressibilities afactor of six larger than water compressibility duringpressure-pulse testing ofthe Pierre Shale. He evaluatedthe possible factors that could be responsible for theapparently high test-zone compressibilities, andconcluded that test-tool compliance and air entrapmentwere probably most important. He also emphasizedthe importance ofmeasuring test-zone compressibilityrather than simply assuming that it would be equal tofluid compressibility, because of the proportionalitybetween test-zone compressibility and interpretedhydraUlic conductivity. Hsieh et al. (1983) also reporttest-zone compressibilities higher by a factor of fivethan water compressibility and relate the highercompressibilities to test-tool compliance.Six factors were identified that could be contributing tohigh test-zone compressibilities in the Saladopermeability-testing program:1) non-packer test-tooI-component compressibility­The volumes of the various metal components ofthe test tool, specifically the transducer carriers,mandrels, and transducer and vent lines, vary inresponse to changes in test-zone fluid pressure.2) borehole compressibility - The radius of the boreholevaries in response to applied test-zone fluidpressure.3) axial test-tool movement - The test tool moves intoand out of the test boreholes in response toappliedtest-zone fluid pressure. The movement isparticularly noticeable during pulse withdrawalsand was observed during all tests conducted withtest tools equipped with axial LVDTs.4) test-zone-packer deformation - Both long-termand short-term variations in the test-zone-packerinflation pressure were observed in all of thepermeability tests. Assuming that the packer andthe associated packer-inflation tubing form a closedsystem and that pressure changes are not due tofluid leakage, then the changes in packer-inflationpressure imply a concomitant change in the internalvolume of the packer system. The assumptioncan then be made that the external volume of thepacker system is varying, which in turn implies atime-varying impact on the test-zone volume.44


5) entrappedlcreated gas in the test-zone - Gas wasobserved during the venting of the test zones forsome of the pulse-withdrawal tests. Fourpotentialgas sources have been identified: airentrapped inthe test zone during test-tool installation; gascreated as a result of the reaction of the metal toolcomponents withthe test-zone brine; gas exsolvedfrom the formation fluid; and gas created throughanaerobic bacterial degradation of hydrocarbonsthat might be contaminating the test zone.The test-zone gas may be eitherfully dissolved inthe test-zone fluid, exsolving during the suddenpressure drop caused by zone venting, orthe gasmay occur as a separate phase at testing pressures.A substantial increase in test-zone compressibilitywould be expected if the gas werepresent as a separate phase.6) creep closure of the borehole - Halite and argillaceoushalite undergo plastic steady-state creep inunderground openings (Krieg, 1984; VanSambeek, 1987). Therefore, the potential existsfor borehole volume to change due to creep closureof the boreholes during permeability testing.respect to pressure. However, the bulk effect of thesetwo factors over specific pressure ranges, as well asany other unaddressed factors, can be estimatedusing the compressibility equation and data collectedwhen venting the test zones to start pulse-withdrawaltests.Zone-compressibility values for some individual testanalyses were calculated using the brine volumesremoved from the test or guard zones during pulsewithdrawals and the test- or guard-zone fluid pressuresobserved immediately before and immediatelyafter the withdrawals. In the case of the tests inborehole SOP01 , volumes of gas that were producedalong with brine during the pulse withdrawals were notmeasured, and were not, therefore, included in thetest-zone-compressibility calculations. Volume compensationas described in Section 6.4.2 was includedin these calculations. The test-zone compressibilitywas calculated usingthe following form ofthe equationfor fluid compressibility:(6-9)Appendix 0 presents a thorough discussion of thesewhere:six factors, and, where possible, quantifiestheirpotentialimpacts onthe observed fluid-pressure responses.All of these factors except for the last one, creepclosure, could have a significant potential impact ontest-zone compressibility. Creep closure occurs tooslowly to affect test-zone compressibility.CtzVtz(O)V wVaPi==test-zone compressibilityinitial test-zone volumevolume of brine withdrawncompensated volumetest-zone pressure before the pulsewithdrawaltest-zone pressure after the pulsewithdrawalThe effects of the first three factors listed above areincorporated in the model simulations as discussed inSection 6.4.2. The impact of factors 4) and 5), testzone-packerdeformation and test-zone gas, are impossibleto quantify separately at this time. The effectsof both factors are expected to be nonlinear withThe compensated volume term in Eq. 6-9 is requiredto accountforchanges in the test-zone volume causedby the pressure change during the pulse. Thesechanges would not otherwise be included in the simulationsbecause the actual pulse is a discontinuity thatis not simulated. Va for each pulse withdrawal was the45


difference in test-zone volumes (Vtz(t)) immediatelybefore and after the pulse, calculated using Eq. 6-5 asdescribed in Section 6.4.2.(Table 6-3). In addition, packer-inflation pressureswere more stable after implementing these procedures(Saulnier et aI., 1991).Equation 6-9 does not take into account variation intest-zone compressibility as a function of pressure.However, the equation can be viewed as representingthe average test-zone compressibility over the particularpressurerange used in the calculation, which is alsothe pressure range of interest in the test interpretations.Use of this equation to calculate test-zonecompressibility should not, therefore, result in significanterror in the test interpretations. The Ctz valuesused in the test interpretations presented in this reportcan be found in Table 6-3 along with the measuredfluid volumes removed during pulse withdrawals, theobserved pressures, and the volume compensationsused. The calculated volume compensations wereinsignificant in the calculation of test-zone compressibilities,being less than 0.2% of the test-zone volumein all cases. The calculatedtest-zone compressibilitiesranged from 7.01 x 10-'0 Pa-' to 5.31 x 10. 8 Pa' l , ascompared to the compressibility of the test-zone fluid,which was approximately 3.1 x 10- 10 Pa- 1 . These highvalues of test-zone compressibility reflect the importanceof the factors that could not be independentlyquantified, packer deformation and test-zone gas.As mentioned in Appendix D, a number of modificationshave been made to the multipacker test tools,test-tool materials, and test-tool installation proceduresto help minimize the impact of packer deformationand entrapped gas on test-zone compressibility.The test-zone compressibilities calculated from pulsewithdrawaltests in L4P51 , which were performed aftermodifying test procedures and test-tool materials, wereone-half order of magnitude lower than those calculatedfrom the pulse-withdrawal tests performed inother boreholes before these changes were enactedWhen more than one test-zone-compressibility valuewas calculated for a sequence of tests, as in tests inborehole S1 P71-A, a log-average value of Ctz wasused in the interpretations. The calculated Cll valuesused in the test interpretations do not incorporatepotential non-linearities and time-varying behaviorthatmay have occurred.6.6 Thermal EffectsAnalysis of permeability tests in low-permeability mediahave shown that the thermal expansion orcontractionof the test-zone fluid can produce significant f1uidpressureresponses in isolated test zones (Pickens etaI., 1987). Changes in test-zone-f1uid temperaturemust be included in test analysis to account for f1uidpressurechanges due to the thermal expansion of thetest-zone fluid. GTFM accounts for the influence oftest-zone temperature changes in test analyses. Observedfluctuations in test-zone and packer-inflationpressures were apparently due in part to the temperaturechanges. Assuming that the in situ formationtemperature is constant, the source of the observedtemperature variations appears to be changes in theambient air temperature in the rooms and drifts, whichwere communicated to the boreholes through themetallic cores of the test tools.Thermocouples were used to monitor test-zone andguard-zone temperatures during permeability testing.The analysis model was used to create a functionalrepresentation of the temperature-versus-time data,which was then incorporated directly into the testinterpretationsimulations as a wellbore flux equal tothe calculated fluid expansion or contraction.46


7. ESTIMATION OF HYDRAULIC PROPERTIESThis chapter presents individual interpretations of thepressure-pulse tests conducted in the boreholes discussedin Chapter 5. The interpretations given inSection 7.1 include GTFM simulations of the tests andestimates of the hydraulic parameters of the testedintervals. Section 7.2 presents sensitivity analyses ofthe interpreted results and addresses the quantitativeeffects of hydraulic- and material-property uncertaintieson the interpreted hydraulic parameters. Section7.3 summarizes the overall uncertainties in the testinterpretations.7.1 Individual Test InterpretationsThe tests performed in the individual boreholes arediscussed and interpreted below. The fluid-pressureresponses observed in the guard zones during thetesting in the test zones are also examined to see if anyconclusions can be drawn about the hydraulic propertiesof the guard-zone intervals. A summary of theinterpreted results is presented in Table 7-1.7.1.1 C2H01-A. Borehole C2H01 was the first boreholedrilled for the Salado permeability-testing program(see Section 5.1). As described in Chapter 3, theC2H01-A testing was performed with the multipackertest tool used in the waste-handling shaft. which hasneither radial nor axial LVOTs (see Figure 3-1). Figure7-1 shows the configuration of the test tool inC2H01 for the C2H01-A testing, and indicates thelengths and stratigraphic locations of the guard andtest zones. The guard zone for the C2H01-A testingextended from about 0.50 to 1.64 m below the floor ofRoom C2 and included the lower part of map unit 7(argillaceous halite) and most of map unit 6 (halite).The test zone extended from about 2.09 to 5.58 mbelow the floor of the room and included most of mapunit 5 (argillaceous halite), all of map units 4 (argillaceoushalite), 3 (halite), and 1 (polyhalitic halite), anda portion of map unit 0 (argillaceous halite). Map unit2 was not recognizable in C2H01.The C2H01-A testing consisted of a shut-in periodfollowed by two pulse-injection tests. The fluid-pressureresponses to th.e pulse injections were so rapidthat the test period was terminated earlier than normalso thatthetesttool could be removed from the hole andtested for leaks. Leak testing revealed no problemswith the tool and, therefore, the fluid-pressure responsesobserved during testing are believed to berepresentative of the formation tested. The fluidpressuredata from the test and guard zones during theC2H01-A testing are shown in Figure 7-2.7.1.1.1 Test Zone. As described in Saulnieret al. (1991), the C2H01-A testing period was precededby a 21-day period during which the boreholewas at ornearatmospheric pressure. The multipackertest tool was first installed immediately after drillingwith a length of 10.16-cm (4-inch) 0.0. seamless pipefixed to the end of the tool to reduce the fluid volume ofthe test zone. Because of a leak in the volumereductiondevice, no fluid-pressure buildUp was observedin the test zone after the test zone was shut in.This period, which included attempts to increase thetest- and guard-zone pressures by injection, was includedin the test analysis as a specified-pressureborehole-history sequence.The multipacker test tool was removed from the holeand reinstalled without the volume-reduction deviceon August 24, 1988 (Calendar Day 237). The test andguard zones were shut in on August 25 (Calendar Day238). and testing began later that same day. Thetesting consisted of two pUlse-injection tests. The firsttest lasted about five days, and the second test lastedabout two days (Figure 7-2).47


Table 7-1Test-Interpretation ResultsFormationSimulated Hydraulic Hydraulic Pore Radius ofTest Test Interval Hole Lithology Thickness Conductivity Permeability Diffusivity Pressure Influence(m) Orientation (map unit) (m) (m/s) (ni) (m 2 /s) (MPa) (m)aC2H01-A 2.09 - 5.58 vertical argo halitedown (0-5) 3.49 5.2 x 10- 12 7 x 10- 19 5.5 X 10- 5 0.48 6/15(4-5) 0.83 2.0 x 10- 11 3 X 10- 18 2.1 X 10- 4 0.50 10/35C2H01-B 4.50 - 5.58 vertical argo halite 1.08 3.9 x 10- 14 5 X 10- 21 4.1 X 10- 7 3.15 2/6down (0)C2H01-B-GZ 2.92 - 4.02 vertical argo halite 1.10 1.4 x 10- 14 2 X 10- 21 1.5 X 10- 7 4.12 1/4down (0-4)C2H01-C 6.63 - 8.97 vertical anhydrite 0.96 7.0 x 10- 12 1 X 10- 18 5.0 X 10- 5 8.05 5/35~down (MB139)(XlC2H02 9.47 - 10.86 45° down anhydrite 0.88 5.7 x 10- 13 8 X 10- 20 4.1 X 10- 6 9.30 5/20(MB139)C2H03 7.76 - 9.14 horizontal pure halite 1.38 < 1O- 14 ? < 10- 21 ? ? ? ?(9)L4P51-A 3.33 - 4.75 vertical argo halite 1.42 4.5 x 10- 14 6 X 10- 21 3.5 X 10- 7 2.75 2.0 bdown & clay DSOP01 3.74-5.17 vertical argo halite 1.43 6.1 x 10- 14 8 X 10- 21 5.5 X 10- 7 4.45 2/8down & clay DSOP01-GZ 1.86 - 2.91 vertical anhydrite 0.90 < 4.2 x 10- 11 ? < 6 x 10- 18 ?


BOREHOLE: C2HOlTOOL: #1DATE: 08/05/88DEPTH OF HOLE: 5.575 m.BOREHOLESTRATIGRAPHY0.00 ~·~-'---~~M~A~P~U~N~I=T~7=----~---------I- COARSE, ARGILLACEOUS HALITEGUARD-ZONEPACKER -MAP UNIT 6- MEDIUM TO FINE ORANGE HALITEwzoNIo0::«::::JClGUARD-ZONElTRANSDUCERPORT-1.64*--- COARSE, COLORLESS HALITE2.09*--MAP UNIT 5- COARSE, ARGILLACEOUS HALITETEST-ZONETRANSDUCER~ PORT---·olloNIt-If)Wt-MAP UNIT 4- MEDIUM TO FINE ARGILLACEOUSHALITEMAP UNITS 3 & 1- COARSE, ORANGE POLYHALITICHALITEMAP UNIT a- MEDIUM TO COARSE ARGILLA­CEOUS HALITE, CLAY DECREA­SES DOWNSECTION, POLYHALITEX INCREASES DOWNSECTION459 ~·~-l------~-+-----CLAYPARTING ~-----~488 ~XCLAY PARTING ~-----~5. 58 ~.~..L-.~_---.JFigure 7·1. Configuration of Multipacker Test Tool #1 In Borehole C2H01 for C2H01·A Testing.49


-0- Test Zone-0- Guard Zone3.5Test C2H01-A, Room C22.5 Test Zone 2.09 - 5.58 m, Vertically DownArgillaceous Halite, Map Units 0, 1, 2, 3, 4, and 51.50.5-0. 5 ~--&,-,-"""--..L....J""""-'--'-...L-.......--,--,-",,,,--..L....J""""-'-....L...""""''''''''--'--'-''''''''''''''''''''''''''--&.-'-'''''''''''''''''--'215 220 225 230235240 245250Time (1988 Calendar Days)TRI-6344-561-0Figure 7·2. Test· and Guard·Zone Fluid-Pressure Data from C2H01-A Testing.Figure 7-2 shows that the test-zone fluid pressureresponded very rapidly immediately after the pulseinjections were shut in, recovering from a significantfraction of each induced pulse in a period of minuteswhile the remainder of the recovery occurred over aperiod of days. This early-time response is too rapid tobe representative of the true formation response.Similar rapid partial recoveries from pulse injectionsand withdrawals have also been observed duringcompliance testing in steel casing (Saulnier et aI.,1991) and during the other tests discussed in thisreport. These rapid recoveries are therefore believedto beprimarily related to tool-compliance effects. Someportion ofthe early-time response might also reflect thepresence of a damaged zone, or skin, around theborehole with permeability and porosity increasedrelative to that of the undamaged formation. Thisdamage could be caused by dilation ofthe rock aroundthe borehole immediately after drilling. Whether theearly-time response observed during testing is relatedto tool compliance, a skin around the borehole, orboth,it is not considered to reflect the properties of theformation outside of the hypothesized skin. Therefore,the post-pu Ise early-time pressure responses observedduring all testing discussed in this report were treatedas periods of specified pressure in the simulations.The effects of this treatment on interpretation of formationproperties are discussed in Section 7.1.2.1.Figure 7-3 shows the best-fit model simulation of theC2H01-A pulse-injection tests along with the observedfluid-pressure data from the test zone. Comparedto all other tests, much larger percentages ofthe C2H01-A post-pulse pressure responses had tobe included as specified-pressure history periods toobtain any reasonable agreement between the simulationsand the observed data. Even so, the matchbetween the simulation and the observed data is notas good as might be hoped, particularly for the firstpulse test. All modifications made to the fittedparameters to improve the fit to the first pulse test,however, had the effect of degrading the fit to the50


3.5(I 0 Data I -- Simulation((i;"" 2.50-~Q)...~...(/)(/)Q)0-1.50.5Test C2H01-A, Room C2Test Zone 2.09 - 5.58 m, Vertically DownArgillaceous Halite, Map Units 0, 1,2,3,4, and 5HistoryK = 5.2 x 10- 12 mls (k =7 x 10- 19 m 2 ) - ~-Ss = 9.5 x 10- 8 m- l - r--p' = 0.48 MPaC tz= 1.21 x 10- 9 Pa- l "~\> ~History~0""History ..r-- Simulation ..I-0.5o 5 10 15 20 25 30to = 1988 217.5464Time Since Hole Cored (days)TRI-6344-562-0Figure 7-3.Best-Fit Model Simulation of the Test-Zone Fluid-Pressure Response During C2H01-ATesting.second pulse test. The specified parameters for thesimulation were a formation thickness of 3.49 m, aspecific storage of 9.5 x 10- 8 m-l, and a test-zonecompressibility of 1.21 x 10- 9 Pa- 1 • The test-zonecompressibility value used was determined duringthe C2H01-B testing (see Section 7.1.2.1) becauseno data were provided by the C2H01-A testing thatwould allow calculation of that parameter. The fittedparameters for the simulation shown in Figure 7-3were a hydraulic conductivity of 5.2 x 10- 12 m/s(permeability of 7 x 10- 19 m 2 ) and a formation porepressure of 0.48 MPa. Additional simulations showingthe sensitivity of the best-fit model to slightchanges in hydraulic conductivity, formation porepressure, specific storage, and test-zone compressibility,as well as to the presence or absence of testzone-volumecompensations, are presented in Section7.2.The well-test-analysis model was used to examinethe radius of influence of the C2H01-A testing.Figure 7-4 shows the simulated pressure responseat different radial distances from the boreholethroughout the entire C2H01-A testing period. Thelongest duration, highest magnitude response wascaused by the initial 21-day period during which thehole was depressurized. The simulated effects ofthis depressurization had propagated to a distanceof more than 15 m from the hole by the end of themonitoring period. The effects ofthe individual pulsetests can be seen to a distance of about 6 m from thehole. That is, the slopes of the pressure CUNes outto 6-m distance change visibly after each pressurepulse in the test zone. In the case of the 6-mpressure curve, these changes in slope occur aboutone day after the pulses.51


0.700.650.60C?0.55Cl.0.50::2-Q) .... 0.45:::l(/)(/)Q) 0.40....Cl.0.350.300.25--a- R = 15.0 m-e- R= 6.0m-A- R= 3.0 m-+- R= 1.5m-*- R= 0.5m0.200 5to. 1988217.546410 15 20Time Since Hole Cored (days)25 30TRI-6344-563-0Figure 7-4.Simulated Formation Pore Pressures at Selected Radial Distances from the Test ZoneDuring C2H01-A Testing.During the C2H01-B tests, which followed the C2H01­A tests, most of the C2H01-A test zone was containedin eitherthe C2H01-B guard zone ortest zone. Excludingthe interval covered by the C2H01-B test-zonepacker, only the portion of the C2H01-A test zone from2.09 to 2.92 m below the floor of Room C2 was notincluded in eitherthe C2H01-B guard ortestzone. Theresponses observed in the C2H01-B test and guardzones during testing were qualitatively different fromthe responses observed during the C2H01-A testing,with lower interpreted hydraulic conductivities andhigher interpreted formation pore pressures (see Section7.1.2).ThebehaviorobservedduringtheC2H01-Atesting may, therefore, largely reflect the hydraulicproperties of only the upper 0.83 m (or less) of the testzone.The C2H01-Atests were resimulated assuming a testzonethickness of 0.83 m. Figure 7-5 shows the matchbetween the observed data and the best simulationobtained. The simulation matches the observed datano betterthan did the simulation usingthe full test-zonethickness (Figure 7-3). The specified parameters forthe simulation were a formation thickness of 0.83 m, aspecific storage of 9.5 x 10- 8 m-1, and a test-zonecompressibility of 1.21 x 10- 9 Pa- l • The fitted parameterswere a hydraulic conductivity of 2.0 x 10- 11 mls(permeability of 3 x 10- 18 m 2 ) and a formation porepressure of 0.50 MPa. Using these properties, theradius of influence of the entire testing period wasabout 35 m, while the effects of each pulse could beobserved to a distance of about 10 mfromthe borehole(Figure 7-6).In summary, the interpretation of the C2H01-A testsis uncertain. The portion of the test zone thatactually contributed to the observed responses cannotbe determined, and none of the simulationsmatched the observed data satisfactorily. However,later testing in both borehole C2H01 and other52


4.53.5I 0 Data I- Simulation"@'a...::2-Q)'-::lCJ)CJ)Q)'-a...2.51.50.5~-Test C2H01-A, Room C2Simulated Test Zone 2.09 - 2.92 m, Vertically DownArgillaceous Halite, Map Units 4 and 5pHistoryK = 2.0x10-11m/s(k=3x10-1Sm2)S. = 9.5 x 10- S m- 1 -< ~-- f--p' = 0.50 MPaC = 1.21 x 10- 9 Pa- 1 tz~ ~--~.... ""(~History _History -1-Simulation--0.5o 5 10 15 20 25 30to - 1985 217.5464Time Since Hole Cored (days)TRI-6344-564-0Figure 7-5.Best-Fit Model Simulation of the Test-Zone Fluid-Pressure Response During C2H01-ATesting, Assuming a Simulation Thickness of 0.83 m.Note: Simulation Thickness is 0.83 m0.6"@'a...0.56Q)'- ::lCJ)CJ)Q)"-a.0.40.3-&-R=35m-e- R=20m-6-R=10m-.- R= 3m-*- R= 1mto = 1988 217.5464Time Since Hole Cored (days)TRI-6344-565-0Figure 7-6.Simulated Formation Pore Pressures at Selected Radial Distances from the Test ZoneDuring C2H01-A Testing, Assuming a Simulation Thickness of 0.83 m.53


holes, discussed below, has provided additionalinsight into the C2H01-A test responses. Furtherdiscussion of the C2H01-A tests is deferred, therefore,to Section 7.3.1.7.1.1.2 Guard Zone. No pressure buildupwas observed in the guard zone during the C2H01-Atesting (Figure 7-2). The guard zone may have beenconnected to the atmospheric pressure in Room C2through fractures in the rock near the excavation.Borns and Stormont (1988) report the development ofa disturbed rock zone (DRZ) within one to two metersof the WI PP excavations. This DRZ is characterizedby fracturing and an increase in permeability (seeSection 7.3.1). Considering that Room C2 was morethan four years old at the time of the C2H01-A testing,some fracturing in the floor was to be expected.7.1.2 C2H01-B. After the C2H01-A testing wascompleted, the multipacker test tool was removedfrom the hole, tested for leaks, and reinstalled at agreater depth in the hole for the C2H01-B testing.The configuration of the test tool in the borehole forthe C2H01-Btesting is shown in Figure 7-7. The testzone extended from 4.50 to 5.58 m below the floor ofRoom C2, and was contained entirely within mapunit 0 (argillaceous halite). The guard zone extendedfrom 2.92 to 4.02 m below the floor of theroom, and included all of map units 3 (halite) and 1(polyhalitic halite), and portions of map units 4 (argillaceoushalite) and 0 (argillaceous halite). Thus, thetest and guard zones for the C2H01-B testing isolateddifferent portions of what had been the testzone for the C2H01-A testing (compare Figures 7-1and 7-7).Figure 7-8 is a plot of the test- and guard-zone fluidpressuredata collected by the DAS during the C2H01-Aand C2H01-B monitoring periods. The C2H01-B testingsequence consisted of an initial buildup period, followed bya pulse injection to increase the test-zone pressure andbring itclosertotheforrnationpore pressure, and two pulsewithdrawaltests in the test zone (Figure 7-8). Interpretationsofthe tests performed in thetest zone, aswell asofthefluid-pressure responses observed in the guard zone, arediscussed below.7.1.2.1 Test Zone. The multipacker test toolwas reinstalled in borehole C2H01 on September 1,1988 (Calendar Day 245) forthe C2H01-Btesting. Thetest and guard zones were shut in the next day. Thefluid-pressure buildup in the test zone was monitoreduntil September 28 (Calendar Day 272). The test zonefor the C2H01-B testing was subjected to the entireborehole-pressure history leading up to and includingthe C2H01-A testing. Therefore, the fluid-pressuredata collected by the DAS from the time the hole wasdrilled until the end of the C2H01-B buildup periodwere used to specify the test-zone pressure during theperiod preceding the pulse tests.Figure 7-8 shows that the fluid-pressure buildupafter shut in for the C2H01-B testing on CalendarDay 246 was not characteristic of a typical shut-inbuildup as shown on Figure 4-6. The ideal buildupresponse shown on Figure 4-6 is representative ofan incompressible test interval containing a constantcompressibilityfluid recovering from an episode ofdepressurization. The slope of the buildup curvecontinually decreases as the pressure differentialbetween the test interval and the surroundingformation decreases. In contrast, Figure 7-8 showsa buildup curve whose slope increases with time.This type of response could be caused by a testzonecompressibility that decreased with increasingpressure. As long as the test-zone compressibilitywas decreasing faster than the pressure differentialbetween the test interval and the surroundingformation, the slope of the pressure-buildup curvecould increase. As discussed in Section 6.5, the54


C2H01-BTEST-TOOL CONFIGURATIONBOREHOLE: C2HO 1TOOL: #1DATE: 09/01/88DEPTH OF HOLE: 5.575 m.EXTENSION_~_--==B=O~R=EH=O=L=E=S=T==R=AT=I=G=RA=P=H=Y=-1.96 --+----+--M-A-P-U-N-I-T-5----------I- COARSE. ARGILLACEOUS HALITE---I000 - MAP UNIT 7- COARSE. ARGILLACEOUS HALITE0.68 --+=----l--M~A~P~U':;.;N.;;,IT~6


4.5 ,.....-r-r-.,........--r-r-................,...,.-r-..,....,--r-.-,....,.........,......,-r-...,....,...........,....,.-r-,......,--.--.-..,..........,...,....,...,3.5rna..2.5~0.5Test C2H01-B, Room C2Test Zone 4.50 - 5.58 m, Vertically DownArgillaceous Halite, Map Units 0-0.5 -.L.. ...L.. ...a- -.L.. ..........210235260285310335Time (1988 Calendar days)360385410TRI-6344-566-0Figure 7-8.Test· and Guard·Zone Fluid-Pressure Data from C2H01-B Testing.combination of test-tool compliance, packerdeformation, and/orgas in the test zone could causethe compressibility of the test zone to have a nonlineardependence on pressure.Figure 7-9 shows the best-fit model simulation of theC2H01-B testing period compared to the observedfluid-pressure data. As noted on the figure, the timefrom the drilling of the test zone to the pulse injectionwas included as specified-pressure history. Thespecified parameters used in the simulation of thepulse-injection and two pUlse-withdrawal tests werea formation thickness of 1.08 m, a specific storageof 9.5 x 10- 8 m\ and a test-zone compressibility of1.21 x 10- 9 Pa- 1 • The fitted parameters were ahydraulic conductivity of3.9 x 10- 14 mls (permeabilityof 5 x 10- 21 m 2 ) and a formation pore pressure of3.15 MPa. Additional simulations showing the sensitivityof the best-fit model to slight changes inhydraulic conductivity, formation pore pressure, andspecific storage, as well as to the presence orabsence of test-zone-volume compensations, arepresented in Section 7.2.Figure 7-8 shows that the test-zone fluid pressureresponded very rapidly immediately after the pulseinjection and two pulse withdrawals were shut in,recovering from a significant fraction of each inducedpulse in a period of minutes while the remainder of therecovery took weeks. As discussed in Section 7.1.1.1,these early-time responses are believed to be primarilyrelated to tool-compliance effects. Thus, a portion ofthe early-time response observed during testing wastreated as a specified-pressure history in thesimulations. Figures 7-10 through 7-12 show the datafrom the three C2H01-B pulse tests with simulationsperformed including and not including an early-timespecified-pressure history, using the hydraulicparameters defined forthe best-fit simulation shown inFigure 7-9. In all cases, the simulation including anearly specified-pressure history fits the complete dataset better than the simulation with no history. The56


54History {K = 3.9 X 10. 14 mls (k = 5 X 10. 21 m 2 )Ss = 9.5 X 10. 8 m- 1p' = 3.15 MPaC tz= 1.21 X 10. 9 Pa- 1oData- Simulationcu 3Cl.::2Q)2 '- ::J


'@' 2.5a.:!:Q)....::::lCJ)CJ)Q)....a.2.0oData- Simulation with Initial History Period- - . Simulation without Initial History PeriodX Initial Historyto - 1988 217.546685 95 105 115 125 135Time Since Hole Cored (days)TRI-6344-569-0Figure 7-11.Best-Fit Model Simulation of Pulse-Withdrawal #1 During C2H01-B Testing Showingthe Effect of an Initial Fluid-Pressure History Period.3.2 .......--r...........-,.......,...............-.-,.......,..........,...-.-,.....,..........,..........,.....,..........,....................--r....-...r-r--r.......-,cu a. 2.2:::i!:-Q)....::::lCJ)CJ)Q)....a.2.7 ---1.71.2-0- Data- Simulation with Initial History Period- - Simulation without Initial History Period-0- Initial History0.7 .............................1-........-'--..............................1-........-'--........--1.--1............1-......................--1.--1............1-......................--1.......130to - 1988217.5466140150160 170Time Since Hole Cored (days)180 190 200TRI-6344-570-0Figure 7-12.Best-Fit Model Simulation of Pulse-Withdrawal #2 During C2H01-B Testing Showingthe Effect of an Initial Fluid-Pressure History Period.58


simulation lacking an early specified-pressure historyinvariably shows an early-time recovery less rapidthan that actually observed, in keeping with the timescales of actual formation responses. Significantly,however, the pairs of simulations become increasinglysimilar with time, showing the overriding influence ofthe formation-parameter estimates on the late-timepressure behavior. Thus, questions about the exactdelineation of the period that should appropriately beincluded as history are moot.The well-test-analysis model was used to examinethe radius of influence of the C2H01-B testing.Figure 7-13 shows the simulated formation-fluidpressures at different radial distances from the boreholethroughout the entire C2H01-B testing period.The longest duration, highest magnitude responsewas caused by the initial 55-day period during whichthe hole was either completely depressurized or atrelatively low pressure « 1 MPal. The effects of thisdepressurization had propagated to a distance ofabout 6 m from the hole by the end of the monitoringperiod. The effects of the individual pulse tests canbe seen to a distance of about 2 m from the hole.That is, the slopes of the simulated pressure curvesout to 2-m distance change visibly after each pressurepulse in the test zone. In the case of the 2-mpressure curve, these changes in slope occur 10 to15 days after the pulses.7.1.2.2 Guard Zone. Although no testing wasspecifically performed in the guard zone during theC2H01-B testing, tool compliance transmitted a portionof each test-zone pulse to the guard zone (Figure7-8). The two pulse withdrawals in the test zone,in particular, produced responses in the guard zonethat could be used to estimate formation hydraulicparameters.Figure 7-14 shows the best-fit model simulation of theC2H01-B guard-zone response compared to the observedfluid-pressure data. As noted on the figure, thetime from the drilling of the guard zone to the first pulsewithdrawal in the test zone was included as specifiedpressurehistory. Brief specified-pressure history segmentswere also used at the start of each pulserecovery. Because the pressure pulses in the guardzone were created by tool responses to pressurechanges in the test zone, the pressure buildups followingthe pulses were probably also caused, in part, bytool compliance. Specifically, recovery to the prepulsepressure could be due entirely totool complianceif the test-zone pressure were recovering to its prepulsevalue over the same time period. Increases inthe guard-zone pressure beyond the pre-pulse pressure,particularly if the test-zone pressure was stillbelow its pre-pulse value, must reflect formation response.Thus, the response observed in the guardzone during the first "pulse test" shown on Figure 7-14probably includes a greater component of formationresponse than does the response during the second"pulse test." This conclusion appears to be borne outby the simulation shown on Figure 7-14, which matchesthe observed data well during the first pulse test, butfalls below the observed data during the second pulsetest.The specified parameters used to create the simulationof the two pulse-withdrawal tests shown on Figure7-14 were a formation thickness of 1.10 m, aspecific storage of 9.5 x 10- 8 m 1 , and a guard-zonecompressibility. Lacking any independent estimate ofthe guard-zone compressibility, the calculated compressibilityof the test zone (1.21 x 10- 9 Pa") was alsoused to approximate the guard-zone compressibility.The fitted parameters were a hydraulic conductivity of1.4 x 10- 14 mls (permeability of 2 x 10- 2 ' rn2) and a59


3.0'@'a..::2-Q)2.6~::::l(J)(J)Q)~a..2.2 -e- R =6.0m-e- R =3.5m-Ir- R=2.0 m-+- R= 1.0m-*"" R=0.5m1.8 ~"""""",-.&.....I""""-'-"""'''''''''''''''''~''''''''-L...'''''''''''''''''''''''...L-''''''''''''''''''''''.L....I''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''o2550'0 - 1988 217.5466 Time Since Hole Cored (days)75100125150175200TRI-6344-571-0Figure 7-13.Simulated Formation Pore Pressures at Selected Radial Distances from the Test ZoneDuring C2H01-B Testing.4.5 r-r........,...."T"'""r-t'-r-..,...."T"'""r-t'-r-..,....,....,r"""T-r-..,....,....,r"""T.........-,....,r"""T.........-,....,...............-...................."T"'""T"""13.52.5oData- SimulationTest C2H01-B GZ, Room C2Guard Zone 2.92 - 4.02 m, Vertically DownArgillaceous Halite, Map Units 0 - 4~::::l(J)(J)Q)~a..1.50.5K = 1.4Xl0-14mts(k=2x10·21m2)5 s = 9.5 X 10- 8 m- 1p' = 4.12MPaC gz = 1.21 X 10- 9 Pa- 11----- History----....1-------Simulation --------.~-0.5 ................""'-.................-'-........................~..........................................L-.......................L....I........-'-........."...............................-L..........................J25 50 75 100 125 150 175 200o10-1988217.4687 Time Since Hole Cored (days)TRI-6344-572-0Figure 7-14.Best-Fit Model Simulation of the Guard-Zone Fluid-Pressure Response DuringC2H01-B Testing.60


formation pore pressure of 4.12 MPa. Additionalsimulations showingthe sensitivity ofthe best-fit modelto slight changes in hydraulic conductivity, formationpore pressure, and specific storage, as well as to thepresence or absence of guard-zone-volume compensations,are presented in Section 7.2.The radius of influence of the C2H01-B guard-zone''testing'' was investigated by using the model to calculatepressure histories atdifferent radial distancesfromthe borehole. Figure 7-15 showsthatdepressurizationeffects extended to a distance of about 4 m during thetesting period. The effects of the individual pulse testscan be seen to a distance of about 1 m from the hole.7.1.3 C2H01·C. C2H01-C is the designation appliedto the testing in the deepened Mgment of boreholeC2H01. Borehole C2H01 was deepened from 5.58 to8.97 m belowthefloorof Room C2 on February 10 and11, 1989 (Calendar Days 41 and 42). The hole wasdeepened to allow testing of Marker Bed 139 in alocation where this unit was deeperthan 1 to 2 m belowan excavation. Figure 7-16 shows the configuration ofthetesttool in C2H01 during the C2H01-Ctesting, andindicates the lengths and stratigraphic locations of theguard and test zones. The test zone included MarkerBed 139 and halite and polyhalitic halite above andbelow the marker bed, while the guard zone includedargillaceous halite of map unit O.Figure 7-17 is a plot of the test- and guard-zone f1uidpressuredata collected during the testing period. Thetesting sequence consisted of an initial pressurebuildupperiod and two pulse-withdrawal tests in thetest zone. The C2H01-C testing period was precededby an initial5-day buildUp period as shown on Figure7-17. The multipacker test tool was removed from thehole afterthis short bUildup period and reconfigured toshorten the length of the test zone. On February 24,1989 (Calendar Day 55), the test zone was shut in to4.0Cii'c..3.5~~ ::J(/)(/)~c..3.02.5-e- R= 4.0m-e- R=2.0m-A- R= 1.0 m-+- R = 0.5 m~ R=0.3m2.0 L...I.-'-................L...............................L...o.-'-...............L.....I...-...........................-'-.............................L...I.~...............L.....I...-...........................~oto. 1999 217.4697255075100Time Since Hole Cored (days)125 150 175 200TRI-6344-573-0Figure 7-15.Simulated Formation Pore Pressures at Selected Radial Distances from the GuardZone During C2H01·B Testing.61


C2H01-CTEST-TOOL CONFIGURATIONBOREHOLE C2H01TEST TOOL #5DATE 02/23/89DEPTH OF HOLE 8966 mTOOLEXTENSIONGUARD-ZONEPACKER#304110 --Ib--.....J'--- 0 00 ---BOREHOLE STRATIGRAPHY. -------_._---------MAP UNIT 7- COARSE ARGILLACEOUS HA_L_IT~ _068MAP UNIT 6090 -1----1- - tv1EDIUM TO FINE ORANGE HALITE- COARSE, COLORLESS HALITE1.96 --258 -4.59 -_.MAP UNIT 5- COARSE ARGILLACEOUS HALITE- MAP UNIT 43 15 _.J=-=-+-------':'M:.::E:..:cD~1U::..cM~T'-=O'--..:..F~1N..'..'E=--:,A",R','G:,"IL::':L='-A"::'C-=E-=O-=U-=S H'--CAL='I~TE=--_.X X MAP UNITS .3 & 1X - COARSE, ORANGE POLYHALITIC HALITE3.84 -+-----J---=~='--'="-"-"."::'~'-':::'=-'-'~:.:..:..:.:::......:~c-'-'-'=---_IMAP UNIT 0-- CLAY PARTING ------~4.886.37- ..-----.-- CLAY PARTII~G ---------1-X _ MAP UNIT 0- MEDIUM TO COARSE ARGILLACEOUSHALITE, CLAY CONTENT DECREASESDOWNSECTION, POLYHALITE INCREASESXDOWNSECTIONx- XXX- XX POLYHALITIC HALITEX - COARSELY CRYSTALLINE HALITEX AND POLYHALITE6.80MARKER BED 139- 680-7_10 ANHYDRITE WITH MINORHALITE, 7.10-7_76 GRAY ANHYDRITE7.76""'" POLYHALITIC HALITELVDT # R-09X= - COARSELY CRYSTALLINE, ORANGE,w LVDT # . 8.211 BLEBS OF ORANGE ANHYDRITEz=XDECREASE DOWN SECTION0 LVDT #NIXI-UlWl-""'"XXX NOTE: MEASUREMENTS IN METERSTEST -ZONE FROM FLOOR BEFORE INFLATIONTRANSDUCER PORT*ESTIMATED POSITION AnERX8909 PACKER INFLATION.LVDT # A-01 -~ X_TD 8.966 897Figure 7-16.Configuration of Multipacker Test Tool #5 In Borehole C2H01 for C2H01-C Testing.62


9 ..................-T".,....,...,..,...,..........................""T""T'"T'""""T""T-r"'T...-....-.l"'T"""r"""I""'.......r""I""'l""T""...,...............-T""""".....-"T'"T..............,7TestC2H01-C. Room C2Test Zone 6.63 - 8.97 m. Vertically DownMarker Bed 1395060708090100110120-0- Test Zone-{]- Guard Zone-1 L.L.. ~ ...&...L. ..,&,..l L...l..I l....&..JL..L...l ............40Time (1989 Calendar Days)130140150TRI-6344·574-0Figure 7-17.Test- and Guard-Zone Fluid-Pressure Data from C2H01-C Testing.start the second buildup period, which continued untilthe test-zone-fluid pressure reached relative stabilityat 7.65 MPa in mid-March 1989.7.1.3.1 Test Zone. The pressure-buildupperiod in C2H01-C produced a non-characteristicbuildup curve (Figure 7-17) similartothat described forthe C2H01-B test zone in Section 7.1.2.1. The samefactors that could have led to a pressure-dependentcompressibility in that case might also have beenoperative in this case_ The test-zone compressibilitiescalculated for the two C2H01-C pulse withdrawals,2.50 X 10- 9 and 3.64 x 10- 9 Pa'1 (Table 6-3), are,however, higher than the test-zone compressibilitycalculated for C2H01-B, perhaps indicating a greateramount of gas in the C2H01-C test zone. A onesecondburst of gas from the test-zone vent line was infact observed during the second C2H01-C pulse withdrawal(Saulnier et aI., 1991).observed fluid-pressure data from the test zone. Thedata from the time of penetration of the center of thetest zone by drilling to the first pulse withdrawal wereincluded as specified-pressure history, as were thedata collected during the first minutes following thepulse withdrawals. The specified parameters used tosimulate the two pulse-withdrawal tests were aformation thickness of 0.96 m (corresponding only tothe Marker Bed 139 portion of the test interval) Ispecific storage of 1.4 x 10'7 m- 1 , and a test-zonecompressibility of 3.02 x 10- 9 Pa'1. The fitted parameterswere a hydraulic conductivity of 7.0 x 10- 12 mls(permeability of 1 x 10- 18 m 2 ) and a formation porepressure of 8.05 MPa. Addijional simulations showingthe sensitivity of the best-fit model to slight changes inhydraulicconductivity, formation pore pressu re, specificstorage, and test-zone compressibility, as well as tothe presence or absence of test-zone-volumecompensations, are presented in Section 7.2.aFigure 7-18 shows the best-fit model simulation of theC2H01-C pulse-withdrawal tests along with theThe well-test-analysis model was used to examinethe radius of influence of the C2H01-C testing.63


7oData- Simulationctl0..::2: 5-~:;:)


5-e- R=35m-&- R=20 m-A-R=10m-+- R= 5m-*-R=1m'0= 198944.447925 50Time Since Hole Cored (days)75100TRI-6344-576-0Figure 7·19.Simulated Formation Pore Pressures at Selected Radial Distances from the Test ZoneDuring C2H01·C Testing.account for the observed response, but how or whythis could have occurred is unknown. At the end ofthe monitoring period, the guard-zone pressure was2.22 MPa and increasing.7.1.4 C2H02. Borehole C2H02 was drilled at adownward angle of 45' to allow testing of Marker Bed139 beneath the west rib of Room C2 (Figure 5-2).Figure 7-20 shows the configuration of the test tool inC2H02, and indicates the lengths and stratigraphiclocations of the guard and test zones. The test zoneincluded all but the upper 27 cm of Marker Bed 139, aswell as 18 cm of the underlying halite. The guard zoneincluded the lower part of map unit 0 (halite) and theupper part of the polyhalitic halite overlying MarkerBed 139.Figure 7-21 is a plot of the test- and guard-zone fluidpressuredatacolleeted by the DASduringthe monitoringperiod. The testing sequence consisted of an initialbuildup period, followed by a pulse-withdrawal test thatwas aborted after the valves on the zone vent lineswere accidentally opened, a pulse injection to acceleratethe equilibration between the borehole and formationpore pressures, and two pulse-withdrawal tests(Figure 7-21). Following the second successful pulsewithdrawaltest, the pressure in the test zone wasdecreased during a gas-sampling exercise. A secondgas sample was collected six days later, after whichmonitoring was discontinued (Saulnier et aI., 1991).Interpretations of the tests performed in the test zone,as well as of the fluid-pressure responses observed inthe guard zone, are discussed below.7.1.4.1 Test Zone. The model used in theanalysis of the pulse-withdrawal tests assumes radialflow in the horizontal plane as described in Sections6.1 and 6.2. Cinco et al. (1975) showed that standardradial-flow solution techniques could be applied to theinterpretation of tests performed in slanted wells byconsidering the vertical, rather than slanted, penetrationdistance of the well as the production thickness.65


BOREHOLE C2H02TEST TOOL: #4DATE 04/20/89DEPTH OF HOLE: 10,856 m,MEASUREMENTS IN METERSFROM FLOOR BEFOREINFLATIONGUARD-ZONEPACKER# 30416C2H02TEST- TOOL CONFIGURATIONTOOLEXTENSION -~~BOREHOLECOLLARWALL~_/IBOREHOLE STRATIGRAPHYIo 00 ...,.,.....-.....,--:M-:cA'""P-;-:cUN"'I~T7c-/ "/~ - -MEDIUM TO COARSE HALITE, GRAY/0 25~+-__+---,lc;NT-,-,EoCR",C"-RY,-,S",TA",L",L"-,IN~E-,C,,,,'LA"'Y~ --I(0 18) X MAP UNIT 5X ~MEDIUM TO COARSE, COLORLESS TO ORANGE,HALITE, MINOR POLYHALITE/ X//2 15 ~+---+---=---:-c:-=--=-----------------t(152) M~~O~~~TE,5COLORLESS HALITE2,35 ~+---_-+-M-AP-U""N~IT-4---------------t(166) -COARSE TO FINE ARGILLACEOUS HAlITEJAB ~+---=-+--M-Apc--U-N-=IT-J'c-----------------I(2,46) X - -FINE, GRAY TO ORANGE HALITE, MINOR POLYHAlITE- X AND CLAY4,OD ~+----+-:-:M-;-;AP-=-U""N-=IT-2;;:-----------------t(283) -COARSE ARGILLACEOUS HALITE4 45 ~+-X-""---+-M-AP;;:-U""N-=IT-""--l---------------1(J,15) X X -MEDIUM, DRANGE POLYHALITIC HALITE4,75 ~+---+_-----------------~(J,36) M~~O~~~TE Ow FINE DOWNSECTION, COLORLESS TDGRAY, TRACE TO MINOR CLAY, HALITEenen!TEST -ZONEPACKERH 3041,11"'- 1005710,1J410212"~-lD.692-TEST-ZONETD,-10856 TRANSDUCER PORTY-------~ 7,59."------ 7 601GUARD-lONETRANSDuCER PORTwZoNIoa::


109 -0- Test Zone-0- Guard Zone8Test C2H02, Room C27 Borehole Oriented 45°Downward from Horizontal6 Test Zone 9.47-1 O.86mC? Marker Bed 1390-5::2:Q)... 4:::::lIf)3....If)Q)0- 2Time (1989 Calendar Days)TRI-6344-577-0Figure 7-21.Test- and Guard-Zone Fluid-Pressure Data from C2H02 Testing.Because C2H02 was drilled at a downward angle of45' and included most of the essentially horizontalMarker Bed 139 in the test zone, tests of this intervalwere analyzed using an idealized test-zone geometry.Flow from Marker Bed 139 to the borehole was assumedto be horizontal only, and the test zone wasmodeled as a vertical cylindrical borehole with a circumferenceequivalent to that of the ellipse formed bythe intersection of the 45' borehole and the horizontalmarker bed, and with a height equal to the verticalthickness of that portion of the marker bed containedwithin the test interval (Figure 7-22). The test-intervalvolume was maintained at its actual value by adding anappropriate "dead volume" to the test-interval volumecalculated by the model from the specified idealizeddimensions. This procedural step satisfies the modeltest-interval-compressibility boundary condition.During each pulse withdrawal, more fluid was removedfrom the test zone to produce a given pressure reductionthan the amount predicted based on thecompressibility ofbrine. Thetest-zone compressibilitiescalculated from the data collected during the secondand third pulse withdrawals were 1.05 x 10- 8 and 9.28x 10- 9 Pa- 1 , respectively (Table 6-3). Thebrine producedduring the pulse withdrawals degassed visibly in thecollection vessel. At the conclusion of the C2H02testing, samples of the gas from the test zone werecollected and analyzed. As reported in Saulnier et al.(1991), the gas was determined to be 91% hydrogen,6.5% nitrogen, and minor amounts ofoxygen, methane,argon, and carbon dioxide. The aluminumcomponentsof the test tool were found to be severely corrodedwhen the tool was removed from the hole. Thehydrogen gas was apparently generated during thecorrosion of the tool.Figure 7-23 shows the best-fit model simulation of theC2H02 pu Ise-withdrawal tests assuming porous, ratherthan fracture, flow. The observed fluid-pressure datafrom the test zone are also presented on the figure.The data from the time of penetration of the center of67


ActualIdealizedPlanViewCross1Section105 cml~~j~ 1"'-12.618 cmTRI-6344-121-0Figure 7-22.SChematic Illustration of the Actual and Idealized Test-Zone Geometry Used for theAnalysis of the C2H02 Tests.9.57.50 Data- SimulationC?0-~-Q)....::Jl/)l/)~a..5.53.51.5}- HistoryTesl C2H02. Room C2Borehole Oriented 45° Downward from HorizontalTest Zone 9.47 - 10.86 m, Marker Bed 139Simulated Vertical Thickness 0.86 mK 5.7 X 10- 13 mls (k = 8 X 10- 20 m 2 )55 = 1.4 X10- 7 m·1p' = 9.30 MPaCtz = 9.87 X 10- 9 Pa- 1HislorSimulation-0.5 ~::;:::;:::C;:::::L::::;:::;::r::;:::;::;~~::::;::::;:L::;:::::;::;::tj::;:::;:::::.;:r:::::L::::;:~C;:::;::::;:;:j:;:::::L::::;:::;::r::;:::;::;t:.Jo 25 50 75 100 125 150 175 200 225 250to _1989107.3905Time Since Hole Cored (days)TRI-6344-57B-0Figure 7·23.Best-Fit Model Simulation of the Test-Zone Fluid-Pressure Response During C2H02Testing.68


the test zone by drilling through the first minutesfollowing the pulse injectionwere included as specifiedpressurehistory, as were the data collected during thefirst minutes following each pulse withdrawal. Thespecified parameters used to simulate the last twopulse-withdrawal tests were a formation thickness of0.86 m (corresponding to the vertical thickness of onlythe marker bed portion of the test interval), a specificstorage of 1.4x 10- 7 m- 1 ,and atest-zone compressibilijyof 9.87 x 10- 9 Pa- 1 • The fitled parameters were ahydraulic conductivity of 5.7x 10- 13 mls (permeability of8x 10- 20 m 2 ) andaformation pore pressure of 9.30 MPa.Additional simulations showing the sensitivity of thebest-fit modelto slightchanges in hydrauIicconductivity,formation pore pressure, specific storage, and testzonecompressibility, as well as to the presence orabsence of test-zane-volume compensations, arepresented in Section 7.2.The well-test-analysis model was used to examine theradius of influence of the C2H02 testing, again assumingporous flow. Figure 7-24 shows the simulatedpressures at different radial distances from the boreholethroughout the entire testing period. The longestduration, highest magnitude response was caused bythe initial open-hole and buildup periods. The simulatedeffects of this depressurization had propagatedto a distance of about 20 m from the hole by the end ofthe monitoring period. The effects of the individualpulse tests can be seen as minor changes in the slopesof the pressure curvesto a distance of at least5mfromthe hole. In the case of the 5-m pressure curve, thesechanges in slope occura few days after the pulses. Asdiscussed with respect to the testing of Marker Bed139 in C2H01-C (Section 7.1.3.1), the radius of influenceof the C2H02 tests would be greater if flowthrough Marker Bed 139 is confined to fractures.7.1.4.2 Guard Zone. After first being shut inon April 24, 1989 (Calendar Day 114), the guard zonefailed to pressurize as expected (Figure 7-21). Thetubing from the control panel to the guard zone wasreplaced on May 17 (Calendar Day 137), butthe guardzone still did not pressurize as expected. On June 22(Calendar Day 173), the guard zone was vented andthe guard-zone packer was deflated. Brine was circulatedthrough the guard-zone vent and injection lines,and the packer was reinflated. After the guard zonewas shut in on June 23 (Calendar Day 174), a typicalpressure buildup was observed. An increase in theguard-zane-packer pressure on August 3 (CalendarDay 215) caused a slight increase in the fluid pressurein the guard zone, and the pulse withdrawal from thetest zone on August 18 (Calendar Day 230) caused theguard-zone pressure to decrease slightly. Three dayslater, the test- and guard-zone vent valves of the testtool were inadvertently opened during preparations forthe drillingof borehole C2H03, causing the guard-zonepressure to decrease. After the valves were closed,the guard-zone pressure began to rise again, but at alower rate than that observed afterthe June 23 shut-in.The guard-zone fluid pressure continued to rise at arelatively constant rate for the remainder of the monitoringperiod.The relatively constant rate at which the guard-zonefluid pressure increased between August 22, 1989(Calendar Day 234) and December 12,1989 (CalendarDay 346) is anomalous (Figure 7-21). A steadilydecreasing rate ofpressure rise, such as thatobservedafterthe shut-in on June 23 (Calendar Day 174), is theexpected response following a shut-in (Figure 4-6).Some type of equipment failure, perhaps a leak fromthe guard-zone packer (Figure 0-8), may have beenresponsible forthe observed behavior. No quantitativeinterpretation can be made from the fluid-pressureresponses observed in the guard zone during theC2H02 testing. The formation pore pressure of theguard-zone interval, however, must be greater than 3MPa, the highest pressure observed during the monitoringperiod.69


9ctl0-~-Q).....:::l(/)(/)Q).....0-S76--e-R=20m--e- R = 10 m-A- R= 5m--+-R=2m-*-R=1m5L.................L..J.................~...................-...J.-.....................L...a.................J...L.............o...JL....L.............L...l.................L-l.........................L-.....................o255075 100125150 175to - 1989 107.3905Time Since Hole Cored (days)200225250TRI-6344-579-0Figure 7-24.Simulated Formation Pore Pressures at Selected Radial Distances from the Test ZoneDuring C2H02 Testing.7.1.5 C2H03. Borehole C2H03 is a horizontal boreholedrilled 2.1 m above the floor of Room C2 betweenanhydrites "a" and "b" on August 22 and 23, 1989(Calendar Days 234 and 235). Figure 7-25 shows theconfiguration of the test tool in C2H03 as installed onAugust 24 and 25, 1989 (Calendar Days 236 and 237).The test zone in C2H03 extended from 7.76 to 9.14 mfrom the ribofthe room, while the guard zone extendedfrom 5.90 to 6.92 m. C2H03 was drilled entirely in mapunit 9, which consists of pure halite with only tracequantities of clay and polyhalite (Appendix C).Figure 7-26 is a plot of the test- and guard-zone fluidpressuredata collected by the DAS during the 30-daymonitoring period following the shut in of the test andguard zones on August 29,1989 (Calendar Day 241).Before the test and guard zones were shut in, theirfluidpressures were 0.054 and 0.056 MPa, respectively.These values were not expected to be zero, becausethe hole was higher than the transducers, which weremounted outsidethe hole onthe instrumentationtrailer.The elevation head between the hole and the transducerswas calculated to be only about 0.01 MPa,however. The difference between the observed andcalculated values probably reflects the difficulty inachieving accurate transducer readings nearthe lowerlimit of a transducer's range rather than actual pressuresor pressure differences. As the intervals wereshut in, the test- and guard-zone pressures increasedto 0.067 and 0.1 01 MPa, respectively, asthefluid inthezones was compressed slightly. After shut in, the testandguard-zone pressures were monitored for 30days. The zones' fluid pressures decreased slightlyduring the shut-in period. Because of the lack of anypressure buildup during the shut-in period, testing wasended and the test tool was removed from C2H03 onSeptember 29, 1989 (Calendar Day 272).7.1.5.1 TestZone. As shown on Figure 7-26,the fluid pressure in the C2H03 test zone did notincrease during the 30-day shut-in period, but insteaddecreased by about 0.01 MPa. Testing of multipacker70


BOREHOLE: C2H03TEST TOOL #5DATE 08/28/89DEPTH OF HOLE: 9.144 m.9.14BOREHOLESTRATIGRAPHY0.00MAP UNIT 9- MEDIUM TO COARSELY CRYSTALLINE HALITE, PALE YELLOW, TRACESOF INTERCRYSTALLINE GRAY CLAY AND POLYHALITEC2H03TEST - TOOL CONFIGURATION7.76* 692. 590*1------TEST - ZONE------IGUARD -ZONEGUARD-ZONETRANSDUCERPORTTOOLEXTENSION4.995 0.105TEST -ZONETRANSDUCERPORTTEST -ZONEPACKER# 3041 12GUARD -ZONEPACKER# 3041 101.945NOTE MEASUREMENTS IN METERS FROM WALLBEFORE INFLATION.ESTIMATED POSITION AFTER INFLATION.Figure 7-25.Configuration of Multipacker Test Tool #5 for Penneability Testing in Borehole C2H03.71


0.11~ hcaa..0.09~ 0.07......-Q) In-....~~:::::ll/ll/l~ 0.05 a..0.03~245250255260265-0- Test Zone I1-0- Guard Zone0.01 L..-L-................I...-.L.....l.-................I...-.L.....l.--'-...........L-.........--J.............L-.L...I--J.............L-.L...I'--I.....................L.....J.........-................240Time (1989 Calendar Days)270275TRI·6344-580-0Figure 7-26.Test- and Guard-Zone Fluid-Pressure Data from C2H03 Testing.test tool #5 before and after the C2H03 testing revealedno problems that could have caused the tool tofail to hold pressure during the testing. Therefore, theobserved behavior is thought to be representative ofthe formation response to the testing conditions.Forthe shut-in pressure to decrease, a combination ofevents would have to occur. First, the test-zonevolume would have to increase slightly. This couldoccur in response to packer readjustment or holeelongation. Second, little or no inflow from the formationwould also be required, implying very low formationpermeability. Two possible conditions could explaina lackof inflow to the borehole. First, the relativelypure halite of map unit 9 may not have continuousinterconnected porosity that would lead to permeability.Second, map unit 9 may have continuous interconnectedporosity, but the permeability may be so lowthat no observable pressure response could occur onthe time scale of the monitoring period. The firstpossibility cannot be evaluated with the available data;a much longer monitoring period and perhaps a differenttype of testing would be required to establish thecomplete absence of permeability. The second possibilitycanbe evaluated, at least qualitatively, byconsideringthe pressure responses that would be expectedto occur given a range of permeability (hydraulic conductivity)values.Before simulations can be performed showing whatthe formation response might be given different valuesof hydraulic conductivity, a value for test-zone compressibilitymust be specified. No pulse withdrawalswere performed in C2H03 that would have provideddata with which to evaluate test-zone compreSSibility,so a value must be estimated. Air may have beenentrapped in C2H03 during test-tool installation becauseof the hole's orientation. Different procedureswere followed to install the test tool in the horizontalC2H03 borehole than those used in downward-angledholes. Thetoolwas installed inthe emptyborehole andthe guard-zone packer was inflated. The hole was72


then evacuated with a vacuum pump, after which thehole was filled with brine and the test-zone packerwasinflated. Brine was then circulated through the .guardand test zones using the vent and transducer lines totry to remove residual trapped air. Recent testing intransparent Lexan casing has shown these proceduresto be inadequate in removing entrapped air.After following these procedures, approximately onepercent of the test-zone volume and three percent ofthe guard-zone volume may still be occupied by air.The presence of this amount of air would make thecompressibility of the test zone considerably higherthan that of brine alone. The actual value of test-zonecompressibility for the C2H03 testing, however, cannotbe evaluated with the available data.An upper bound on the compressibility of the test zonecan be approximated by considering the compressibilityof an ideal gas. The compressibility of an ideal gasis given by the inverse of the absolute pressure of thegas (Craft and Hawkins, 1959). At the start of the shutinperiod, the test-zone pressure in C2H03 was 0.067MPa (0.167 MPa absolute pressure). The theoreticalmaximum compressibility of the test zone, therefore,was6.0x 10- 6 Pa- 1 • This value was usedto evaluate thefluid-pressure responses that might have been observedduring the C2H03 testing given a range ofhydraulic-conductivity values.A suite of simulations was performed showing theresponses that would have been expected during theC2H03 testing, given the test-zone compressibilitypresented above and a range of hydraulic conductivityvalues and other formation parameters. These simulationswere obtained by assuming that the formationpore pressure was 11 MPa. This pressure was selectedbecause it is approximately the highest pressureyet observed during this testing program andmay, if the Salado is truly a porous medium withcontinuously interconnected porosity, represent thepressure to be expected at the WIPP facility horizon inthe absence of excavation-related depressurization.Presumably, if the permeability of map unit 9 is so lowas to preclude any observable pressure responseduring the C2H03 testing, then that same low permeabilityshould have prevented significant depressurizationat the test-zone depth from the excavation ofRoom C2. Specific storage for the simulations wasassumed to be 9.5 x 1O-s m- 1 • The simulations assumeradial flow to the borehole, which in the case of thehorizontal borehole C2H03, may be a questionableassumption. Given the lack of an observed pressurebuildupresponse, however, use of a more complexmodel designed specifically for tests in horizontalholes appears unwarranted at this time.Figure 7-27 shows the results of these simulations. Ata hydraulicconductivity ~ 10- 14 mts, less than 0.01 MPapressure buildup would have occurred dUring themonitoring period. At a hydraulic conductivity of 10- 13mts, a few hundredths of an MPa pressure increasewould have been observed, while at a hydraUlic conductivityof 10- 12 mIs, the pressure would have increasedby a few tenths of an MPa. If the test-zonecompressibility was less than the value assumed forthese simulations, then the simulations shown in Figure7-27 would be representative of proportionallylower hydraulic conductivities. Considering that nopressure buildup at all was observed, we might concludethat the hydraulic conductivity of the relativelypure halite around C2H03 is less than 10- 14 mts. Thismay be a conservatively high upper bound on thehydraulic conductiVity around C2H03, considering theresponses observed during testing of the C2H01-Bguard zone, which had an interpreted hydraulic conductivityof1.4 x 10- 14 mls (Figure 7-14).Finley (personal communication) has attempted tomeasure brine inflow to 1O-em-diameter holes drilledhorizontally into map unit 9 from Room D (see Figure5-1). Over a monitoring period of more than threeyears, no observable brine inflow to the holes has been73


0.4 r-r"-.-.......,....,...,,....-r"'T"""r-r"-.-.......,....,...,,...,..."'T"""r-r-.-.......,....,...,,...,..."'T"""r-r-.-.,..-,..,...~....,....,....,Test C2H03. Room C2~ Dsal'mtaulatl'On Test Zone 7.76 - 9.14 m, HorizontalHalite, Map Unit 9cua.~Q)L-:::J(/l(/lQ)L-a.0.30.20.1Ss = 6.0 X 10- 7 m- 1 K1p. = 11 MPaC tz= 6 X 10. 6 Pa· 1o00000000000000000K 4 = 1 X 10. 15 mls510152025303540to - 1989235.4200Time Since Hole Cored (days)TRI-6344-581·0Figure 7-27.Simulated Test-Zone Fluid-Pressure Response In Borehole C2H03 Using a FormationPore Pressure of 11 MPa, a Test-Zone Compressibility of 6 x 10- 6 Pa' l , and VaryingHydraulic Conductivity.detected, providing further indication of small or nonexistentpermeability in the pure halite of map unit 9.The simulations discussed above are highly speculativeand are only presented in an attempt to give anupper bound on the hydraulic conductivity of relativelypure halite, based on an underlying assumption thatmap unit 9 has some permeability and pore pressure.When similar hydraulic behavior is encountered infuture test holes, additional testing will be performed totry to address questions about the presence or absenceof pore pressure and permeability more directly.7.1.5.2 Guard Zone. Figure 7-26 shows thatthe fluid pressure in the guard zone of C2H03 decreasedfrom 0.101 MPa to 0.092 MPa during the first15 days of the shut-in period, and was then stable forthe next 15 days. The absence of a buildup responseprecludes any quantitative evaluation of formationhydraulic properties. The discussion and qualitativeevaluation of the test-zone response presented inSection 7.1.5.1 applies equally well to the guard-zoneresponse.7.1.6 N4PSO. Borehole N4P50 was drilled in the North1420 drift in December 1988. One test tool wasinstalled in December, but was removed 18 days laterbecause of suspected problems with electrical connections.A second test tool was installed on January6, 1989, and the test and guard zones were shut in onJanuary 12, 1989. The test zone for both installationsincluded anhydrite "c" and clay B (Figure 7-28). Thesecond tool had to be removed from the hole onFebruary 6, 1989 because of construction activitynearby. Due to the length of the construction period,borehole N4P50 was later abandoned.Figure 7-29 shows the fluid-pressure buildups observedin the test and guard zones in N4P50. The testzonedata give only an indication of a relatively rapid74


N4P50 TEST ~ TOOL CONFIGURATIONBOREHOI_t': N4P50TEST TOOL #4DATE 01/06/89HOLE DEPTH 10871MEASUREMENTS Ir'JMETERS FROM FLOORf-3EFORE INFLf\TI()~~* ESm,~ATED POSI1IO>JI\FTER PI\CKlRI~~FLATION,zmlE~)ACKERGUARD#3041 1 __~flTOOLEXTENSiON- 62031- - -0~00 --1 --~-c 1 POLYHALlTE, ARGILLACEOUS--- HALITE1 451.552.473.454.65483S 26655-,_... '''''' co,",",, "'"X X XPOLYHALITIC HALITE- COARSE, ORANGE TO GRAY,@) IS7~-- C;CATTERED ORANGE ANHYDRITEMARKER BED 139"-" " -MICROCRYSTALLINE, GRAY TOORANGE, FRACTURE AT 1 55 m,":" ""-","HALITECLAY E - --- FINE TO COARSE, COLORLESS- - TO LIGhT ORANGE. ARGILLA.CEOUS.-INCREASING POLYHALITE WITHX. X X DEPTHXPOLYHALITIC HALITEX -- MEDIUM TO VERY COARSE,---. IS7 ~ SCATTERED ORANGE ANHYDRITEX X AT 4.65 mHALITECLAYJ _.--,----FINE TO f.,1EDIUf,


-0- Test Zone-0- Guard Zone0.80.0-0.2350ca 0.60..:2- CD 0.4 ...:::1lJ)lJ)CD...0.. 0.2Test N4P50, North 1420 DriftTest Zone 9.51 - 10.67 m, Vertically DownArgillaceous Halite 'c'360 370 380 390 400 410Time (1988 Calendar Days)TRI-6344-5B2·0Figure 7-29. Test- and Guard-Zone Fluid-Pressure Data from N4P50 Testing.flUid-pressure buildup following shut-in; no pressurestabilization was achieved. The guard-zone datashow a slower rate of pressure rise. No pulse testswere conducted in N4P50. The available fluid-pressuredata are not sufficient to allow quantitative interpretationof formation parameters.7.1.7 L4P51-A. Borehole L4P51 was drilled verticallydownward into the floor of Room L4 in October 1989(Section 5.3). Because the hole was laterdeepened toallow testing of anhydr~e "c, Uthe testing performedwith the original hole configuration is given an "AUsuffix. The test-tool configuration for the L4P51-Atesting allowed monitoring of Marker Bed 139 in theguard zone, and underlying halite, polyhalitic halite,and clay D in the test zone (Figure 7-30).Figure 7-31 shows a plot of the flUid-pressure datafrom the test and guard zones collected during theL4P51-A testing. The testing sequence in the testzone consisted of an initial buildup period followed bytwo pulse-withdrawal tests. A constant-pressure flowtest was conducted in the guard zone beginningMarch 1, 1990 (1989 Calendar Day 425). Thattestwillbe discussed and interpreted in a subsequent report.Interpretations of the pulse-withdrawal tests in the testzone, and discussion of the fluid pressures observedin the guard zone during those tests, are presentedbelow.7.1.7.1 Test Zone. The initial pressurebUildUp in L4P51-A produced a non-characteristicbuildup curve (Figure 7-31) similar to those describedfor the C2H01-B, C2H01-C, and C2H02 test zones inSections 7.1.2.1, 7.1.3.1, and 7.1.4.1. The samefactors that could have caused the compressibility ofthe test zone to be dependent on pressure in thosecases might also have been operative in this case, withthe exception that all of the aluminum test-tool componentsused during earlier testing had been replacedwith stainless steel components for the L4P51-Atesting, thereby eliminating the potential for gas76


L4P51-ATEST-TOOL CONFIGURATIONBOREHOLE: L4P51TEST TOOL: #3DATE: 10/23/89DEPTH OF HOLE: 4.75 m.FLOORBOREHOLESTRATIGRAPHY000 ---.---~-------------IMAP UNIT 0- HALITE WITH ISOLATEDBLEBS OF GRAYCLAYT- 1wZoNIo[LGUARD-ZONEPACKER#304112 __«=:JoL 249*-.-/wis LVDT # R-10NIf­U1Wf-TEST -ZONEPACKER#30419 ~---.---:~ 3 33*--LVDT # R-04LVDT # R-01LVDT # A-04 __- 2.016-GUARD-ZONETRANSDUCER PORT-~- 3.830-3.920-I--~- 3997-+--~4072--4.163__ 4.516TEST -ZONETRANSDUCER PORT---4.694- T.0-4.75 4.75 _--L__--'NOTE MEASUREMENTS IN METERS FROM FLOOR BEFORE* ESTIMATED POSITION AFTER PACKER INFLATION.0.45 ----1-----+---------____ X POLYHALITIC HALITE- MINORXINTERCRYSTALLI NEX GRAY CLAY- X -·1 .50 ----I--~~-+-M-,-A-cR=-K-E-R---:B=-E=0=--l-c3=-9=------1230 =1~~iJCdL2A~Y~E=======12.36 HALITE- ISOLATED BLEBSOF GRAY CLAY2 58 -~--...I,-CLAY PARTING--------1- XXXXXxx- ANHYDRITEPOLYHALITIC HALITE- FINE TO COARSELYCRYSTALLINE WITHVARIABLE AMOUNTSOF INTERCRYSTALLINEGRAY CLAY4.55 :::=.~~PCILA~Y::::QD=======j4.57HALITE- MINORINTERCRYSTALLINEGRAY CLAYINFLATIONFigure 7-30.Configuration of Multlpacker Test Tool #3 In Borehole L4P51 for L4P51-A Testing.77


generation through aluminum corrosion. The testzonecompressibilities calculated for the two pulsewithdrawals, 7.01 x 10- 10 and 7.31 x 10- 10 Pa- 1 (Table 6­3), are only slightly higherthan the estimated compressibilityofthetest-zone brine, 3.1 x 10- 10 Pa- 1 • Nofreegaswas observed during the pulse withdrawals, althoughthe brine withdrawn degassed visibly in the collectionvessel (Saulnier et aI., 1991)_Duringthe L4P51-Atesting, each successive pressurebuildup appeared to be trending towards a lowerpressure thanthe previous buildup (Figure 7-31). Thispattern of response is typically observed during depletionof a finite reservoir. Therefore, a zero-flow conditionwas used for the external boundary of the modelfor the L4P51-A simulations_ The distance to thisboundary was one of the parameters mted during testinterpretation.The apparent depletion response observed during theL4P51-A testing is puzzling. No reason is known forpermeability to disappear over a distance of a fewmeters. Therefore, other factors in addition to a zeroflowboundary that could cause an apparent depletionresponse during hydraulic testing should also be considered.The rock surrounding the WIPP excavations should becontinually losing pressure to the excavations. Inaddition, open boreholes throughout the WI PP undergroundfacility should be causing depressurization ofall strata they penetrate. Depressurization from eitherof these sources could, at least locally, be observableon the time scale of our testing. A continuous depressurizationsuperimposed on the formation response tothe testing could have produced a composite responsesimilar to that observed.Figure 7-32 shows the best-fit model simulation of theL4P51-A pulse-withdrawal tests along with the observedfluid-pressure data from the test zone. Thedata from the time of penetration of the center of thetest zone by drilling to the first pulse withdrawal wereincluded as specified-pressure history, as were thedata collected during the first minutes following eachpulse withdrawal. The specified parameters used tosimulate the two pulse-withdrawal tests were a formationthickness of 1.42 m, a specific storage of 1.3 x 10­7 m- 1 , and a test-zone compressibility of 7_16 x 10- 10Pa- 1 • The mted parameters were a hydraUlic conductivityof 4.5 x 10- 14 m/s (permeability of 6 x 10- 21 m 2 ), aformation pore pressure of 2.75 MPa, and a distanceto the zero-flow boundary of 2.0 m. Additional simulationsshowing the sensitivity of the best-fit model toslight changes in hydraulic conductivity, formationpore pressure, specific storage, test-zone compresssibility,and distance to the zero-flow boundary,as well as to the presence or absence of test-zonevolumeand temperature compensations, are presentedin Section 7.2.In this particular case, the test zone was less than onemeter below Marker Bed 139. The guard-zone-pressuremonitoring during the L4P51-A testing showedthat the pressure in Marker Bed 139 was only 0.2 to0.3 MPa (Figure 7-31). Thus, a significant pressuregradient was present between the test zone andMarkerBed 139. Flowfromthe interval spanned by thetest zone to Marker Bed 139 could have resulted in aloss of pressure from the test-zone interval. If thisprocess were in fact operative, however, we wouldexpect to see a continual decline in the test-zonepressure with time as the depressurization continued.Continued monitoring of the test-zone pressure for aperiod of three months during testing in the guard zoneshowed little or no net depressurization (Figure 7-31).After recovering from the second pulse-withdrawaltest to a peak pressure of 2.24 MPa, the test-zonepressure did decline slightly, to 2.18 MPa, over aperiod of approximately 40 days. However, the simulationindicates that the pressure decreased from2.75 MPa when the borehole was first drilled to78


3.02.5Test L4P51-A, Room L4Test Zone 3.33 - 4.75 m, Vertically DownArgillaceous Halite Including Clay D~ Test Zone-0- Guard Zone2.0'@'0-::2: 1.5Q)....::J...


2.24 MPa about 130 days later, when the pressurepeaked following the second pulse withdrawal. If thisdepressurization had continued linearlyforthe next 40days, the pressure "'!ould have dropped to about2.08 MPa, not 2.18 MPa. Moreover, overthe following60 days, the test-zone pressure did not drop at all, butrose to approximately 2.21 MPa. Continuous loss ofpressure from the test-zone interval to Marker Bed 139does not, therefore, appear to be a plausible explanationfor the pressure depletion observed during theL4P51-A testing.The nearest open borehole to L4P51 is N4P50, 20 maway (Figure 5-1). The potential for depressurizationof a test interval by leakage into a hole 20 m awayshould be much less than the potential for leakage intoa relatively underpressurized stratum only one meterabove the test interval. Leakage into N4P50 shouldalso have resulted in a continuing depressurization atL4P51 ,which was not observed. Thus, depressurizationby leakage into borehole N4P50 also does notappear to be a plausible explanation for the apparentpressure depletion of the L4P51-A test interval.If no external pressure sink caused the pressuredepletion, the cause may lie in the rock itself. Theapparent zero-permeability boundary could be explainedif most of the brine in communication with thehole was contained within discontinuous clay stringers.The brine in these stringers could be depletedrelatively rapidly, and recharged slowly (if at all) bybrine contained within halite or by brine containedwithin other clay stringers with low-permeability connectionsto those depleted. Alternatively, stresschanges around a borehole could create a ring ofincreased permeability, surrounded by lower permeabilitymaterial. In this case, the high-permeability ringcould depressurize faster than the surrounding materialcould recharge it. If the basic concept of a finiteinner permeable region surrounded by an outer regionof lower (or nonexistent) permeability is correct, weshould be able to obtain at least temporary pressurestabilization at successively higher levels by performinga series of pulse injections on the interval.Thisprocedure will be attempted at the next opportunity.The rise in the test-zone fluid pressure observed overthe last 50 to 60 days of monitoring could have beencaused by either or both of two factors. First, thepressure rise could have been caused by boreholeclosure compressing the fluid in the test zone. Problemswith a-ring compression (see Section D.2 ofAppendix D) rendered the radial LVDT data fromL4P51-A unreliable in evaluating borehole deformationearly in the testing period, but the late-time closureindicated by the LVDTs (Figure D-2) is believed to beat least qualitatively reliable. Second, the fluid pressurecould have increased due to slow recharge of thedepleted volume of rock from surrounding lower permeabilitymaterial.7.1.7.2 Guard Zone. The guard zone duringthe L4P51-A testing included Marker Bed 139, clay E,and a few centimeters of halite above and below(Figure 7-30). After the guard zone was shut in onOctober 27, 1989 (Calendar Day 300), the fluid pressurestabilized quickly at about 0.28 MPa. The guardzonepressure decreased slowly during the testing inthe test zone, reaching about 0.20 MPa on March 1,1990 (1989 Calendar Day 425). On that date, aconstant-pressure flow test was initiated in the guardzone. That test will be discussed and interpreted in asubsequent report.Fluid pressures of up to 10 MPa have been observedin Marker Bed 139 at other locations where the markerbed is farther removed from the excavations than inRoom L4 (boreholes C2H01 and C2H02, and Petersonet al. [1987]). The low observed pressure in L4P51 ofonly 0.28 MPa and subsequent decrease may be80


elated to a general and on-going depressurization ofMarker Bed 139 under the room, possibly throughfractures developing in the DRZ around the room.end of testing. Thus, as was the case in C2H02(Section 7.1.4.1), hydrogen gas was probably generatedas the corrosion occurred.7.1.8 SOP01. Borehole SOP01 was drilled verticallydownward inthe f1oorofthe South 1300 drift. Figure 7­33 shows the configuration of the test tool in SOP01and indicates the lengths and stratigraphic locations ofthe guard and test zones. The test zone included haliteand polyhalitic halite underlying Marker Bed 139 andclay D. At this location, clay D is approximateIy one cmthick (Appendix C). The guard zone included all but theupper few centimeters of Marker Bed 139, and a fewcentimeters of the underlying halite.Figure 7-34 is a plot of the test- and guard-zone fluidpressuredatacollected bythe DAS during the monitoringperiod. The testing sequence in the test zoneconsisted of an initial buildup period followed by twopulse-withdrawal tests. Following the second pulsewithdrawaltest, the pressure in the test-zone wasdecreased during a gas-sampling exercise (Saulnieret aI., 1991). Monitoring was terminated 11 days later.A pulse-withdrawal test was also attempted in theguard zone. Interpretations of the tests performed inSOP01 are presented below.7.1.8.1 TestZone. DuringbothSOP01 pulsewithdrawals, unknown quantities of gas were producedalong with brine. Test-zone compressibilitieswere calculated only on the basis of the volumes ofbrine removed. The test-zone compressibilities calculatedfrom the first and second pulse-w~hdrawal datawere 1.47 x 10. 8 and 1.96 x 10. 8 Pa·1, respectively(Table 6-3). These values are nearly two orders ofmagnitUde higher than the compressibility of brine,probably reflecting the presence of gas in the testzone. The test tool used in SOP01 had aluminumcomponents, which were found to be severely corrodedwhen the tool was removed from the hole at theFigure 7-35 shows the best-fit model simulation of theSOP01 test response. Only the data from the time ofdrilling to the initial shut-in nine days later, as well asthe data collected during the first minutes following thepulse withdrawals, were included as specified-pressurehistory. Because the initial buildUp occurred at acontinually decreasing rate similar to the ideal behaviorshown on Figure 4-6, both the buildup and therecoveries from the pulse withdrawals were simulated.The simulation matches the observed data from theinitial buildup period and from the second pulse-withdrawaltest reasonably well, but deviates from the firstpulse-withdrawal test data.During the first pulsewithdrawaltest, a typical decreasing-slope curvaturewas observed for approximately the first 29 daysofthetest, followed by a relatively abrupt increase in slope.The reason for this change in behavior is unknown.Little weight was given, therefore, to the match betweenthe data and the simulation of the first pulsewithdrawaltest when determining the best-fit parameters.The specified parameters for the simulation were aformation thickness of 1.43 m, a specific storage of1.1 x 10. 7 m-', and a test-zone compressibility of1.70 x 10. 8 Pa-'. The fitted parameters were ahydraulic conductivity of 6.1 x 10- 14 mls (permeabilityof 8 x 10- 2 ' m 2 ) and a formation pore pressure of4.45 MPa. Additional simulations showing the sensitivityof the best-fit model to slight changes inhydraulic conductivity, formation pore pressure, specificstorage, and test-zone compressibility, as wellas to the presence or absence of test-zane-volumecompensations and temperature compensations,are presented in Section 7.2.81


SOP01TEST-TOOL CONFIGURATIONBOREHOLE: SOP01TEST TOOL #3DATE: 01/13/89DEPTH OF HOLE 5.170 m.w zoNGUARD -ZONEPACKER#3041.9--EXTENSIONBOREHOLESTRATIGRAPHY000 --~--~----------------IMAP UNIT 0- COARSELY CRYSTALLINECLEAR HALITE045 --1-----+-----------------1X POLYHALITIC HALITEX - COARSELY CRYSTALLINECLEAR TO ORANGE HALITEX - WITH MINOR POLYHALITEX180 ---l~~~-+-.-------------------1MARKER BED 139- ANHYDRITEo0::


5C? 30..:2Q)....::::l(J)(J)Q)....a.---- TestZoneTest SOP01, South 1300 Drift, East of E140 Drift-0- Guard Zone4Test Zone 3.74 - 5.17 m, Vertically DownArgillaceous Halite Including Clay D20-10 50 100 150Time (1989 Calendar days)200 250TRI-6344·585-QFigure 7-34.Test- and Guard-Zone Fluid-Pressure Data from SOP01 Testing.4.53.50 Data- SimulationTest SOP01, South 1300 Drift, East of E140 DriftTest Zone 3.74 - 5.17 m, Vertically DownArgillaceous Halite Including Clay DC?a. 2.5:2-~:::J(J)l/)(1)....a.1.50.5K = 6.1 X 10- 14 mls (k =8 x 10- 21 m 2 )S5 = 1.1 X 10- 7 m- 1p' = 4.45 MPaC tz= 1.7 x 10- 8 Pa- 11--


The well-test-analysis model was used to examine theradius of influence of the SOP01 testing. Figure 7-36shows simulated pressures at different radial distancesfrom the borehole throughout the entire testingperiod. The longest duration, highest magnijude responsewas caused by the initial open-hole and buildupperiods. The simulated effects ofthis depressurizationhad propagated to adistance of more than 8 mfrom thehole by the end of the monitoring period. The effectsof the individual pulse tests can be seen as minorchanges in the slopes of the pressure curves to adistance of at least 2 m from the hole. In the case ofthe2-m pressure curve, these changes in slope occur 5 to10 days after the pulses.7.1.8.2 Guard Zone. The fluid pressuresmeasured in the guard zone (Marker Bed 139) duringthe SOP01 testing are shown plotted in Figure 7-37.The initial buildup period was followed by a pulsewithdrawaltest. The behavior shown is anomalous inthe sense that the pressure-recovery curves exhibitrelatively abrupt decreases in slope, causing flatteningof the curves. During the initial bUildup period, the fluidpressure appeared to stabilize at about 0.49 MPa, andthen dropped to about 0.46 MPa for an unknownreason. Following the pulse withdrawal, the fluidpressure rose and stabilized at about 0.44 MPa forseveral weeks before starting to rise again.The pulse-withdrawal period for the SOP01 guardzonetest lasted about seven minutes (Saulnier et aI.,1991). During the first two minutes, 7.3 cm 3 of brinewere Withdrawn, but little orno pressure decrease wasnoted. During the next five minutes, only anunmeasured amount of gas was produced, and thepressure dropped from 0.46 to 0.23 MPa. When thetest tool was removed from the hole at the end oftesting, the aluminum mandrel within the guard zonewas found to be severely corroded. Thus, the gasobserved may have been largely hydrogen, as wasobserved in C2H02 (Section 7.1.4.1).Data are not available to allow calculation of the guardzonecompressibility at the time of the pulse withdrawal.The guard-zone compressibility also likelychanged during the testing period, as gas was generatedby corrosion of aluminum. As a result of thisuncertainty in the guard-zone compressibility, no definitiveinterpretation can be made of the test data.Simulations of the test can be performed, however,using a theoretical maximum value of guard-zonecompressibility. The hydraulic conductivity estimatedfrom these simulations should represent an upperbound on the actual value. The theoretical maximumcompressibility of the SOP01 guard zone is the compressibilityof an ideal gas at the pressure measured inthe guard zone. The compressibility of an ideal gas isgiven by the inverse of the absolute pressure ofthe gas(Craft and Hawkins, 1959). At the end of the pulsewithdrawal, the guard-zone pressure in SOP01 was0.23 MPa (0.33 MPaabsolute pressure). Thetheoreticalmaximum compressibility of the guard zone, therefore,was 3.0 x 10- 6 Pa-'.Figure 7-37 shows a simulation of the SOP01 guardzonetest response using the guard-zone compressibilityvalue determined above. The data from thetime of penetration of the midpoint of the guard zoneby drilling through the first minutes of the buildUpperiod were included as specified-pressure history,as were the data collected when the pressure decreasedfor an unknown reason near the end of thebuildup period. The data collected during the first15 hrafterthe pulse withdrawal, when little pressurebuildup was observed, were also included as specified-pressurehistory in the simulations. In additionto the specified guard-zone compressibility, the simulationused specified values of 0.90 m for formation84


4.74.4ca 4.10...~Q).... 3.8::J(J)(J)Q)....0... 3.53.22.90 25to. 1989 11.5935750 75 100 125 150 175Time Since Hole Cored (days)-e- R=8.0 m-e- R=4.0 m-Ir- R = 2.0 m-+-- R= 1.0 m-*- R =0.5 m200 225TRI-6344-587-0Figure 7-36.Simulated Formation Pore Pressures at Selected Radial Distances from the Test ZoneDuring SOP01 Testing.oData- Simulation0.4~ 0.2:::l(J)(J)~0...0.0Test SOP01- GZSouth 1300 Drift, East of E140 DriftGuard Zone 1.86 - 2.91 m, Vertically DownSimulation Thickness 0.90 m, Marker Bed 139K = 4.2 X 10- 11 m/s (k =6 X 10- 18 m 2 )Ss = 1.4 X 10- 7 m- 1p' = 0.52 MPaC gz = 3.0 X 10- 6 Pa- 1J- History.6 History255075100125150175200225250to· 1989 11.556Time Since Hole Cored (days)TR1-6344-588-0Figure 7-37.Best-Fit Model Simulation of the Guard-Zone Fluid-Pressure Response During SOP01Testing.85


thickness and 1.4 x 10- 7 m- 1 for specific storage. Thefitted parameters were a hydraulic conductivity of4.2 x 10- 11 m/s (permeability of 6 x 10- 18 m 2 ) and aformation pore pressure of 0.52 MPa.As discussed above, the compressibility of the guardzone probably increased during the SOP01 testing ashydrogen gas was generated by corrosion. Other gasmay have exsolved from the formation brine or beensupplied from the formation as an already separatephase during the testing. Thus, the assumption thatthe guard-zone compressibility could be representedby the compressibility of an ideal gas may have becomeincreasingly valid as the test duration increased.However, the simulation shown in Figure 7-37 matchesthe observed data better during the initial shut-inbuildup period than afterthe pulse withdrawal. Followingthe pulse withdrawal, the fluid pressure in the guardzone recovered relatively slowly compared to the rateat which it recovered following the initial shut in. Theinitial recovery following the pulse withdrawal wasparticularly slow, as little or no pressure increase wasobserved for 15 to 20 hr. Even after incorporating thefirst 15 hr after the pulse withdrawal as specifiedpressurehistory, the simulation still predicts a recoveryfaster than that observed. The curvature of the plot ofthe observed recovery data also differs from thatpredicted by the simulation, indicating that the modeldoes not incorporate all of the processes actuallyacting on the guard zone.In summary, the simulation of the SOP01 guard-zonetest response was not completely successful. Theinterpreted hydraUlic conductivity, 4.2 x 10- 11 mis, maybe reliable as an upper bound on the actual hydraulicconductivity, but uncertainties remain about the rolethat gas generation and/or flow may have played inproducing the observed fluid-pressure response. Nointerpretation was made of the possible radius ofinfluence of the SOP01 guard-zone testing because itwas considered to be too speCUlative in light of theuncertainties associated with the tests.7.1.9 S1P71-A. BoreholeS1P71 was drilled verticallydownward into the floor of Room 7 in Waste Panel 1 toa depth of 4.55 m in November 1988 (Section 5.5).Because the hole was later deepened to allow additionaltesting, the testing performed with the originalhole configuration is given an "A" suffix. Figure 7-38shows the configuration ofthe test tool in S1P71 duringthe S1 P71-A testing and indicates the lengths andstratigraphic locations of the guard and test zones.The guard zone encompassed Marker Bed 139 and afew centimeters of the overlying halite, while the testzone included halite and polyhalitic halite below MarkerBed 139, as well as clay D.Figure 7-39 is a plot of the test- and guard-zone fluidpressuredata collected during the monitoring period.After achieving a successful pressure-tight test-toolinstallation on the third try (Saulnier et al., 1991), thetesting sequence consisted of an initial pressurebuildupperiod followed by two pulse-withdrawal testsin the test zone. No pressure buildup was observed inthe guard zone during the entire monitoring period.Two pulse-injection tests were attempted in the guardzone, but in both cases the induced pressure dissipatedcompletely as soon as the guard zone wasshut in.7.1.9.1 Test Zone. During the S1 P71-Atesting, each successive pressure buildup appearedto be trending towards a lower pressure than theprevious buildup (Figure 7-39), similar to the behaviorobserved at L4P51-A (see Section 7.1.7.1). Therefore,a zero-flow condition was used for the externalboundary of the model during the S1 P71-A simulations.The distance to this boundary was one of theparameters fitted during test interpretation.86


SlP71-ATEST - TOOL CONFIGURATIONBOREHOLE: Sl P71TEST TOOL: #2DATE: 11/11/88DEPTH OF HOLE: 4.555 m.BOREHOLESTRATIGRAPHYO.On---~"'-~~'-M-A-P-U-N-IT~O~~~~~~~~~-1- COARSE. COLORLESS HALITE, MINORINTERCRYSTALLINE BROWN CLAYGUARD -ZONEPACKER# 30414-1124*-~wZoNIo 0::


-0- TestZone-0- Guard Zone1.5m-0- 1.0~-~::JIf)If) 0.5~0-Test S1P71 - A, Room 7, Waste Panel #1Test Zone 3.12 - 4.56 m, Vertically DownArgillaceous Halite Including Clay D0.0Time (1988 Calendar Days)TRI-6344-589-0Figure 7-39.Test- and Guard-Zone Fluid-Pressure Data from S1P71-A Testing.Even though the test-zone compressibilities calculatedfrom the first and second pUlse-withdrawal datawere high (2.89 x10- 8 Pa- 1 and 5.31 x10- 8 Pa- 1 , Table 6­3), the pressure buildup following the initial shut indisplayed the ideal decreasing-rate behavior shown inFigure 4-6. Therefore, the initial buildup period wassimulated along with the pulse-withdrawal tests, ratherthan being included as a period of specified-pressurehistory.Figure 7-40 shows the best-fit model simulation of theS1 P71-A pulse-withdrawal tests along with the observedfluid-pressure data from the test zone. Thedata from the time of penetration of the midpoint of thetest zone by drilling to the shut in for the initial bUildupperiod were included as specified-pressure history, aswere the data collected during the first minutes followingthe pulse withdrawals. The buildup period and twopulse-withdrawal tests were simulated using a specifiedformation thickness of 1.44 m, a specific storageof 1.5x10- 7 m 1 , and a test-zone compressibility of 3.92x 10- 8 Pa- 1 • The fitted parameters were a hydraulicconductivity of 4.0 x 10- 13 mls (permeability of 5 x 10- 20m 2 ), a formation pore pressure of 2.95 MPa, and adistance to the zero-flow boundary of 2.8 m. Additionalsimulations showing the sensitivity of the best-fit modelto slight changes in hydraulic conductivity, formationpore pressure, specific storage, test-zone compressibility,and distance to the zero-flow boundary, as wellas to the presence or absence of test-zone-volumecompensations, are presented in Section 7.2.7.1.9.2 Guard Zone. No pressure buildup wasobserved in the S1 P71-A guard zone following shut-in; thezone remained at atmospheric pressure throughout thetesting period inthetestzone (Figure 7-39). Pulse-injectiontests were attempted in the guard zone in S1 P71 on twoseparate occasions. Thefirst testwas attempted on May 3,1989 (1988 Calendar Day 489) at the end of the testingperiod in the test zone. The second test was attempted on88


1.5oData- SimulationTest S1 P71-A,Room 7, Waste Panel #1Test Zone 3.12 - 4.56 m, Vertically Down--c-e-e-E~o1E\ Argillaceous Halite Induding Clay 0Q)....:::JenenQ)....a..1.00.50.0)-Historyo K ~ 4.0 X 10- 13 mls (k ~ 5 x10- 20 m9Ss ~ 1.5x10- 7 m- 1p. ~ 2.95 MPaC tz~ 3.92 x 10- 8 Pa- 1:J- HistoryZero-Flow Boundary at r ~ 2.8 m....,,-.jr------------simulation-----------1.....History-0.5 L..L...................I......L.................--'-..J-..................-'--L..L..................I......L...............~.................................L.....'-..........-'--I-I.............--'-...o 25 50 75 100 125 150 175 20010 = 1988315.5307 Time Since Hole Cored (days)TRI-6344-590-0Figure 7-40.Best-Fit Model Simulation of the Test-Zone Fluid-Pressure Response During S1 P71·ATesting.July 6, 1989(1988 Calendar Day553) afterthetesttool hadbeen removed from the borehole, leak tested, and rein-­stalled in the hole. In each case, two liters of brine wereinjected into the guard zone in an attempt to create apressure differential between the guard zone and thesurrounding rock. Netther of these tests was successfulbecause the injection pressure dissipated immediatelyupon the guard zone being shut in (Saulnier et aI., 1991).Stormont (1990a) conckJded, based on examination ofextensometer, inclinometer, and gas-flow measurements,thatvertical separations almost alwaysoccurwtthin MarkerBed 139beneath roomsthe size of Room 7in Waste Panel1. These separations resu~ in depressurization of themarkerbed and high perrneabiltties. The occurrence ofthistype of separation is consistent with our observationsduring the attempted testing of Marker Bed 139 in theS1 P71-A guard zone.7.2 Sensitivity AnalysesOur first objective in test interpretation was to definethe values of the fitted parameters (hydraulic conductivity,formation pore pressure, and, in some cases,distance to a zero-flow boundary) that combined withthe specified parameters to produce the model simulationsthat most closely matched the observed data.Our approach to this problem was to investigate amatrix of values for the fitted parameters while holdingthe specified parameters fixed, and to select the combinationof fitted parameters that SUbjectively providedthe best match to the observed data.Our second objective was to evaluate the sensitivity ofthe modeling results to the values selected for both thefitted and specified parameters. This was accomplishedby individually varying the parameters hydraulicconductivity, formation pore pressure, distance to aboundary (when relevant), specific storage (whichincludes formation porosity and compressibility as wellas brine density and compressibility), and test-zonecompressibility to show the effects that these variationshad on the simulations. No sensitivity analysiswas performed for the specified parameter test-zone89


thickness, because thickness was always known towithin a few percent, and uncertainty in this parameterresults in almost linear, inverse uncertainty in hydraulicconductivity. Additional sensitivity analyses were performedto evaluate the effects of, and need for, testzone-volumeand temperature compensations. Thesesensitivity analyses provide a measure of the uncertaintyin the fitted parameters.7.2.1 HYDRAULIC CONDUCTIVITY. The sensitivitiesof the best-fit simulations to slight changes inhydraulic conductivity are shown in Figures 7-41through 7-48. Unit changes within the order ofmagnitude of the best-fit value (e.g., changing 2.5 x10- 14 mls to 1.5 x 10- 14 mls and 3.5 x 10- 14 m/s)generally resulted in noticeably poorer fits to theobserved data, particularly for hydraulic conductivitiesless than 10- 13 m/s. In the cases of the simulationof the C2H01-A testing (Figure 7-41) and the simulationof the C2H01-C testing of Marker Bed 139(Figure 7-44), which showed the highest hydraulicconductivities of any test intervals discussed in thisreport, changes in hydraulic conductivity of abouthalf an order of magnitude are needed to degradethe matches between the simulations and the observeddata noticeably.7.2.2 FORMATION PORE PRESSURE. Thesensitivities of the best-fit simulations to 0.1-MPachanges in the formation pore pressure are shown inFigures 7-49 through 7-56. In all cases, the changesin formation pore pressure resulted in observablydifferent simulations, showing formation porepressure to be a very sensitive parameter.7.2.3 DISTANCE TO A BOUNDARY. For the simulationsof the L4P51-A and S1 P71-A tests, whichincluded zero-flow boundaries, the sensitivities of theresults to the distances to the boundaries were evaluated.Figures 7-57 and 7-58 show the effects on thesimulations of 0.1-m changes in the distance to theboundary. As might be expected, the simulations arefairly sensitive to this distance because it is one of theparameters controlling the volume of fluid containedwithin the confines of the zero-flow boundary.7.2.4 SPECIFIC STORAGE. To define appropriateranges over which to evaluate sensitivities to specificstorage, the estimated uncertainties in formation elasticmoduli and porosity and brine density and compressibilitywere used. The estimated uncertaintyranges for the drained bulk and shear moduli of thedifferent rock types tested are given in Table 6-1. Arange of 22.8 to 24.0 GPa was used for the bulkmodulus of halite solids (Carmichael, 1984). The otherestimated uncertainty ranges were 0.001 to 0.03 forhalite and anhydrite porosity, 0.20 to 0.40 forclaystoneporosity, 1.20 to 1.25 kg/L for brine density, and 2.9 x10- 10 to 3.3 x 10- 10 Pa- 1 for brine compressibility.The uncertainty range for the specific storage of halitewas calculated using end-membervalues ofthe rangespresented above in Eq. 6-2. The minimum specificstorage calculated was about 2.8 x 10- 8 m- 1 , and themaximum value was about 3.6 x 10- 7 m- 1 • While thesevalues may reasonably encompass the possible rangefor the specific storage of intact halite, they are probablytoo low to be representative of fractured halite.Walsh (1965) showed that the compressibility of rockincreases when cracking or microfracturing occurs.This effect can be quantified by comparing compressional-wavevelocities through intact and fracturedrock. Compressional-wave velocities decrease whenrocks fracture. Compressional-wave velocity is relatedto the factor agiven in Eqs. 6-1 and 6-3 by (Greenand Wang, 1990):(7-1 )90


~:::](/)(/)Q)....a..3.52.51.50.5I 0 Data ITest C2H01-A, Room C2(Test lone 2.09 - 2.92 m, Vertically Down -- SimulationArgillaceous Halite, Map Units 4 and 5((HistoryHistorySs = 9.5 X 10-8 m- 1p' = 0.50 MPaC tz= 1.21 x 10- 9 Pa- 1Formation Hydraulic Conductivities:K 1 = 6.3 X 10- 12 mls (k 1 = 9 X 10- 19 m 2 ) -- r-' KK 2 = 2.0 x 10- 11 mls (k2 = 3 x 10- 18 m 2 ) K 1K 3 = 6.3 X 10- 11 mls (k 3 = 9 x 10- 18 m 2 )k' ~1 -I" K 3K- tT""3History "r-Simulation--0.5 o 5 10 15 20 25 30to= 1988217.5464Time Since Hole Cored (days)TRI-6344-S91-0Figure 7-41.Simulation of the Test-Zone Fluid-Pressure Response During C2H01-A TestingShowing the Simulation's Sensitivity to Hydraulic Conductivity.Q)....:::](/J(/JQ)....a..4.5 .........,..-r-......,..,..........,.....,,...,............-,.......,............-,.....,-.-................,....,.....,..,,.......,........-.....,;-r-.--r-'l"'""T..,....,....,.....,-,3.52.51.50.5History {= 9.5 x 10- 8 m- 1= 3.15 MPa= 1.21 x 10- 9 Pa- 1K 1 = 1.2 X 10- 13 m/s (k 1 = 2 x 10- 20 m 2 )K 2 = 4.9 X 10- 14 m/s (k 2 = 7 X 10- 21 m 2 )K 3K 4 14 21 2 3.9 x 10- mls (k 3 = 5 X 10- m )= 2.9 x 10- 14 mls (k 4 =4 X 10- 21 m 2 )K s =11.2 x 10- 14 mls (k s = 2 x 10- 21 m 2 )K~~Test C2H01-B, Room C2Test lone 4.50 - 5.58 m, Vertically DownAr9illaceous Halite, Map Unit 0} HistoryoData- Simulation"'---History ----c~----------255075100125150175200to - 1988217.5466Time Since Hole Cored (days)TRI-6344-741-0Figure 7-42.Simulation of the Test-Zone Fluid-Pressure Response During C2H01-B TestingShowing the Simulation's Sensitivity to Hydraulic Conductivity.91


3.5oData- SimulationTest C2H01-B-GZ, Room C2Guard Zone 2.92 - 4.02 m, Vertically DownArgillaceous Halite, Map Units 0 - 42.51.50.5Ss = 9.5x10- 8 m- 1p. = 4.12 MPaCgz = 1.21 X 10. 9 Pa- 1Formation Hydraulic Conductivities:K 1 = 4.4 X 10- 14 mls (k 1 = 6 X 10- 21 m 2 )K 2 = 2.4 x 10- 14 m/s (k 2 = 3 X 10- 21 m 2 )K 3 = 1.4 X 10- 14 mls (k 3 = 2 x 10- 21 m 2 )K 4 = 9.4 x 10- 15 mls (k 4 = 1 X 10- 21 m 2 )K 5 = 4.4 x 10- 15 mls (k 5 = 6 x 10- 22 m 2 )1-----History ----~..~If--------Simulation --------..-0.5 l...I.......................L......................&-J...,.,.......................L....L.-............&-.L...L...............--L....&-.................L...L-'-...L.-L....L....&-............&......Io 25 50 75 100 125 150 175 200to = 1988217.4687Time Since Hole Cored (days)TRI-6344-742-0Figure 7-43.Simulation of the Guard-Zone Fluid-Pressure Response During C2H01-B TestingShowing the Simulation's Sensitivity to Hydraulic Conductivity.9 .............~T"""I".,..,,...,...T"""I".......,,.....,.."T'""T....,... .............~,....,..,..,~.......,..,,.....,.."T'""T....,...,.....,..............,...,....,..,..,~.............,...,7oData- Simulation~- 2?::J'@"0..(J)(J)Q)....0..5 History3} HistoryTest C2H01-C, Room C2Test Zone 6.63 - 8.97 m, Vertically DownSimulation Thickness 0.96 m, Marker Bed 139Ss = 1.4 x 10- 7 m- 1p. = 8.05MPaC tz= 3.02 x 10- 9 Pa- 1Formation Hydraulic Conductivities:K, 2.2 x 10- 11 mls (k, 3 x 10- 18 m 2 )K 2 = 7.0 x 10- 12 m/s (k 2 = 1 X 10- 18 m 2 )K 3 = 2.2 x 10- 12 m/s (k 3 = 3 x 10- 19 m 2 )---'*"----------- Simulation-------........102030405060708090100to - 198944.4479Time Since Hole Cored (days)TRI-6344-594-0Figure 7-44.Simulation of the Test-Zone Fluid-Pressure Response During C2H01-C TestingShowing the Simulation's Sensitivity to HydraUlic Conductivity.92


9.5 ,...............,...,r'"""""".,....,..,..,.....................-r....,..,......"I'"T"'T'"'l.............."T'""O.......-.,............,..,,....,....,....,."'T'"'l,................."'T"".............,7.5Test C2H02, Room C2Borehole Oriented 45° Downward from HorizontalTest Zone 9.47 - 10.86 m, Marker Bed 139Simulated Vertical Thickness 0.86 mo DataC? - Simulationa..~ 5.5-Q)....::Jenen~ 3.5a..1.5::r HistorySs = 1.4xl0- 7 m- 1p' = 9.30 MPaCtz = 9.87 X 10- 9 Pa- 1Formation Hydraulic Conductivities:K 1 = 6.7 x 10. 13 rnIs (k 1 = 9 x 10- 20 m 2 )K 2 = 5.7 x 10- 13 m/s (k 2 = 8 x 10- 20 m 2 )K 3 = 4.7 x 10- 13 rnIs (k 3 = 6 x 10- 20 m 2 )Simulation255075100125150175200225250to ~ 1989107.3905 Time Since Hole Cored (days)TRI-6344-595-oFigure 7-45.Simulation of the Test-Zone Fluid-Pressure Response During C2H02 Testing Showingthe Simulation's Sensitivity to Hydraulic Conductivity.2.5 ...."T'""O.......-,...............,...,r'"""""".,....,..,..,.....................-r....,..,......'J":'T"'T'"'l.............."T'""O.......-.,............,..,.,..,....,."'T'"'l-r-......."T'""O-,'K 11.5TestL4P51-A, Room L4 0 DataTest Zone 3.33 - 4.75 m, Vertically Down _ SimulationArgillaceous Halite Including Clay DQ)....::Jenen~a..0.5~ } HistoryHistorySs = 1.3 x 10- 7 m- 1p' = 2.75 MPaCtz = 7.16 x 10- 10 Pa- 1Formation Hydraulic Conductivities:K 1 = 5_5 X 10- 14 rnIs (k 1 =7 x 10- 21 m 2 )K 2 = 4.5 x 10- 14 rnIs (~= 6 x 10- 21 m 2 )K 3 = 3.5 X 10- 14 m/s (k 3 = 5 x 10- 21 m 2 )Zero-Flow Boundary at r = 2.0 mHistory--1-------------Simulation ----------I~~-0.5 ....L..J,...L.-' .L...L. ....L..J, ............o255075to ~ 1989 291.5859 Time Since Hole Cored (days)100125150 175 200 225 250TR 1-6344-596-0Figure 7-46.Simulation of the Test-Zone Fluid-Pressure Response During L4P51-A TestingShowing the Simulation's Sensitivity to Hydraulic Conductivity.93


TestSOPOl3.5 South 1300 Drift, Easl of E140 DriftTest Zone 3.74 - 5.17 m, Vertically DownArgillaceous Halite Including Clay DCi3 2.5a..~oData- Simulation0.5255075100Ss = 1.1 X 10- 7 m- 1p' = 4.45 MPaC 1z= 1.7 X 10- 8 Pa- lFormation Hydraulic Conductivities:125K, = 7_1 X 10- 14 m/s (k, = 1 X 10- 20 m- 2 )K 2 = 6.1 X 10- 14 m/s (k 2 = 8 X 10- 21 m·2)K 3= 5.1 X 10- 14 mls (k 3= 7 X 10- 21 m- 2 )1Tlli'f---------------Simulation------------........-0.5 L.l. ...L.. -I.. -I.. -I.. L..-I- .......oto - 1989 11.59357150Time Since Hole Cored (days)175200225TRI-6344-597-DFigure 7-47.Simulation of the Test-Zone Fluid-Pressure Response During SOP01 Testing Showingthe Simulation'S sensitivity to Hydraulic Conductivity.1.5Ci3a.. 1.0~....


4.53.5I 0 Data ITest C2H01-A, Room C2- SimulationTest Zone 2.09 - 2.92 m. Vertically DownArgillaceous Halite, Map Units 4 and 5I,C?a.. 2.5::2:-Q).....:J lJ)lJ)Q).....a..1.50.5K = 2.0 x 10- 11 mls (k = 3 x 10- 18 m 2 )Ss = 9.5 x 10-8 m- 1Ctz = 1.21 x 10-9 Pa- 1Formation Pressure:History- IIpi= 0.6 MPa - 1--pi = 0.5 MPap; = 0.4 MPa~ /pi'-p;"'""History Simulation -~History-0.5o 5 10 15 20 25 30to - 1988 217.5464Time Since Hole Cored (days)TRI-6344-59S-0Figure 7-49.Simulation of the Test-Zone Fluid-Pressure Response During C2H01-A TestingShowing the Simulation's Sensitivity to Formation Pore Pressure.3.5History {Test C2H01-B, Room C2Test Zone 4.50 - 5.58 m. Vertically DownArgillaceous Halite, Map Unit 0C?a.. 2.5::2:-Q).....:J lJ)lJ) 1.5Q).....a..J- HistoryK = 3.9 X 10- 14 m/s (k = 5 x 10- 21 m 2 )5 s = 9.5 X 10- 8 m- 1C tz = 1.21 x 10- 9 Pa- 1Formation Pressure:0.5pi = 3.25 MPapi = 3.15 MPap; = 3.05 MPaHistory ----i..~----'=---------5imulation---------I..~I-0.50 25 50 75 100 125 150 175to = 1988 217.5466Time Since Hole Cored (days)200TRI-6344-600-0Figure 7-50.Simulation of the Test-Zone Fluid-Pressure Response During C2H01-B TestingShowing the Simulation's Sensitivity to Formation Pore Pressure.95


3.5Test C2H01-B GZ, Room C2Guard Zone 2.92 - 4.02 m, Vertically DownArgillaceous Halite, Map Units 0 - 4pi2.51.50.5K = 1.4 X 10- 14 mls (k = 2 x 10- 21 m 2 )Ss = 9.5 X 10- 8 m- lC gz = 1.21 X 10- 9 Pa- lFormation Pressure:p; = 4.22 MPaP2 = 4.12 MPap; = 4.02 MPa1----- History -------,)..~I--------Simulation----------c...~-0.5 L...I.-'--'-.a......J-'- ~ ..L- -'-.a......J-'- ~ -'- .......25 50 75 100 125 150 175 200oto - 1988 217.4687Time Since Hole Cored (days)TRI-6344-601-0Figure 7-51.Simulation of the Guard-Zone Fluid-Pressure Response During C2H01-B TestingShowing the Simulation's Sensitivity to Formation Pore Pressure.7.0oData- Simulation~-~a.. 5.0~:::llJ)lJ) 3.0~a..1.0} HistoryTest C2H01-C, Room C2Test Zone 6.63 - 8.97 m, Vertically DownSimulation Thickness 0.96 m, Marker Bed 139K = 7.0 X 10- 12 mls (k = 1 x 10- 18 m 2 )Sg = 1.4 x 10- 7 m- lC lz = 3.02 x 10- 9 Pa- lFormation Pressure:pi = 8.15 MPaP2 = 8.05 MPaP; = 7.95 MPa---..I---------simulation---------..;..~102030405060708090100to - 198944.4479Time Since Hole Cored (days)TRI-6344-602-0Figure 7-52.Simulation ofthe Test-Zone Fluid-Pressure Response During C2H01-C TestingShowing the Simulation's Sensitivity to Formation Pore Pressure.96


9.0 Test C2H02, Room C2Borehole Oriented 45° Downward from HorizontalTest Zone 9.47 - 10.86 m, Marker Bed 139Simulated Vertical Thickness 0.86 m7.0"@'n.6. 5.0~ :::JUlUlQ) 3.0et1.0oData- SimulationK = 5.7 x 10. 13 mls (k = 8 x 10. 20 m 2 )Ss = 1.4 x 10- 7 m·1C tz = 9.87 X 10. 9 Pa- 1Formation Pressurepi = 9.40 MPa~ = 9.30MPaP3 = 9.20 MPat-='--------- History ------I-------Simulation----1_..-1.0 L.J................................................L..J.....L...J~..1....L_'_..........L..&.....................L..I................................................L-.........................................."'""'_.............L...JL_I2575 100150 175 200ato - 1989 107.390550125Time Since Hole Cored (days)225250TR1-6344-603-0Figure 7·53.Simulation of the Test-Zone Fluid-Pressure Response During C2H02 Testing Showingthe Simulation's Sensitivity to Formation Pore Pressure."@' 1.5n.::2~ :::JUlUlQ)~n. 0.5~ }HistOryHistoryTest L4P51·A. Room L4Test Zone 3.33 - 4.75 m, Vertically DownArgillaceous Halite Induding Clay DK = 4.5 X 10. 14 mfs (k = 6 x 10- 21 m 2 )Ss = 1.3x10·7 m- 1C tz = 7.16 X 10- 10 Pa- 1Formation Pressure:pi= 2.85 MPapi = 2.75 MPap; = 2.65 MPaZero-Flow Boundary at r = 2.0 moData- SimulationHistory ---+---------SimUlation------------1_..-0.5 ..L-l_ ....L-L....L-L....L-L ....a255075to - 1989291.5859Time Since Hole Cored (days)100125150175200225250TRI-6344-604-0Figure 7-54.Simulation of thl~ Test-Zone Fluid·Pressure Response During L4P51-A TestingShowing the Simulation's Sensitivity to Formation Pore Pressure.97


4.5 r-r..............-r-.............."""T'""'T'"""r-r-.,......,-r-T"""T-r-T""""......,...,.."'T""'........,...,r-r'........-r-...,.-r-..........,...,........,...,...,..,3.5oData- SimulationTest SOPOlSouth 1300 Drift, East of E140 DriftTest Zone 3.74 - 5.17 m, Vertically DownArgillaceous Halite Including Clay DCil~ 2.5~ ::J(/)~ 1.50:0.5K = 6.1 X 10- 14 mls (k = 8 x 10. 21 m 2 )Ss = 1.1 X 10- 7 m·1c'z = 1.7 x10- 8 Pa- 1Formation Pressure:P"l = 4.55 MPaP"2 = 4.45 MPaP"3 = 4.35 MPa1-ocJ1if--------------Simulation--------------t~~-0.5 L...L. L.:L ..I.....I. ..I.....I. ..L..L ....&...l L...L. L...L. L...L. ......o2550to - 1989 11.59357Time Since Hole Cored (days)75100125150175200225TRI-6344-605-0Figure 7-55.Simulation of the Test-Zone Fluid-Pressure Response During SOP01 Testing Showingthe Simulation's Sensitivity to Fonnation Pore Pressure.2.0 ~..,..."'T"""......,..,..."'T""".,.....,.....,..-.--.,.....,.............."T"'""I'"""T.......,..-........,..."'T""".,.....,..,...-.--.,......,................"T"'""F""'T......"'T"""I'"""T....,1.5pi"oData- SimulationCil0- 1.0~~ ::J(/)(/)0.5Q)...0-0.0}- HistoryK = 4.0 x 10- 13 mls (k = 5 x 10- 20 m 2 )S5 = 1.5 x 10- 7 m- 1C tz = 3.92 X 10- 8 Pa·1Formation Pressure:pi = 3.05 MPaP2 = 2.95 MPaP3= 2.85 MPa::J- HistoryTest Sl P71-ARoom 7, Waste Panel #1Test Zone 3.12 - 4.56 m, Vertically DownArgillaceous Halite Including Clay DZero-Flow Boundary at r = 2.8 m........,......ot-------------Simulation-------------~History-0.50 25507510012515017520010-1988315.5307Time Since Hole Cored (days)TR1-6344-606-0Figure 7-56.Simulation of the Test-Zone Fluid-Pressure Response During S1 P71-A TestingShowing the Simulation's Sensitivity to Formation Pore Pressure.98


3.0 .-....-"""T""---r---,r---r-....,...-..----,r-.---....-"""T""--,-.---..---.....--r--.-.---....---r---r-.---...---,2.52.0'@'a..~ 1.5-Q)~::l(/) 1.0(/)Q)~a..0.50.0~ }HistOryHistoryTest L4P51-A, Room L4r1Test Zone 3.33 - 4.75 m, Vertically DownArgillaceous Halite Including Clay 0K = 4.5 X 10. 14 m/s (k = 6 x 10- 21 m 2 )Ss = 1.3 X 10. 7 m- 1p' = 2.75MPaCt, = 7.16 X 10- 10 Pa- 1Zero-Flow Boundary:r 1= 1.9mr 2= 2.0 mr 3= 2.1 mHistory --.jl-----------Simulation-----------1....-0.5 '---'-.......----'_L.-........--L---''--.................---L_'---'-......----'_"''--........--L---''--...............---L_L.-..........4080120160200240oto =1989291.5859Time Since Hole Cored (days)TR1-6344-607-0Figure 7-57.Simulation of the Test-Zone Fluid-Pressure Response During L4P51-A TestingShowing the Simulation's Sensitivity to Distance to the Zero-Flow Boundary.2.0oData- SimulationRoom 7, Waste Panel #1Test Zone 3.12 - 4.56 m, Vertically DownArgillaceous Halite Including Clay 0~-"@" 1.5a..1.00.50.0History -[= 4.0 x 10- 13 m/s (k = 5 x 10. 20 m 2 )= 1.5xlO- 7 m- 1= 2.95 MPaCtz = 3.92 x 10- 8 Pa- 1Zero-Flow Boundary:r 1= 2.9 mr 2 = 2.8 mr 3= 2.7 m~-+--------------Simulation-----------1....-0.5 L.....L..................~...............'_'_...l................_'__.L.....L.........._'__I._..l-'-........'-'-...l..................-'-.L.....L.........._'__.I......l.............................Jo 25 50 75 100 125 150 175 200to = 1988315.5307Time Since Hole Cored (days)TRI-6344-608-0Figure 7-58.Simulation of the Test-Zone Fluid-Pressure Response During S1 P71-A TestingShowing the Simulation's Sensitivity to Distance to the Zero-Flow Boundary.99


where:V ::: pcompressional-wave veloctty0. uniaxial compressibility given by Eq. 6-3P rock densityBrodsky (1990) reported decreases in compressionalwavevelocities in the laboratory of up to eleven percentin Salado halije specimens at one percent axialstrain. Ibrahim et al. (1989) reported in situ decreasesin compressional-wave velocities of up to about 50percent within about 1.5 mofWIPPexcavations. A50­percent decrease in V pin Eq. 7-1 translates to afourfold increase in 0.. Thus, specific storage mightalso increase by about this factor as a result ofmicrofracturing around the WIPP excavations. Accordingly,the maximum value of specific storage ofhalite considered in the sensitivity calculations was1.4 x 10- 6 m- 1 •The uncertainty range for the specific storage ofanhydrite was calculated using end-member valuesof the ranges presented above in Eq. 6-1. Specificstorage was calculated to range from a low of about9.7 x 10- 8 m- 1 to a high of about 2.5 x 10- 7 mol. Toaccount for the effects of fracturing on anhydritecompressibility, the maximum value of specific storageto be considered in sensitivity calculations wasincreased to 1.0 x 10- 6 mol.The uncertainty range for the specific storage ofclaystone was calculated using end-membervalues ofthe ranges presented above in Eq. 6-1. Specificstorage was calculated to range from a low of about 1.7x 10- 6 m- 1 to a high of about 5.6 x 10- 6 m 1 •The sensitivities of the best-fit simulations to the estimateduncertainties in spec~ic storage are shown inFigures 7-59 through 7-66. In general, the simulationsare about as sensitive to the uncertainty in specificstorage as they are to the unit changes within the orderof magnttude of the best-fij value of hydraulic conductivttypresented in Figures 7-41 through 7-48, orto the0.1-MPa changes in formation pore pressure presentedin Figures 7-49 through 7-56.However, thesimulations of the L4P51-A and S1 P71-A tests (Figures7-32 and 7-40, respectively), which include zeroflowboundaries, are highly sensitive to specific storagebecause that parameter governs the amount ofbrine releasable from storage within the zero-flowboundary.To evaluate which of the fitted parameters was mostsensitive to the uncertainty in specific storage, theL4P51-A and S1 P71-A tests were resimulated to obtainthe best fit to the data using the end-membervalues of specific storage as specified parameters.The SOP01 tests were also resimulated using thelower end-member value of specific storage for comparisonpurposes.Figures 7-67 and 7-68 show the simulations thatbest matched the L4P51-A test data when specificstoragevalues of 1.5 x 10-6 m·1 and 5.2 x 10- 8 m- l ,respectively, were specified. Compared to the simulationwith the base-case value of specific storage of1.3 x 10. 7 m l (Figure 7-32), the estimated hydraulicconductivity and formation pore pressure changedonly slightly. For the high-specific-storage case(Figure 7-67), hydrau lic co nductivity decreased from4.5 x 10- 14 to 3.0 x 10- 14 mls and formation porepressure increased from 2.75 to 2.85 MPa. For thelow-specific-storage case (Figure 7-68), hydraulicconductivity decreased to 4.0 x 10- 14 m/s and formationpore pressure increased from 2.75 to 2.88 MPa.The parameter that proved to be most sensitive tospecific storage was the distance to the zero-flowboundary. For the high-specific-storage case, thedistance to the boundary decreased from 2.00 to0.52 m, while for the low-specific-storage case, itincreased to 2.65 m.100


3.5((I 0 Data I- Simulation~ 2.5a..~-Q)...::Jen...enQ)a..1.50.5Test C2H01-A, Room C2Test Zone 2.09 ' 2.92 m, Vertically DownArgillaceous Halite, Map Units 4 and 5K = 2.0 x 10- 11 mls (k =3 x 1O- 1S m 2 )p' = 0.5 MPaCtz = 1.21 x 10. 9 Pa·1HistorySpecific Storage:S1 = 2.8 x 10. 8 m- 1 - ...S2 = 9.5 x 10- 8 m- 1 - r-S3 = 1.4 X 10- 6 m- 1 ~/~~S1/~HistoryV'>'~ISimulation _HistoryI-0.5o 5 10 15 20 25 30to = 1988217.5464Time Since Hole Cored (days)TRI-6344-609-QFigure 7-59.Simulation of the Test-Zone Fluid-Pressure Response During C2H01-A TestingShowing the Simulation's Sensitivity to Specific Storage.54} HistoryS3TestC2H01-B, Room C2Test Zone 4.50·5.58 m, Vertically DownArgillaceous Halite, Map Unit 0~ 3a..6Q)...::Jenen...Q)a..20History53}- HistoryK = 3.9 X 10- 14 mls (k = 5 x 10- 21 m 2 )p' = 3.15 MPaC tz = 1.21 x 10. 9 Pa·1Specific Storage:Sl = 1.4 x 1O. 6 m,1S2 = 9.5 x 10,8 m,1~IS3 = 2.8 X10- 8 m- 1} History-10 255075100125150175200to - 1988217.5466Time Since Hole Cored (days)TRI-6344-610-0Figure 7-60.Simulation of the Test-Zone Fluid-Pressure Response During C2H01-B TestingShowing the Simulation's Sensitivity to Specific Storage.101


3.5oData- SimulationTest C2H01-B GZ, Room C2Guard Zone 2.92 - 4.02 m, Vertically DownArgillaceous Halite, Map Units 0 - 42.51.50.575K = 1.4 X 10- 14 mls (k = 2 x 10- 21 m 2 )p' = 4.12 MPaC gz= 1.21 X 10- 9 Pa- 1Specific Storage:S1 = 1.4xlO- 6 m- 1S2 = 9.5 x 10- 8 m- 1S3 = 2.8 x 10- 8 m- 1t----- History -----1..~If---------0.5 .......--I......................................L....L..........a.-.................a.-................................--I..........................................'-'-.........a.-.....................................25 50100 125 150 175 200oto - 1988 217.4687Time Since Hole Cored (days)..TRI-6344-611-0Figure 7-61.Simulation ofthe Guard-Zone Fluid-Pressure Response during C2H01-B TestingShowing the Simulation's Sensitivity to Specific Storage.~ ::J(/)(/)~ 3a.History {} HistoryTest C2H01-C, Room C2Test Zone 6.63 - 8.97 m, Vertically DownSimulated Thickness 0.96 m, Marker Bed 139K = 7.0 x 10- 12 m/s (k = 1 x 10- 18 m 2 )p' = 8.05 MPaC tz = 3.02 X 10- 9 Pa- 1Specific Storage:S1 = 1.0 X 10- 6 m- 1S2 = 1.4 x 10-4 m-1S3 = 9.7 X 10- 8 m- 1 100----i.....II----------Simulation--------.......-1 '----I._..a.---'_........_'---'-_-'--........_-'----'I---'-_.l.-........_ ......---'I--......._.l...-........_ ......---Ioto = 198944.44792040Time Since Hole Cored (days)6080TRI-6344-612-0Figure 7-62.Simulation of the Test-Zone Fluid-Pressure Response during C2H01-C TestingShowing the Simulation's Sensitivity to Specific Storage.102


97Test C2H02, Room C2Borehole Oriented 45° Downward from HorizontalTest Zone 9.47 - 10.86 m, Marker Bed 139Simulated Thickness 0.86 moData- SimulationJ- HistoryK = 5.7 x 10- 13 mls (k = 8 x 10. 20 m 2 )p. = 9.30 MPaCtz = 9.87 x 10- 9 Pa- lSpecific Storage:SI = 1.0 x 10-6 m- l~ = 1.4 x 10- 7 m- lS3 = 9.7 x 10- 8 m- l1-==-------History-------..~+I-----Simulation-----.. ~-1 J....L....L...J ...L...& J....L....L...J J....L....L...J ......oto = 1989 107.3905255075100125150Time Since Hole Cored (days)175200225250TRI-6344-613-0Figure 7-63.Simulation of the Test-Zone Fluid-Pressure Response During C2H02 Testing Showingthe Simulation'S Sensitivity to Specific Storage.2.5oData- Simulationca-D..~ 1.5....


Test SOP013.5 South 1300 Drift, East of E140 DriftTest Zone 3.74 - 5.17 m, Vertically DownPolyhalitic Halite Induding Clay D2.5'@'a..~-~1.5:::JenenQ)...a..0.5oData- Simulation255075100125K = 6.1 X 10- 14 m/s (k = 8 x 10- 21 m 2 )p. = 4.45 MPaC tz =1.7x10- 8 pa- 1Specific Storage:S1 = 1.4XlO- 6 m- 1S2 = 1.1 X 10- 7 m- 1S3 = 4.0x 10- 8 m- 1~*"-------------Simulation -------------.-;.......-0.5 L..L ..J- L-L. i-L....L- -'- .....oto = 1989 11.59375150Time Since Hole Cored (days)175200225TR 1-6344-615-0Figure 7-65.Simulation of the Test-Zone Fluid-Pressure Response During SOP01 Testing Showingthe Simulation's Sensitivity to Specific Storage.Test S1 P71-A, Room 7, Waste Panel #1Test Zone 3_12 - 4.56 m, Vertically Down2.5 Argillaceous Halite Induding Clay D'@'a.....:::Jenen...Q)~-Q) 1.5a..History0.5K = 4.0 X 10- 13 m/s (k = 5 x 10- 20 m 2 ) Specific Storage:p. = 2.95 MPaS1 = 1.5x10- 6 m- 1C tz= 3.92 X 10- 8 Pa- 152 = 1.5xlO- 7 m- 153 = 6_3 x 10- 8 m- 1Zero-Flow Boundary at r = 2.8 m!--'~+------------- Simulation-------------..,.....History-0.5 .....--L...........:;.,............--L-'-...I-.L-.............-L..........L-........-..1.-'--'-.L-......--L......................I......L.....................&....o........................o 25 50 75 100 125 150 175 200to - 1988315.5307Time Since Hole Cored (days)TR 1-6344-616-0Figure 7-66. Simulation of the Test-Zone Fluid-Pressure Response During S1 P71-A TestingShowing the Simulation's Sensitivity to Specific Storage.104


2.52.0OwoData- Simulation(? 1.50-::2-(1)1.0~::Jenen(1)~0-0.50.0Test L4P51·A. Room L4Test Zone 3.33 - 4.75 m, Vertically DownArgillaceous Halite Including Clay DK = 3.0 x 10- t4 mls (k = 4 x 10- 21 m 2 )Ss = 1.5 x 10-6 m- 1p. = 2.85 MPaCtz = 7.16 X 10- 10 Pa- 1Zero-Flow Boundary at r = 0.52 mHistory --+jf-----------Simulation---------....-0.5a 25 5075100125150175200225250to = 1989 291.5859Time Since Hole Cored (days)TRI-6344-617-0Figure 7-67. Best-Fit Model Simulation of the Test-Zone Fluid-Pressure Response During L4P51-ATesting Using the Maximum Estimated Value for Specific Storage.2.5oData- SimulationTest L4P51-A. Room L4Test Zone 3.33 - 4.75 m. Vertically DownArgillaceous Halite Including Clay D(?0-::2 1.5-(1)~::Jen(J)(1)~0-0.5~ } HistoryHistoryK = 4.0 X 10- 14 mls (k = 5 x 10- 21 m 2 )5 s = 5.2 X 10-8 m- 1p. = 2.88 MPaC tz = 7.16 x 10. 10 Pa- 1Zero-Flow Boundary at r = 2.65 mHistory --i"~It----------Simulation --------------1~~-0.5 L-J...........~.........................L..................I_J............................._'_.........o....JL...&,.................J.....L_'_.......~....................L_..............o....L_'_.............,ato - 1989 291.5859255075100 125 150 175 200 225 250Time Since Hole Cored (days)TRI-6344-61B-0Figure 7-68. Best-Fit Model Simulation of the Test-Zone Fluid-Pressure Response During L4P51-ATesting Using the Minimum Estimated Value for Specific Storage.105


Figure 7-69 shows the simulation that best matchedthe S1 P71-A test data when specific storage wasdecreased from its base-case value of 1.5 x 10- 7 m- 1 to6.3 x 10-8 m- 1 • The estimated hydraulic conductivitydecreased slightly from 4.0 x 10- 13 to 3.1 x 10- 13 mis,and formation pore pressure increased from 2.95 to3.50 MPa. The distance to the zero-flow boundarychanged by a greater percentage, increasing from2.80t03.57 m. No simulation ofthe S1 P71-Atestdatausing a specific storage of 4.7 x 10- 7 m- 1 is shownbecause a simulation using an even more extremevalue is presented below.Figure 7-70 shows the simulation that best matchedthe SOP01 test data when specific storage was decreasedto 4.0 x 10- 8 m- 1 from its base-case value of1.1 x 10- 7 m- 1 • Compared to the base-case simulation(Figure 7-35), hydraulic conductivity increased from6.1 x 10- 14 to 6.6 x 10- 14 mis, while formation porepressure was unchanged. Figure 7-71 shows thattheradius of influence of the testing increased as a resultof the decrease in specific storage, when comparedwith the base-case radial pressures shown inFigure 7-36.McTigue et al. (1989) have suggested that the effectsof deformation and creep might result in anapparent specific storage as much as three orders ofmagnitude greaterthan a specific storage calculatedusing Eqs. 6-1 or 6-2. Accordingly, attempts weremade to fit the responses observed du ri ng the SO PO1and S1 P71-A testing using a capacitance (Ss/p,g) of3.4 x 10 9 Pa- 1 (McTigue, 1989), which produces aspecific-storage value of about 4.1 x 10- 5 m- 1 .base-case value of specific storage of 1.1 x 10- 7 m- 1(Figure 7-35). As a result of increasing the specificstorage by over two orders of magnitude, the calculatedradius of influence of the SOP01 testing decreasedsignificantly. Figure 7-73 shows that theradius of influence of the entire SOP01 testing sequenceassuming high specific storage was only about20 cm, or only about 15 cm past the wall of theborehole, compared to a radius of influence of over 8m using the base-case value of specific storage (Figure7-36). The effects of the individual pulses are onlyobserved out to a radial distance of about 9 em, about4 cm past the wall of the borehole. This result is notsurprising, because the pressure distribution in a porousmedium is controlled by the hydraulic diffusivity(KISs). Between the base-ease simulation and thehigh-specific-storage simulation, the SOP01 hydraulicdiffusivity decreased from 5.5 x 10- 7 m 2 /s to 1.5 x10·1°m2/s.The best fit obtained to the S1 P71-A data using thehigh specific-storage value of 4.1 x 10- 5 m- 1 (Figure 7­74) matched the data almost as well as the basecasesimulation, which used a specific storage of 1.5x 10- 7 m- 1 (Figure 7-40). Relative to the base-casesimulation, hydraulic conductivity was decreasedfrom 4.0 x 10- 13 to 9.0 x 10- 14 mis, formation porepressure was increased from 2.95 to 3.50 MPa, andthe distance to the zero-flow boundary was decreasedfrom 2.80 to 0.115 m for the high-specific-storagesimulation. A distance of 0.115 m to the zero-flowboundary implies that only an annulus of rock aroundthe borehole about 6 cm thick contributed to theobserved response.A good match was obtained to the SOP01 data (Figure7-72) by decreasing the hydraulic conductivityfrom 6.1 x 10- 14 to 6.0 x 10- 15 mis, and increasing theformation pore pressure from 4.45 to 6.40 MPa, relativeto the best-fit simulation that employed theThe physical processes that may contribute to specificstorage in halite are uncertain. However, we can drawconclusions from the SOP01 simulations with low andhigh values of specifiC storage (Figures 7-70 and 7-72,respectively) as to how uncertainty in specific storage106


n-~ 1.0~ ::len~ 0.5.....a..0.0K = 3.1 X 10- 13 nvs (k = 4 X 10. 20 m 2 )S5 = 6.3 X 10. 8 m- 1p' = 3.50 MPaC tz = 3.92 X 10- 8 Pa·1Zero-Flow Boundary at r = 3.57 m:J- HistoryTestS1P71-A, Room 7, Waste Panel #1Test Zone 3.12 - 4.56 m, Vertically DownArgillaceous Halite Including Clay DI-~ol-------------- Simulation --------------'~~-0.5 1..-J.__'_~.a.......J__'_........"'__J...........................L....L_L..~.L._&~...J.... ........__'_........"'__J........................'_&.~~........__'_.........L._&__'oto - 1988 315.5307255075100125Time Since Hole Cored (days)150175200TRI-6344-619-0Figure 7-69. Best-Fit Model Simulation of the Test-Zone Fluid-Pressure Response During S1 P71-ATesting Using the Minimum Estimated Value for Specific Storage.4.53.5rna..::2: 2.50.50 Data- SimulationCD 0 8.....::l~oenen0 0..... CD 1.5a.. 0 6>0Test SOP01, South 1300 Drift, East of E140 DriftTest Zone 3.74 - 5.17 m, Vertically DownPolyhalitic Halite Including Clay DK = 6.6 X 10- 14 mls (k = 9 X 10- 21 m 2 )S5 = 4.0 X 10- 8 m- 1p' = 4.45 MPac'z = 1.7 X 10-8 Pa- 1'HistOrY.-0.5 L....>............L...:L-...L-....................-.L...................L..J...........................L...L.....L-..........1......................L...L.............--'-.L..J............................L....I....................Io 25 50 75 100 125 150 175 200 225to - 1989 11.59375Time Since Hole Cored (days)TRI-6344-620-0Figure 7-70. Best-Fit Model Simulation of the Test-Zone Fluid-Pressure Response During SOP01Testing Using the Minimum Estimated Value for Specific Storage.107


4.2C?0-~Q)...::::lenenQ)...0-3.83.43.025 50 75 100 125 150 17510.198911.59357 Time Since Hole Cored (days)-e-- R = 12.0 m--e- R = 6.0 m-6- R= 3.0m-+- R= 1.0m-*- R= 0.5 m200 225TRI-6344-621-0Figure 7-71. Simulated Formation Pore Pressures at Selected Radial Distances from the Test ZoneDuring SOP01 Testing Using the Minimum Estimated Value for Specific Storage.3.5oData- SimulationTest SOP01, South 1300 Drift, East of E140 DriftTest Zone 3.74 - 5.17 m. Vertically DownPolyhalitic Halite Including Clay DC? 2.50-~~~ 1.5...enQ)0-0.5K = 6.0x10- 15 mfs(k=8x10- 22 m 2 )S. = 4.1 x 10- 5 m- 1p' = 6.40 MPaC lz= 1.7 x 10- 8 Pa- 1h:l''"t-----------Simulation ---------------i~~-0.5 L..L ~ "'__" ...L..& ....I...JL--L.....L- &....I. .....a255075100125 15010.198911.59375 Time Since Hole Cored (days)175200 225TRI-6344-622·0Figure 7-72. Best-Fit Model Simulation of the Test-Zone Fluid-Pressure Response During SOP01Testing Using a Specific Storage of 4.1 x 10- 5 M-1.108


6'@'a..5~(1)....::JlJ)lJ)(1)....a..43-&- R =0.20m-e- R=0.12m-*- R =O.09m-+- R = 0.07 m"'* R =0.06 mto - 1989 11.59357Time Since Hole Cored (days)TRI-6344-623-0Figure 7-73. Simulated Formation Pore Pressures at Selected Radial Distances from the Test ZoneDuring SOP01 Testing Using a Specific Storage of 4.1 x 10- 5 M-1.1.5oData- SimulationTest S1 P71-A, Room 7, Waste Panel #1Test Zone 3.12 - 4.56 m, Vertically DownArgillaceous Halite Including Clay D_~~&-1~'@'a.1.0~(1)....::JlJ)lJ)(1)....a.0.5K = 9.0 x 10- 14 mls (k = 1 x 10- 20 m 2 )Ss = 4.1 X 10- 5 m- 1p' = 3.50 MPaC ll = 3.92 x 10- 8 Pa- 1::r History0.0Zero-Flow Boundary at r = 0.115 mI'--:_f----------- Simulation-------------1....-0.5 L.....L..........~L_L................'__'_...I_.........__'_.........L....L..................L_L.................__'_...I_.........................L....L.........................................__'_....Ja2550to - 1988 315.5307Time Since Hole Cored (days)75100 125 150 175 200TRI-6344-624-0Figure 7·74. Best·Fit Model Simulation of the Test·Zone Fluid·Pressure Response During SlP71·ATesting Using a Specific Storage of 4.1 x 10- 5 M-1.109


affects estimates of other parameters. With respect tobase-case values of specific storage, which assumepore deformation is caused only by changes in verticaleffective stress, the inclusion of other mechanisms ofpore deformation that increase specific storage willserve to decrease estimates of hydraulic conductivityand increase estimates of formation pore pressure.Inclusion of factors that decrease specific storage willincrease estimates of hydraulic conductivity and decreaseestimates of formation pore pressure. In thecase of the SOP01 simulations, varying specific storageover three orders of magnitude caused best-fithydraulic-conductivity values to vary over only oneorder of magnitude. In the case of simulations involvingzero-flow boundaries, however, the effects ofchanges in specific storage on hydraulic conductivityand formation pore pressure are more difficult topredict because of the added influence of the boundary.In all cases, estimates of radii of influence ordistances to zero-flow boundaries decrease as specificstorage increases, because the volume of rockaffected by a test is roughly inversely proportional tohydraulic diffusivity.7.2.5 TEST-ZONE COMPRESSIBILITY. A valuefortest-zone compressibility was calculated for eachpulse withdrawal except for the first one during theC2H01-B testing (Table 6-3). The base-case valueused in the simulations of a particular testing sequencewas the log-average of all available valuesfrom that testing sequence. Figures 7-75 through7-82 show the sensitivities ofthe best-fit simulationsto the values of test-zone compressibility calculatedfrom the individual pulse-withdrawal data. Whenonly one value of test-zone compressibility wasavailable for a particular testing sequence, as forC2H01-B, the sensitivity calculations were performedusing values of test-zone compressibility about halfan order of magnitude higher and lower than thesingle calculated value. Also, because no values oftest-zone compressibility were available for theC2H01-A and C2H01-B-GZ sequences, sensitivityto test-zone compressibility for these sequenceswas evaluated using the same range of values aswas used for the C2H01-B testing sequence.Changing test-zone compressibility by half an orderof magnitude for the C2H01-A, C2H01-B, andC2H01-B-GZ simulations (Figures 7-75, 7-76, and7-77, respectively) causes the simulations to changeabout as much as is caused by a change in hydraulicconductivity of half an orderof magnitude (Figures 7­41, 7-42, and 7-43), as expected. The change in theC2H01-A simulation (Figure 7-75) was comparableto that caused by a 0.1-MPa change in formationpore pressure (Figure 7-49), while the changes inthe C2H01-B and C2H01-B-GZ simulations weregreater than those caused by 0.1-MPa pressurechanges (Figures 7-50 and 7-51, respectively). Inthe case of C2H01-C (Figure 7-78), the uncertaintyin test-zone compressibility has little effect on thesimulations (separate simulation lines are not resolvableon the figure) because of the inclusion of arelatively high value of hydraulic conductivity. In thecases of C2H02 and L4P51-A (Figures 7-79 and7-80, respectively), the ranges in calculated testzonecompressibilities are small, and the simulationsemploying the different values differ correspondinglylittle. The uncertainty in test-zone compressibilityfor SOP01 changes the simulation (Figure7-81) about as much as does a unit changewithin the order of magnitude of the best-fit value ofhydraulic conductivity (Figure 7-47), and a little morethan does a 0.1-M Pa change in formation porepressure (Figure 7-55). The uncertainty in test-zonecompressibility for S1P71-A changes the simulation(Figure 7-82) slightly more than do the standardchanges in hydraulic conductivity (Figure 7-48), formationpore pressure (Figure 7-56), and distance tothe zero-flow boundary (Figure 7-58).110


4.53.5ca a..~ 2.5-~::lenen~ 1.5a..0.5ITest C2H01-A, Room C20 Da~ I Test Zone 2.09 - 2.92 m, Vertically Down- SimulationArgillaceous Halite, Map Units 4 and 5-K = 2.0 X 10. 11 rnIs (k = 3 x 10. 18 m 2 )S5 = 9.5 X 10. 8 m· 1r----p' = 0.5 MPaTest-Zone Compressibility:C 1 = 3.82 X 10. 9 Pa- 1C 2 = 1.21 x 10. 9 Pa- 1HistoryC 3= 3.82 x 10. 10 Pa- 1 - >-- - ,.--k C1~rCl'C~~~3 ~""'"History -I Simulation _I I I IHistory-0.5o 5 10 15 20 25 30to - 1988217.5464Time Since Hole Cored (days)TRI-6344·625·0Figure 7-75. Simulation of the Test-Zone Fluid-Pressure Response During C2H01-A TestingShowing the Simulation's Sensitivity to Test-Zone Compressibility.3.5Test C2H01-B, Room C2Test Zone 4.50 - 5.58 m, Vertically DownArgillaceous Halite, Map Unit 0oData- Simulation2.5~::len~ 1.5'-a..0.5Hislory{K = 3.9 X 10- 14 m/s (k = 5 x 10- 21 m 2 )S5 = 9.5 X 10. 8 m·1p' = 3.15 MPaTest-Zone Compressibili~:C 1= 3.82 X10. 1 Pa- 1C 2= 1.21 x 10. 9 Pa·1C 3= 3.82 x 10. 9 Pa·1} History--- History ----"'1---=--------- Simulation--------1....-0.5 L...L..........................L............'--I............L..&..........................L.....L.-..................I....&........................""..........................I....&-.l.......L.-&...l...............--........Joto = 1988 217.5466255075100125Time Since Hole Cored (days)150175200TRI-6344-626·0Figure 7-76. Simulation of the Test-Zone Fluid-Pressure Response During C2H01-B TestingShowing the Simulation's Sensitivity to Test-Zone Compressibility.111


Test C2H01-B GZ, Room C23.5 Guard Zone 2.92 - 4.02 m, Vertically DownArgillaceous Halite. Map Units 0 - 4c;;-~ 2.5oData- Simulation~::::l(/)(/)~ 1.5c..0.5K = 1.4 x 10- 14 mls (k =2 x 10- 21 m 2 )55 = 9.5 x 10- 8 m·1p' = 4.12 MPaGuard -Zone Compressibility:C 1 = 3.82 x 10- 10 Pa- 1C 2 = 1.21 X 10- 9 Pa- 1C 3 = 3.82 x 10. 9 Pa- 11--- History-------i..~I------Simulation --------..,..~-0.5 L--L .-I- J-J'-J. J-J'-J. J-J--I. ......o2550 75 100 125 150 175 200to ~ 1988217.4687 Time Since Hole Cored (days)TRI-6344-627-0Figure 7-77. Simulation of the Guard-Zone Fluid-Pressure Response During C2H01-B TestingShowing the Simulation's Sensitivity to Guard-Zone Compressibility.7.0oData- Simulationc;;-c..5.0Hi,., {} HistoryTest C2H01-C, Room C2Test Zone 6.63 - 8.97 m, Vertically DownSimulation Thickness 0.96 m, Marker Bed 139::2-Q)....::::l(/)(/)Q)....c..3.01.0K = 7.0 X 10- 12 mls (k = 1 x 10- 18 m 2 )S5 = 1.4 x 10- 7 m- 1p' = 8.05 MPaTest-Zone Compressibility:C 1 = 2.50 X 10- 9 Pa- 1C 2= 3.02 x 10- 9 Pa- 1C 3 = 3.64 X 10- 9 Pa- 1---....~+I----------Simulation ---------••-1.0 '--......._ ............_"----1._.......-.1-_........--'-_........--'-_........--1 .......--1_-1-_'--........_ ......-1o2040608010010 - 198944.4479 Time Since Hole Cored (days)TR 1-6344-62&-0Figure 7-78. Simulation of the Test-Zone Fluid-Pressure Response During C2H01-C TestingShowing the Simulation's Sensitivity to Test-Zone Compressibility.112


9.5 1"""'"'............,..,-r-...........,..................,...T'""'T'"..........,..,-r-........T""T"..............,rr-T'""'T'"'"l"""T...,....,-r-r-r.............."'T""...............,7.55.53.51.5K = 5.7 x 10. 13 mls (k = 8 x 10'20 m 2 )Ss = 1.4X10,7 m,'p' = 9.30 MPaTest-Zone Compressibility:C 1= 9.28 X 10,9 Pa,1C 2= 9.87 X 10,9 Pa,1C 3= 1.05x10,8Pa,1}- Histo~o Data- SimulationTest C2H02, Room C2Borehole Oriented 45° Downward from HorizontalTest Zone 9.47 - 10.66 m, Marker Bed 139Simulated Vertical Thickness 0.66 mI-""'psz.=---- Histo~2550---------I~~I-----Simulation------l..~-0.5 ..L..I-L.. '-'- ..L..I-L.. '-'- '-'- ..L..I-L.. '-'- ....oto - 1989 107.390575100125Time Since Hole Cored (days)150 175 200225250TRI,6344,629-0Figure 7-79. Simulation of the Test-Zone Fluid-Pressure Response During C2H02 Testing Showingthe Simulation's Sensitivity to Test-Zone Compressibility.ca 1.5a..~Q)....::J (J)(J)Q)....a.. 0.5~ }Histo~Histo~o Data- SimulationTest L4P51-A, Room L4Test Zone 3.33, 4.75 m, Vertically DownArgillaceous Halite Including Clay DK = 4,5 X to- 14 mls (k =6 x 10'21 m 2 )Ss = 1.3 X to- 7 m,1p' = 2.75 MPaTest-Zone Compressibility:C 1= 7.01 X 10,10 Pa,1C = 7.16 X 10,10 Pa,12C 3= 7.31 X 10,10 Pa- 1Zero,Flow Bounda~ at r = 2.0 mHisto~ ---l..~It------------- Simulation-------------l...~-0.5 L...L...L..I-L...I....L..........-.......L...L......................1.....L................J....a-L...............I....l'-'-........J..l...................L..........L..I..J.....................L-1...................Joto - 1989 291.58592550 75 100125Time Since Hole Cored (days)150 175 200 225 250TRI,6344-630-QFigure 7-80. Simulation of the Test-Zone Fluid-Pressure Response During L4P51-A TestingShowing the Simulation's Sensitivity to Test-Zone Compressibility.113


4.5 ....................,-.......,....,.........,.........,........-r-...........-,.....,........."T"""I-........-r-T..,.........,-....-r-.........,....,.,........-r-r-T""'T""....................,3.5o Data- SimulationTest SOP01South 1300 Drift, East of E140 DriftTest Zone 3.74 - 5.17 m, Vertically DownArgillaceous Halite Including Clay D(? 2.50-~~:::JII)II)Q)....0-1.50.52575100125K = 6.1 X 10- 14 mls (k =8 x 10- 21 m 2 )Ss = 1.1 X 10,7 m- 1p. = 4.45 MPaTest-Zone Compressibility:C 1 = 1.47x10- B pa,1C 2 = 1.70 x lO- B Pa- 1C 3 = 1.96 x 10- B Pa- 11


Test-zone compressibility was among the most uncertainof the specified parameters. As discussed inSection 6.5, the estimationoftest-zone compressibilitydid not take into consideration potential non-linearitiesand time-varying factors such as changes in the brine/gas ratio inthetest zone, nordid it include gas volumesreleased during pulse withdrawals. Accordingly, thesensitivity analyses discussed above may not havefully examined the true ranges of uncertainty in testzonecompressibility for the different tests.7.2.6 TEST-ZONE-VOLUME COMPENSATIONS.The sensitivities of the best-fit simulations to theinclusion or exclusion of time-varying test-zonevolumecompensations are shown in Figures 7-83through 7-90. These figures compare the best-fitsimulations obtained with test-zone-volume compensationswith simulations obtained using exactlythe same values for the specified and fitted parameters,but without test-zone-volume compensations.In general, the presence or absence of test-zonevolumecompensations makes little difference in thesimulations. The one notable exception is L4P51-A(Figure 7-88). The test-zone-volume compensationhad a significant influence on the L4P51-A simulationfor two reasons: 1) the simulation includes azero-flow boundary, so volume changes within theborehole represent a larger fraction of the totalvolume considered in the model than in the simulationswith no boundaries; and 2) the calculated testzonecompressibility was lower during the L4P51-Atests than during any other tests, causing any volumechanges that occurred to have a larger effect onpressure. In contrast, the other simulation thatincluded a zero-flow boundary, that of the S1 P71-Atests (Figure 7-90), used the highest calculatedtest-zone compressibility of any test. This highcompressibility apparently acted to minimize theeffects of volume changes on test-zone pressure.7.2.7 TEMPERATURE COMPENSATIONS. Thelargest test-zone-temperature fluctuations observedto date during the Salado permeability-testing program(about 1'C) occurred during the L4P51-A andSOP01 testing (Saulnier et al., 1991). The sensitivitiesof the best-fit simulations of these two tests to thepresence or absence of temperature compensationsare shown in Figures 7-91 and 7-92. These figurescompare the best-fit simulations obtained with temperaturecompensations with simulations obtainedusing exactly the same values for the fitted and specifiedparameters, but without temperature compensations.In both cases, the effects of temperature compensationsappear to be insignificant, even thoughtest-zone compressibilities in the two cases differ byabout 1.4 orders of magnitude.7.2.8 SUMMARY OF SENSITIVITY ANALYSES.The following conclusions can be drawn from thesensitivity analyses. The fitted parameters (hydraulicconductivity, formation pore pressure, and distance toazero-flow boundarywhere applicable) can bechangedindividually very little without degrading the matchesbetween the simu lations and the observed data. If twoormore parameters are changed simultaneously, however,the ranges of values that produce acceptablesimulations widen. Within the context of the overallmodel conceptualization and subject to the estimationsmade of the possible ranges of values of thespecified parameters, the hydraulic-conductivity valuesprovided by the modeling appear to be reliable towithin about ± one-half order of magnitude, and formationpore pressure estimates appear to be reliablewithin about ± 0.5 MPa. These uncertainties may bequantified more accurately by future analyses. Estimatesof the distance to a zero-flow boundary arehighly sensitive to the assumed value of specific storage.In most cases, test-zone-volume compensationshave negligible effect on the interpreted parameters.115


4.53.5\.""-caa..2.5~-Q)....::JenenQ)....0-1.50.5I· Simulation with Volume Compensation I- Simulation with No Volume CompensationTestC2H01-A. Room C2Test Zone 2.09 - 2.92 m. Vertically DownArgillaceous Halite. Map Units 4 and 5K ;. 2.0 X 10- 11 rnls (k =3 x 10- 18 m 2 ) History History -Ss = 9.5 X 10-8 m- 1p. = 0.5 MPaC tz = 1.21 x 10- 9 Pa- 1 -- - - _.History ~+-- Simulation -I I I I-0.5o 5 10 15 20 25 30to - 1988 217.5464Time Since Hole Cored (days)TR1-6344-633-0Figure 7-83. Simulation of the Test-Zone Fluid-Pressure Response During C2H01-A TestingShowing the Simulation's Sensitivity to Test-Zone-Volume Compensation.3.5ca-~ 2.5-Q)....::Jenen 1.5~a..0.5} History} History• Simulation with Volume Compensation- Simulation with No Volume CompensationTest C2H01-B, Room C2Test Zone 4.50 - 5.58 m. Vertically DownArgillaceous Halite. Map Unit 0K = 3.9 X 10- 14 rnls (k = 5 x 10- 21 m 2 ) } History5 s = 9.5 X 10- 8 m- 1p. = 3.15 MPaC tz = 1.21 x 10. 9 Pa- 1----+-If---------Simulation----------i..~255075100125150175200to - 1988 217.5466Time Since Hole Cored (days)TRI-6344-634-0Figure 7-84. Simulation of the Test-Zone Fluid-Pressure Response During C2H01-B TestingShowing the Simulation's Sensitivity to Test-Zone-Volume Compensation.116


3.5• Simulation with Volume Compensation- Simulation with No Volume CompensationTest C2H01-B GZ. Room C2Test Zone 2.92·4.02 m, Vertically DownArgillaceous Halite, Map Units 0 - 4...::JlJ)lJ)~a.2.51.50.5K = 1.4Xl0·14m!S(k=2xl0-21m2)Ss = 9.5 X 10- 8 m- 1p. = 4.12 MPaC gz = 1.21 x lO- g Pa- 1r------ History----...1-------Simulation-------I....\0 - 1988217.4687 Time Since Hole Cored (days)TR1-6344-635-0Figure 7-85. Simulation of the Guard-Zone Fluid-Pressure Response During C2H01-B TestingShowing the Simulation'S Sensitivity to Guard-Zone-Volume Compensation.7.5- IfI · Simulation with Volume Compensation I- Simulation with No Volume CompensationCii' 5.5a.:2- ...::JlJ)lJ)~a.3.5f-Hi,roO {} HistoryTest C2H01-C. Room C2Test Zone 6.63 - 8.97 m, Vertically DownSimulation Thickness 0.96 m. Marker Bed 139K = 7.0 X 10- 12 mls (k = 1 x 10- 18 m 2 )Ss = 1.4 X 10- 7 m- 1p. = 8.05 MPaCtz = 3.02 x 10-9 Pa- 11.5JIJ History -I Simulation•-0.5o 20 40 60 80 100to - 1989 44.4479Time Since Hole Cored (days)TRI-6344-636-0Figure 7-86. Simulation of the Test-Zone Fluid-Pressure Response During C2H01-C TestingShowing the Simulation's Sensitivity to Test-Zone-Volume Compensation.117


9.5 .................,..,r-T"'.........,..,'""T"",....,........,....,.....,r-T"'.,..,....,.....,'""T""..............,.....,..............,.....,'"T'"T'""'T"...,.....,.,...,....,..........,..,r-T'".......,K = 5.7 X 10- 13 mls (k = 8 x 10- 20 m 2 )Ss = 1.4 x 10- 7 m·1p' = 9.30 MPa7.5 C tz= 9.87 x 10- 9 Pa·1Cila.. 5.5~-Q)...f/)Q)...::Jf/)a..3.51.5J-History• Simulation with Volume Compensation- Simulation with No Volume CompensationTest C2H02. Room C2Borehole Oriented 45° Downward from HorizontalTest Zone 9.47 - 10.86 m. Marker Bed 139Simulated Vertical Thickness 0.86 mI-----:.,r.=----- History --------1..*1-----Simulation-----I...~-0.5 L...l. ..L..L ...L..L-'- ..L..& ~ ~ ......o255075to - 1989 107.3905Time Since Hole Cored (days)100125150175 200 225 250TRI-6344-637-0Figure 7-87. Simulation of the Test-Zone Fluid-Pressure Response During C2H02 Testing Showingthe Simulation's Sensitivity to Test-Zone-Volume Compensation.Test L4P51-A. Room L4Test Zone 3.33 - 4.75 m. Vertically Down2.5 Argillaceous Halite Induding Clay D~------------------••••••••••••••••••••••••••••00oCila..~ 1.5......Q)::Jf/)f/)Q)a..0.5\ } HistoryHistory• Simulation with Volume Compensation- Simulation with No Volume CompensationK = 4.5 x 10- 14 mls (k =6 x 10. 21 m 2 )Ss = 1.3 X 10- 7 m- 1p' = 2.75 MPaC tz= 7.16 X 10- 10 Pa- 1Zero-Flow Boundary at r = 2.0 m~'f------------Simulation---------------i ..~255075100125150175200225250to = 1989 291.5859Time Since Hole Cored (days)TRI-6344-638-QFigure 7-88. Simulation of the Test-Zone Fluid-Pressure Response During L4P51-A TestingShowing the Simulation's Sensitivity to Test-Zone-Volume Compensation.118


3.5• Simulation with Volume Compensation- Simulation with No Volume CompensationC? 2.5a..~-Q)....:::Jen 1.5enQ)0:0.5• •••TestSOP01South 1300 Drift, East of E140 DriftTest Zone 3.74 - 5.17 m, Vertically DownArgillaceous Halite Including Clay DK = 6.1 xlO- 14 m/s(k=8x10- 21 m 2 )Ss = 1.1x10- 7 m- 1p' = 4.45 MPaC ll= 1.7 x 10- 8 Pa- 1'""-r------------Simulation--------------..... --0.5 L....


2.52.0"@' 1.5a-~ ~ } HistoryQ)'- 1.0:J HistoryenlJ)Q)'-a- 0.5• Simulation with Thermal Effects- Simulation with No Thermal EffectsTest L4P51-A, Room L4Test Zone 3.33 - 4.75 m, Vertically DownArgillaceous Halite Including Clay DK = 4.5 X 10- 14 mls (k = 6 X 10- 21 m 2 )S. = 1.3 X 10- 7 m- 1p' = 2.75 MPaC lz = 7.16 X 10- 10 Pa- 10.0Zero-Flow Boundary at r = 2.0 mHistory ----jr------------Simulation ----------l.~-0.5 L..L..................L..I..........L-L.............L-L-L..l....L........L-L....L..I........L..I....L...I........L..I.........L-L.............L-L-I...................L..I..........L-L...................L..Joto - 1989291.5859255075100125150Time Since Hole Cored (days)175200225250TRI-6344-841-0Figure 7-91. Simulation of the Test-Zone Fluid-Pressure Response During L4P51-A TestingShowing the Simulation's Sensitivity to Temperature Compensation.3.5• Simulation with Thermal Effects- Simulation with No Thermal Effects~-"@' 2.5a-~~ 1.5enQ)'-a-0.5TestSOP01South 1300 Drift, East of E140 DriftTest Zone 3.74 - 5.17 m, Vertically DownArgillaceous Halite Including Clay DK = 6.1 X 10- 14 mls (k =8 x 10- 21 m 2 )Ss = 1.1 X 10- 7 m- 1p' = 4.45 MPaC tz= 1.7 x 10- 8 Pa- 1kI.;------------- Simula~on---------------l.~255075100125150175200225to. 1989 11.59357Time Since Hole Cored (days)TRI-6344-842-QFigure 7-92. Simulation of the Test-Zone Fluid-Pressure Response During SOP01 Testing Showingthe Simulation's Sensitivity to Temperature Compensation.120


Temperature fluctuations in the tested zones wereeither of too low magnitude or occurred too slowly toaffect the simulations significantly.7.3 Discussion of ResultsThe numberoftests discussed in this report is too smallto allow firm conclusions to be drawn about the overallhydraulic properties and behavior of the Salado Formationon a repository orregional scale. However, thedata can be examined for apparent relationships betweenvarious factors, with the expectation that futuretesting will either substantiate orinvalidate the hypothesizedrelationships. Possible relationships, and othergeneral summary observations about the testing, arepresented below.7.3.1 EFFECTSOFDISTURBED-ROCKZONE. Creationof an underground opening in rock causes bothimmediate and long-term changes in the mechanicaland hydraulic properties of the surrounding rock. Dilatationof the rock around an opening may occurimmediately after excavation. Dilatation is the result ofgrain-boundary readjustment and intragranularmicrocracking, especially close to the excavation face,which could increase permeability and porosity. Increasesin porosity would increase specific storageand, at least temporarily, decrease the formation porepressure, while increases in permeability would enhancefluid drainage towards the low-pressure excavation,again decreasing the formation pore pressure.A redistribution of stress also occurs around anyunderground opening in rock because the openingcreates a surface of decreased stress. Brady andBrown (1985) state that stress redistribution around acircular opening in linearly elastic rock in an isotropicstress field extends to a distance from the center of theopening of about five times the radius of the opening(using a stress change of ± 5% from the undisturbedvalue as a criterion). Within thisfive-radii region, radialstresses are lower relative to the far-field undisturbedstress, and tangential stresses are higher. The differencebetween the radial stress and the tangentialstress determines the magnitude of what is referred toas the deviatoric stress. The largest amount of stressredistribution, and hence the highest deviatoric stress,occurs within one radius of the opening. If severalopenings lie within each others' radii of influence, or ifthe rock response is inelastic (plastic), stress-fieldperturbations may go beyond the distance of five timesthe radius of an individual opening. Wawersik andStone (1989) reported that an isotropic stress field inrock salt at the WIPP, representative of conditionsunaffected by the presence of an excavation, wasencountered only at distances greater than 50 m fromWIPP Rooms 1 through 4 (Figure 5-1).Deviatoric stress resulting from stress redistributionaround an opening induces shear strain in the rockmass. Because rock salt experiences time-dependentdeformation (creep) under deviatoric stresses, strainingcould theoretically continue for as long as theopening exists. The resulting differential movementwithin the rock mass may lead to fracturing at variousscales. Permeability can be related to the amount ofmacro- and/or micro-fracturing present at any giventime. Inasmuch as strain and microfracturing mightaccumulate forthe lifetime oftheopening, permeabilitymight increase with time.Holcomb (1988), Borns and Stormont (1988), andothers have studied the types and processes ofdeformation occurring around the WIPP excavations.Borns and Stormont (1988) considered thefollowing processes to be of potential importance tothe WIPP: RectangUlar openings in rock are unstable,and arcuate fracture systems, concave towardsthe openings, develop around the openings toconvert the rectangUlar openings to more stablecircular or elliptical forms. The fracture systems121


define the external boundary of what can be consideredto be the "active" opening (Mraz, 1980). Therock between the surface of the active opening andthe actual excavation face can become decoupledfrom the host rock along a shear plane. Rock nearthe excavation face can also experience brittle failurebecause it is unconfined (and therefore fails at alower strain than confined rock) and undergoes highrates of strain. Shear may also occur along planesof weakness close to the excavation, such as alongclay seams oranhydrite interbeds (Brady and Brown,1985). Extension fractures may develop parallel tothe excavation faces.Because of the changes that can occur in the rockaround an excavation, the affected volume of rock issometimes referred to as a disturbed-rock zone (DRZ).Borns and Stormont (1988) and Stormont (1990b)report evidence for measureable changes in mechanicaland hydraulic properties in the rock around theWIPP excavations extending to distances betweenone and five meters from the excavation face. Holcomb(1988) reported changes in compressional-wave attenuation,and to a lesser degree velocity, which heattributed to an increase in fracture porosity, to adistance of at least three meters from the face of anewly excavated room.All ofthe testing discussed in this report was performedin intervals where stress redistribution must haveoccurred as a result of excavation of the WIPP facility.Furthermore, all test intervals except for those ofC2H01-C, C2H02, and C2H03 extended no fartherthan 5.6 m from a room or drift, and were within abouttwo room radii of the openings. Thus, the interpretedhydraulic properties presented in this report may notbe representative of undisturbed rock, but may reflectpermeabil~yand porosity enhancement and depressurizationwithin the DRZ around the WIPP facility.Possible effects of the DRZ on the observed testresponses are discussed below.7.3.1.1 Comparison of Results fromL4P51-A, SOP01, and SlP71-A. The L4P51-A,SOP01, and S1 P71-A tests involved essentially thesame strata within the test and guard zones. Thus,differences in the hydraulic properties interpretedfrom these tests might be related to differences in theDRZ at these locations. According to Borns andStormont (1988) and Stormont (1990a), a widerexcavation tends to have a more developed DRZthan a narrower excavation of the same age, and anolder excavation tends to have a more developedDRZ than a younger excavation of the same size.HydraUlic properties within the DRZ may also varywith position over the width of a single drift or room(Borns and Stormont, 1988; Stormont, 1990a). TheL4P51 and S1P71 boreholes are in rooms 10.1 mwide, while SOPOl is in a drift that is only 6.1 m wide.However, SOP01 is in the S1300 drift, which was4.5 years old when testing began, whereasthe roomscontaining L4P51 and S1 P71 were only about eightmonths old when testing began at those locations.As a result, the three tests do not provide ideal,controlled-experiment conditions in which only onevariable is altered between experiments. We maynot, therefore, be able to separate the effects ofexcavation age and size.Whether or not the hydraulic properties at SOP01 aresignificantly different from those at L4P51 and Sl P71,the hydraulic properties at the latter two locationsmight be expected to be similar because of similarroom ages and sizes. However, the estimated hydraulicconductivities of the test-zone intervals of L4P51-Aand S1 P71-A differ by an order of magnitude (4.5 x10- 14 mls vs. 4.0 x 10- 13 mis, respectively), while that forSOP01 is intermediate (6.1 x 10- 14 mls). The estimated122


formation pore pressures, however, are similar forL4P51-A and S1P71-A (2.75 and 2.95 MPa, respectively),while that at SOP01 is considerably higher(4.45 MPa). L4P51-Aand S1 P71-Aare also similar inthat both sets of tests showed apparent zero-flowboundaries 2 to 3 m from the borehole, while noboundary effects were observed during the testing ofSOP01. Marker Bed 139 was isolated in the guardzones of these holes. The highest guard-zone pressure(0.52 MPa) was observed in SOP01. The guardzonepressure in L4P51-A decreased from 0.3 to0.2 MPa during testing, and no pressure above atmosphericwas observed in the S1 P71-A guard zone.Why the test-zone interval of S1 P71-A should have ahigher formation pore pressure than that of L4P51-A,while the opposite is true of the guard-zone intervals isunknown.In summary, the lowertest- and guard-zone pressuresin L4P51-A and S1 P71-A relative to SOP01 might berelated to increased disturbance resulting from theirbeing in a larger excavation, as might the higherhydraulic conductiv~yof the S1 P71-A test-zone interval.If true, this would indicate that the age of anexcavation is less importantthan its size in determiningthe degree of disturbance in the rock surrounding theexcavation. Stormont (1990a) reached the sameconclusion from examination of extensometer measurements,inclinometer measurements, and gas-flowmeasurements made in boreholes drilled from differentsize rooms. The low hydraulic conductivity of theL4P51-A test-zone interval, however, is not in accordwith this hypothesis. In addition, we have difficultyreconciling the concept of increased disturbance withthe apparent zero-flow boundaries around L4P51 andS1 P71 . If disturbance increases permeability andallows pressure to escape, we would not expect toobserve zero-flow boundaries. Additional testing willbe required before more definitive conclusions can bedrawn about the relationship between an excavation'sage and size and the hydraulic properties within theDRZ.7.3.1.2 Comparison ofResultsfrom C2H01-Cand C2H02. Another location where the DRZ may havehad some influence on the hydraulic properties observedin Marker Bed 139 is in Room C2. Hole C2H01, drilledvertically downward into the floor of the room, is thought tohave encounteredoneormorefractures in MarkerBed139that contributed to the relatively high hydraulic conductiv~(7.0 x 10- 12 mls) observed at that location. The hydraulicconductivity of Marker Bed 139 was lower (5.7 x 10- 13 mls)at hole C2H02, which was drilled underthe rib of the roomat a 4S angle. The pore pressure in Marker Bed 139 washigher at C2H02 (9.30 MPa) than at C2H01 (8.05 MPa).These observations are consistent with disturbance directlyunderthe room creating fractures in Marker Bed 139,orallowing existing fractures to open, causing an increaseinpermeabil~anddecreaseinporepressurecomparedtothe relatively undisturbed cond~ions under the rib of theroom. These observationstherefore suggest thatthe DRZbeneath Room C2 extends at least to a depth of 7 m, thedepth of Marker Bed 139.7.3.1.3 Relationship Between HydraulicConductivity and Distance from an Excavation. Allother things being equal, we would expect to observean inverse relationship between hydraulic conductivityand distance from an excavation because of the relationshipbetweendeviatoric stress andfracturing (Section7.3.1). Figure 7-93 shows a plot of the interpretedhydraulic conductivities of the different test intervalsversus the distances from the centers of those intervalsto the excavations from which they were drilled.With respect to the tests of halite intervals, no consistentcorrelation is observed between hydraUlic conductiv~yand distance from an excavation. The testinterval closest to an excavation, that of C2H01-A, had123


a hydraulic conductivity more than an order of magnitudehigherthan that of any otherhalite interval, but thehydraulic conductivities of the other five intervals liewithin a two-order-of-magnitude range with no apparentrelationship to distance from an excavation.The lack of an observed correlation between halitehydraulic conductivity and distance from an excavationmay be due to natural heterogeneity, a statisticallyinadequate amount of data, and/or other factors suchas excavation size, excavation age, mineralogy, andother sedimentological differences having a largerinfluence on hydraulic conductiVity than distance froman excavation. Alternatively, the absence of a correlationbetween hydraUlic conductivity and distancefrom an excavation may reflect the existence of a timevaryinginelastic deviatoric stress field in rock salt(Wawersik and Stone, 1989). That is, time variation inproperties may mask distance variation in properties.With respect to the tests of Marker Bed 139, hydraulicconductivity does appear to increase with increasingproximity to an excavation (Figure 7-93). This observation,however, is based on only three data points.Additional data will be required to place this conclusionon a firmer basis.The two highest hydraUlic conductivities indicated onFigure 7-93 are from the two shallowest test intervals,the SOP01 guard zone and the C2H01-A test zone.The guard zone for the S1 P71-A testing was evenshallower (1.25 to 2.20 m deep; Figure 7-38), and theapparent hydraulic conductivity of Marker Bed 139 inthat interval was also relatively high (see Section7.1.9.2). The simulations ofthe C2H01-Atests and theSOP01 guard-zone tests produced the worst fits to theobserved data of all the tests (Figures 7-3 and 7-37,respectively). The poor fits may be the result ofdiscrepancies between the model assumption of radialflow in a homogeneous medium and actual flow conditionsin the DRZ close to the excavations. Specifically,flow within portions of the DRZ may be nonradialand dominated by fractures of limited extent. Withintwo or three meters of an excavation, therefore, excavationeffects may have created a DRZ in whichpermeabilities are relatively high and nonradial flowconditions may exist. Beyond three meters,permeabilities are lower and radial-flow models canduplicate the observed test responses.7.3.1.4 Relationship Between FormationPore Pressure and Distance from an Excavation.All other things being equal, we would expect toobserve higher formation pore pressures as distancefrom an excavation increases. Figure 7-94 shows aplot of interpreted formation pore pressures versus thedistances from the centers of the corresponding testintervals to the excavations from which they weredrilled. Considering the data from halite intervals andMarker Bed 139 intervals together, a general trend ofincreasing formation pore pressure with distance froman excavation is evident. However, if only the datafrom the halite intervals are considered (Le., excludeSOP01-GZ, C2H01-C, and C2H02), the trend is lessclear. This is probably due in part to the sparsity ofdata, particularly over a wide range of distances fromthe excavations. Otherfactors, however, such astimevaryinginelastic deviatoric stress fields, must alsohave an influence on the formation pore pressureswithin the halite intervals.The two lowest formation pore pressures shown onFigure 7-94 are from the two shallowest test intervals,the C2H01-A test zone (assuming the contributingzone was 2.09 to 2.92 m deep) and the SOP01 guardzone. Two shallower isolated intervals, the C2H01-Aguard zone (0.50 to 1.64 m deep) and the S1 P71-Aguard zone (1.24 to 2.27 m deep), were apparently atatmospheric pressure only. As discussed in Section7.3.1.3, these intervals may be within disturbed zones124


23EC2H01-B-GZ 0Q) 4C0N 5-0Q)=0"t:l6L4P51-A OO SOP01°C2H01-Bo S1P71-AC2H01-AOEBSOP01-GZ~ 7 -.9 EB C2H01-C.s:::li8-Q)09IEB Marker Bed 139 TestsI10 EB C2H02o -Halite Tests1110- 15 10- 14 10- 13 10- 12 10- 11 10- 10Hydraulic Conductivity (m/s)TRI-6344-643-0Figure 7-93. Interpreted Hydraulic Conductivities Versus Distances From Excavations to theCenters of Tested Intervals.0 I1( ,C2H01-A-GZS1 P71-A-GZ2( ~ffiL4P51-A-GZeSOP01-GZEC2H01-A-Q) 3co C2H01-B-GZ0N 4 L4P51_AdJS1P71-AOSOP01'0Q) 5 OC2H01-B=0"0 6~.87.s:::li 8Q)0 910110 2 3 4 5 6Pore Pressure (MPa)IEB Marker Bed 139 TestsIo Halite TestsC2H01-C EBIC2H02 EB7 8 9 10ITRI-6344-644-QFigure 7-94. Interpreted Formation Pore Pressures Versus Distances From Excavations to theCenters of Tested Intervals.125


around their respective excavations in whichpermeabilities have increased and formation porepressures have decreased. Observations of atmosphericpressure in the guard zones of C2H01-A andS1 P71-A probably reflect the extreme condition ofdirect fracture connection between the isolated intervalsand the overlying excavations. Beyond aboutthree meters' depth, the rock appears to be sufficientlyintact to contain pressures of several MPa.7.3.2 EFFECTS OF MINERALOGY ON HYDRAU·LIC PROPERTIES. Keeping in mind possible influencesof the DRZ, two conclusions can be drawnconcerning mineralogy and hydraulicproperties. First,the anhydrite of Marker Bed 139 (including the underlyingclay E) appears to have an intrinsically higherhydraulic conductivity than halite. The hydraulic conductivityof Marker Bed 139was greater at all locationswhere it was tested than the hydraulic conductivity ofall the halite intervals tested, with the exception of thehalite interval in C2H01-A. This halite interval, however,is believed to be significantly disturbed by itsproximity to the excavation, and not at all representativeof undisturbed halite. In general, Marker Bed 139had a hydraulic conductivity one to two orders ofmagnitude higher than that of halite.Second, impure halite, containing trace amounts ofclay and in some cases polyhalite, appears to be morepermeable than pure halite. This conclusion is lesscertain than the previous conclusion, because testdata from pure halite are available from only one hole,C2H03. Nevertheless, the complete lack of an observablepressure response in C2H03, when contrastedwith the unambiguous responses observed in all impure-halitetest intervals, indicates that the hydraulicconductivity of pure halite must be lower than that ofimpure halite. As the testing program continues,additional data will be collected to support or refute thisconclusion.No conclusions can as yet be drawn concerning theamount of clay that must be present to influencehydraulic conductivity significantly. The test intervalscontaining clay D, an areally persistent clay seam orgroup of clay stringers up to 2 cm thick, had hydraulicconductivities only slightly higher than intervals containingless continuous clay impurities. Additionaltesting combined with quantitative determinations ofclay contents are needed to evaluate the influence ofclay on hydraulic conductivity.7.3.3 RADIUS OF INFLUENCE OF TESTING. Theradius of influence of a hydraulic test depends on thespecific storage of the formation being tested: thelower the specific storage, the greater the radius ofinfluence. Assuming base-case values of specificstorage (Table 6-2), the individual pulse tests discussedin this report had radii of influence ranging fromabout 1to 10m(Table 7-1). The pressure disturbancescaused by hole drilling and entire testing sequencesextended to distances between 4 and 35 m from theboreholes, except in the cases of the L4P51-A andS1 P71-A testing which appeared to encounter zeroflowboundaries 2 to 3 m from the holes. In general, theindividual tests of polyhalitic and argillaceous halitehad radii of influence on the order of 2 m. The tests ofMarker Bed 139 in holes C2H01 and C2H02 hadindividual radii of influence of about 5 m. For both thehalite and Marker Bed 139 intervals, these radii aregreat enoughto provide confidence thatthe test resultsare representative of formation properties beyondpossible damaged zones associated with the boreholes.However, if the maximum specific-storagevalues considered possible, which are thought torepresent extreme conditions within the DRZ, areapplicable, the radii of influence ofthetests could beanthe order of 1 m or less. Attempts will be made in thefuture to measure specific storage directly to resolveuncertainties about the radii of influence of testing.126


As discussed in Section 6.2, the model used for testinterpretation assumes no vertical flow in the formation.Any vertical flow associated with these testswould tend to decrease the horizontal radius of influenceof the tests. Thus, the radii of influence presentedin this report should be considered as maximum values.7.3.4 EVALUATION OF POROUS-MEDIUM AS­SUMPTION. The interpretations presented in thisreport are predicated on an assumption that theSalado Formation is a porous medium. That is, wehave assumed that the Salado contains a continuousnetwork of interconnected pores that providesfor continuous pore-pressure gradients and permeability.Some of the tests we have conducted can beeasily interpreted under this assumption, whereasothers cannot. The responses observed duringtests of Marker Bed 139 where it should be relativelyundisturbed by the excavations (C2H01-C andC2H02) appear to be well represented by a porousmediummodel. The responses to the C2H01-B(both test zone and guard zone) and SOP01 tests ofimpure halite are also well represented by a porousmediummodel. The L4P51-A and S1P71-A tests ofimpure halite, however, provide indications of alimited interconnected pore volume, while the C2H03test of pure halite showed no apparent permeabilityor pore pressure at all. The responses observeddu ring the C2H01-A and SOPO 1-GZtests are thoughtto be heavily influenced by the DRZ and gas generation,respectively, and provide little insight into theadequacy of a porous-medium model.The only location at which the continu~y of the porepressumgradient can be evaluated at more than twopoints is borehole C2H01. The three sets of testsperformed in that hole resulted in six different intervalsbeing isolated. During the C2H01-A tests, the guardzone extended from 0.50 to 1.64 m deep and the testzone extended from 2.09 to 5.58 m deep. As discussedin Section 7.1.1 .1 , the responses observed inthe C2H01-A test zone are thought to represent onlythe interval from 2.09 to (at most) 2.92 m deep; that is,not the portions of the C2H01-A test interval laterincluded in the C2H01-B test and guard zones, whichshowed significantly different responses. During theC2H01-B tests, the guard zone was from 2.92 to 4.02m deep and the test zone was from 4.50 to 5.58 mdeep. During the C2H01-C tests, the guard zoneextended from 4.75 to 5.79 m deep, while the test zoneextended from 6.63 to 8.97 m deep, and includedMarker Bed 139 from 6.80 to 7.76 m deep. Asdiscussed in Section 7.1.3.2, no formation-pore-pressureestimate was obtained from the C2H01-C guardzonedata.Figure 7-95 shows the formation pore pressures interpretedfor each of the five intervals in C2H01 plotted asa function of depth. With the exception of the pressurefrom the C2H01-B test-zone interval, the plot showspressures increasing with depth below the excavation.The pressure from the C2H01-B test-zone interval isanomalous in that it is lower than the pressures bothabove and below. This observation casts doubt on theexistence of a continuous pore-pressure gradient belowRoom C2 and, by extension, on the concept ofcontinuous interconnected porosity. Alternatively, timedependentdeformation processes and vertical heterogeneityin the mechanical properties of the rock mightcombine to produce transient pressure gradients thatappear anomalous. Even if porosity is notcontinuauslyinterconnected across bedding, however, ~ maystill be interconnected within a single bed or map un~.Further investigation into the existence of continuouspore-pressure gradients both within individual bedsand across bedding is being carried out as part of theRoom Q tests at the WIPP (Nowak et aI., 1990).127


O~~-.,.----r--r--.----r--.,.-~--r-__r----r---r-~--r--r----r--"'---,1 } C2H01-A-GZ (0 MPa)23?:"'\. C2H01-A-TZC2H01-B-GZE 4.c; 5 C2H01-B-TZc..Q)Cl 6789100 2 3 4 5 6 7 8 9Pore Pressure (MPa)TRI-6344-645-0Figure 7-95. Interpreted Formation Pore Pressures Versus Depths Below Excavation for the TestedIntervals In Borehole C2H01.Thus, the interpreted results of the Salado permeabilitytests conducted to date are inconclusive with respectto the question of whether or not continuousinterconnected porosity exists within the Salado. Noevidence contradicts the concept of continuous interconnectedporosity within Marker Bed 139. Withinhalite, however, two tests provide indications of porositybeing interconnected only on the scale of about twoto three meters, while others show continuousinterconnected porosity to distances of at least fourmeters from the boreholes. Moreover, while the testsof the C2H01-B test zone and guard zone showed noradial restrictions to porosity (or permeability), theformation pore pressures interpreted for those intervalsindicate that porosity may be limited venically(across bedding) at that location. Additional testing tobe performed over the next several years should helpresolve questions about the porous nature of beddedhalite.128


8. SUMMARY AND CONCLUSIONSThis report presents interpretations of hydraulictests conducted in bedded evaporites of theSalado Formation from 1988 through early 1990.Tests were conducted on ten intervals in sixboreholes drilled from the underground WIPPfacility. A summary of the test-interpretation resultsand conclusions about the hydraulic propertiesand behavior of the Salado Formation arepresented below.8.1 Results of TestingThe first objective of the hydraulic tests was toestimate the permeabilities of different stratigraphicintervals in the Salado Formation aroundthe WIPP facility.Pressure-pulse tests weresuccessfully conducted in five stratigraphicintervals. Interpreted hydraulic conductivitiesrange from 1.4 x 10- 14 to 2.0 x 10- 11 m/s for haliteintervals, and from 5.0 x 10- 13 to < 4 x 10-11mls foranhydrite Marker Bed 139. Testing of an interval ofrelatively pure halite was unsuccessful because nopressure response was observed. Sensitivityanalyses suggest our uncertainty in estimatedhydraulic-conductivity values is about ± one-halforder of magnitude in all cases.The second objective of the testing program wasto estimate formation pore pressures withindifferent stratigraphic intervals around the WIPPfacility.No pressure above atmospheric wasobserved in isolated intervals within two meters ofthe WIPP excavations.Estimated pore pressuresbeyond two meters from the excavations rangedfrom 0.5 to 9.3 MPa. The highest pore pressures,8.05 and 9.30 MPa, were estimated from testsperformed in Marker Bed 139. Sensitivity analysesshow our uncertainty in estimated formation porepressures to be on the order of about ± 0.5 MPa.The third objective of the tests was to determinewhether or not hydraulic boundaries would beencountered in the Salado on the scale of testing.Tests of five of the intervals had interpreted radii ofinfluence ranging from about 4 to 35 m, with noindications of hydraulic boundaries. Tests of twointervals showed apparent zero-flow boundaries atdistances of 2.0 and 2.8 m from the boreholes.Two other tests, conducted in intervals 2 to 3 mfrom the excavations, showed hydraulic behaviornot well represented by a radial-flow model.Thisbehavior may have been related to limitedfracturing within a disturbed-rock zone around theexcavations.The fourth objective was to define the distance(s)to which the presence of the WIPP facility hasaffected hydraulic properties and formation porepressures in the surrounding rock.Hydraulicconductivity and pore pressure appear to be mostaffected within 2 to 3 m of the facility.interpreted hydraulic conductivity ofThea haliteinterval within this zone was two orders ofmagnitude higher than the hydraulic conductivityof any other halite interval. The hydraulicconductivity of Marker Bed 139 also appears to behigher within several meters of an excavation thanit is at greater distances.However, the distancebeyond which the hydraulic conductivity of eitherhalite or Marker Bed 139 is completely unaffectedby the presence of the excavations cannot bedetermined with the data currently available.Formation pore pressures within 3 m of theexcavations are low, ranging from atmospheric to0.5 MPa. Pore pressures beyond 3 m of theexcavations are variable, ranging from about 2.7 to9.3 MPa. The observation that lower porepressures are observed in halite up to 6 m from theexcavation than in Marker Bed 139 6.8 to 10.7 mfrom the excavation suggests that the halite hasbeen depressurized by flow towards theexcavation and/or by creation of new pore spaceby rock deformation. No data are as yet available to129


define formation pore pressures in the totalabsence of excavation effects.The database from permeability tests of the Saladois not currently large enough to allow us to achieveour fifth objective. which was to differentiatebetween different mechanisms/models of brineflow through evaporites. One possibility is thatcontinuous. albeit slow. flow occurs throughevaporites in response to continuous porepressuregradients as it does through otherporous media.A second possibility proposed byMcTigue et al. (1989) is that flow only occurs afterinitially isolated pores are interconnected by sheardeformation around an opening.Once the poresare interconnected. brine in the pores that hadbeen at a pressure approaching lithostatic can flowtowards the pressure sink represented by theopening. with creep then closing the pores andthereby helping to maintain the flow. The hydraulicbehaviors observed during the Salado permeabilitytesting program to date cannot be uniquelyascribed to either mechanism of brine flow. This isdue. in part, to uncertainty as to whether or not anyof the tested intervals discussed in this report weresufficiently far from the excavations to beunaffected by deviatoric stress resulting from theexcavations.The two possible mechanisms ofbrine flow discussed above are also not necessarilymutually exclusive. Deformation and creepcould act simply to enhance already-existing flow.8.2 Future Testing Plans and ConsiderationsWhile this report was being prepared. tests of nineadditional intervals were initiated.These includetests of Marker Bed 139 (L4P51-A guard zone,S1P72, SCP01 [Figure 5-1]). anhydrite "c"(S1P71-B and L4P51-B), map unit 0 and/or thepolyhalitic halite between map unit 0 and MarkerBed 139 (S1 P72 guard zone and SCP01 guardzone), halite between clay D and anhydrite "c"(L4P51-B guard zone), and Marker Bed 138(S1 P73-B). Other tests are planned to examinethe hydraulic properties of anhydrites "a," "b," and"c," Marker Beds 138, 139, and 140. various clayseams/stringers, and other map units near theWIPP disposal horizon.However, efforts will bemade to perform these new tests at greaterdistances from the excavations than were the testsdiscussed in this report. Testing at greaterdistances from the excavations should provideinformation on hydraulic properties and behaviorbeyond the range of potential excavation effects.The new tests will not consist solely of pulsewithdrawaltests, but will also include pulseinjectiontests, constant-pressure flow tests, andcross-hole interference tests. The need for pulseinjectiontests was shown by the tests of C2H03,L4P51-A, and S1 P71-A.When conditions of littleor no pressure buildup are observed, as they wereat C2H03, pulse-injection tests will allow us todifferentiate between simple depressurization andextremely low (zero?) permeability.When apparentzero-flow boundaries are encountered,pulse-injection tests will be performed to attemptto increase the pressure in the test interval andcounteract the apparent depletion effects of thepulse withdrawals. The behavior we observeshould indicate whether or not we are truly dealingwith a small. finite volume of fluid.Where preliminary pulse-test interpretation indicateshydraUlic conductivities on the order of10-13 m/s or higher, constant-pressure flow testswill also be performed.Constant-pressure flowtests are insensitive to test-zone compressibilityand will allow confirmation of pulse-test interpretationsand evaluation of potential errors in the pulsetestanalyses.Flow tests may also provideadditional information on the presence or absenceof free gas at different testing locations.The radii of influence obtained from the interpretationof the tests of Marker Bed 139 in boreholes130


C2H01 and C2H02 indicate that cross-holeinterference testing between holes 5 to 10m apartmay be feasible in Marker Bed 139.Interferencetests allow reliable determination of the value ofspecific storage, whereas single-hole pressurepulsetests, in practice, do not.An interferencetest would probably take the form of a constantpressureflow test at one hole, while monitoringthe pressure response at one or more nearbyholes.Testing in horizontal holes will be avoided in thefuture.The inability to remove all entrapped airfrom test zones in horizontal holes results inunacceptable uncertainty in the test-zone compressibility.Tests of the map units within the wastedisposalhorizon will be performed in holes angledupward or downward enough to allow completefilling of the test zones with brine.Future test-interpretation efforts will include theuse of other types of numerical models to addressfactors not considered in this report, such as partialpenetrationeffects, the nature of the flow fieldaround an inclined borehole, pressure-dependenttest-zone compressibility, two-phase flow, andcreep. Factors potentially affecting specific storagein halite will also be studied in greater depth.Depending upon the results of these efforts,some of the test interpretations presented in thisreport could be modified.8.3 ConclusionsThe tests discussed in this report have demonstratedthat the hydraulic properties of beddedevaporites can be determined from in situhydrogeologic testing.Hydraulic conductivities ofevaporites are low (10- 14 to 10-11 mls) whencompared to those of most other water-bearingrock types, but they can be estimated usingtechniques and equipment specifically designedfor low-permeability media.Questions remain,however, as to the nature and degree of interconnectedporosity and permeability naturallypresent in halite. Hydraulic conductivities werefound to increase, and formation pore pressuresdecrease, with increasing proximity to the undergroundexcavations.Whether or not any of thetests can be considered to be unaffected by rockresponse to the excavations (deviatoric stress) isas yet unknown. This question can probably onlybe resolved by testing at greater distances fromthe excavations to establish the distance beyondwhich hydraulic properties remain relativelyconstant. A comparison of the hydraulic behaviorsobserved within and beyond the region influencedby deviatoric stress should provide insight into themechanisms affecting brine flow throughevaporites.131


9. REFERENCESBechtel National, Inc. 1985. Quarterly Geotechnical Field Data Report, September 1985, DOE-WIPP 218(Carlsbad, NM: US DOE).Bechtel National, Inc. 1986. Interim Geotechnical Field Data Report, Fall 1986, DOE-WI PP 86-012(Carlsbad, NM: US DOE).Black, S.R, Newton, R.S., and Shukla, O.K., editors. 1983. Results of Site Validation Experiments, WasteIsolation Pilot Plant (WIPP) Project, Southeastern New Mexico, Volume II, TME 3177 (Albuquerque, NM:US DOE).Borns, D.J. 1985. Marker Bed 139: A StUdy of Drillcore From a Systematic Array, SAN085-0023(Albuquerque, NM: Sandia National Laboratories).Borns, D.J., and Stormont, J.C. 1988. An Interim Report on Excavation Effect Studies at the WasteIsolation Pilot Plant: The Delineation of the Disturbed Rock Zone, SAND87-1375 (Albuquerque, NM:Sandia National Laboratories).Brady, B.H.G., and Brown, E.T. 1985. Rock Mechanics for Underground Mining (London: George Allen &Unwin), 527 p.Bredehoeft, J.D., and Papadopulos, S.S. 1980. "A Method for Determining the Hydraulic Properties ofTight Formations," Water Resources Research 16(1) :233-238.Brodsky, N.S. 1990. Crack Closure and Healing Studies in WIPP Salt Using Compressional Wave Velocityand Attenuation Measurements: Test Methods and Results, SAND90-7076 (Albuquerque, NM: SandiaNational Laboratories).Carmichael, R.S., editor. 1984. CRC Handbook of Physical Properties of Rocks, Volume 11/ (Boca Raton,FL: CRC Press), 340 p.Ciinco, H., Miller, F.G., and Ramey, H.J., Jr. 1975. "Unsteady-State Pressure Distribution Created ByaOlirectionally Drilled Well," J. Pet. Tech. 27:1392-1400.Craft, B.C., and Hawkins, M.F. 1959. Applied Petroleum Reservoir Engineering (Englewood Cliffs, NJ:Prentice-Hall, Inc.), 437 p.Cygan, R.T. 1991. The Solubility of Gases in NaCI Brine and a Critical Evaluation of Available Data,SAND90-2848 (Albuquerque, NM: Sandia National Laboratories).O,eal, D.E., Abitz, RJ., Belski, D.S., Case, J.B., Crawley, ME, Deshler, R.M., Orez, P.E., Givens, C.A.,King, RB., Lauctes, BA, Myers, J., Niou, S., Pietz, J.M., Roggenthen, W.M., Tyburski, J.R., and Wallace,132


M.G. 1989. Brine Sampling and Evaluation Program 1988 Report, DOElWIPP 89-015 (Carlsbad, NM: USDOE).Deal, D.E., Case, J.B., Deshler, A.M., Drez, P.E., Myers, J., and Tyburski, J.A. 1987. Brine Sampling andEvaluation Program Phase /I Report, DOEIWIPP 87-010 (Carlsbad, NM: US DOE).Desai, C.S., and Varadarajan, A. 1987. "A Constitutive Model for Quasi-Static Behavior of Rock Salt," J.Geophys. Res. 92(B11 ):11,445-11,456.Domenico, P.A. 1972. Concepts and Models in Groundwater Hydrology (New York: McGraw-Hili), 405 p.Earlougher, A.C., Jr. 1977. Advances in Well Test Analysis. Monograph Volume 5 (Dallas, TX: Soc PetEng of AIME), 264 p.Freeze, A.A., and Cherry, J.A. 1979. Groundwater (Englewood Cliffs, NJ: Prentice-Hall Inc.), 604 p.Gevantman, L.H., editor. 1981. Physical Properties Data for Rock Salt. NBS Monograph 167 (Washington,DC: National Bureau of Standards), 288 p.Green, D.H., and Wang, H.F. 1990. "Specific Storage as a Poroelastic Coefficient," Water ResourcesResearch 26(7):1631-1637.Hantush, M.S. 1964. "Hydraulics of Wells," in Chow, V.T., editor, Advances in Hydroscience (New York:Academic Press) 1:281-432.Hantush, M.S. 1966. "Analysis of Data from Pumping Tests in Anisotropic Aquifers," J. Geophys. Res.71 (2) :421-426.Holcomb, D.J. 1988. "Cross-Hole Measurements of Velocity and Attenuation to Detect a Disturbed Zonein Salt at the Waste Isolation Pilot Plant," in Cundall, P.A., Sterling, A.L., and Starfield, A.M., editors, KeyQuestions in Rock Mechanics: Proceedings of the 29th U.S. Symposium, University of Minnesota,Minneapolis, 13-15 June 1988 (Rotterdam: A.A. Balkema), pp. 633-640.Holt, A.M., and Powers, D.W. 1990. Geologic Mapping of the Air Intake Shaft at the Waste Isolation PilotPlant, DOE/WIPP 90-051 (Carlsbad, NM: US DOE).Hsieh, P.A., Neuman, S.P., and Simpson, E.S. 1983. Pressure Testing of Fractured Rocks--A MethodologyEmploying Three-Dimensional Cross-Hole Tests, NUREG/CR-3213 (Washington, DC: US NRC).Ibrahim, A.W., Borns, D.J., and Jung, Y. 1989. "Mapping Fractures in Salt with the Seismic Method," SEGAbstracts 59(1) :252-254.133


Jensen, A.L. 1990. Borehole Closure and Test Zone Volume Determination Program for Brine­Permeability Test Results Within the Waste Isolation Pilot Plant Underground Facility, SAND90-0228(Albuquerque, NM: Sandia National Laboratories).Jones, C.L., Bowles, C.G., and Bell, K.G. 1960. Experimental Drill Hole Logging in Potash Deposits of theCarlsbad District, New Mexico. USGS Open-File Rpt 60-84 (Washington, DC: US GPO), 25 p.Krieg, R.D. 1984. Reference Stratigraphy and Rock Properties for the Waste Isolation Pilot Plant (WIPP)Project, SAND83-1908 (Albuquerque, NM: Sandia National Laboratories).McTigue, D.F. 1989. "Observations on Brine Flow Mechanisms in WIPP Repository Salt Based on Datafrom a Room D Borehole." Memorandum to Distribution, March 15, 1989, Division 1511, Sandia NationalLaboratories, Albuquerque, NM.McTigue, D.F., Finley, S.J., and Nowak, E.J. 1989. "Brine Transport in Polycrystalline Salt: FieldMeasurements and Model Considerations," Eos Transactions 70(43):1111.Mraz, D. 1980. "Plastic Behavior of Salt Rock Utilized in Designing a Mining Method," CIM Buffetin 73:11­123.Neuzil, C.E. 1982. "On Conducting the Modified 'Slug' Test in Tight Formations," Water ResourcesResearch 18(2):439-441.Nowak, E.J., McTigue, D.F., and Beraun, R. 1988. Brine Inflow to WIPP Disposal Rooms: Data, Modeling,and Assessment, SAND88-0112 (Albuquerque, NM: Sandia National Laboratories).Nowak, E.J., Finley, S.J., and Howard, C.L. 1990. Implementation of Initial Tests in the Brine Inflow Room(Room 0) of the Waste Isolation Pilot Plant, SAND90-0611 (Albuquerque, NM: Sandia NationalLaboratories).Palciauskas, V.V., and Domenico, P.A. 1989. "Fluid Pressures in Deforming Porous Rocks," WaterResources Research 25(2) :203-213.Perry, R.H., and Chilton, C.H., editors. 1973. Chemical Engineers' Handbook, Fifth Edition (New York:McGraw-Hili).Peterson, E.W., Lagus, P.L., and Lie, K. 1987. WIPP Horizon Free Field Fluid Transport Characteristics,SAND87-7164 (Albuquerque, NM: Sandia National Laboratories).Pfeifle, T.W., Mellegard, K.D., and Senseny, P.E. 1983. Preliminary Constitutive Properties for Salt andNonsaft Rocks From Four Potential Repository Sites, ONWI-450 (Columbus, OH: Battelle MemorialInstitute).134


Pfeifle, T.W., and Senseny, P.E. 1981. Elastic-Plastic Deformation of Anhydrite and Polyhalite asDetermined From Quasi-Static Triaxial Compression Tests, SAND81-7063 (Albuquerque, NM: SandiaNational Laboratories).Pickens, J.F., Grisak, G.E., Avis, J.D., Belanger, D.W., and Thury, M. 1987. "Analysis and Interpretation ofBorehole Hydraulic Tests in Deep Boreholes: Principles, Model Development, and Applications," WaterResources Research 23(7) :1341-1375.Powers, D.W., and Hassinger, B.W. 1985. "Synsedimentary Dissolution Pits in Halite of the PermianSalado Formation, Southeastern New Mexico," J. Sed. Pet. 55(5):769-773.Powers, D.W., Lambert, S.J., Shaffer, S.-E., Hill, L.R., and Weart, W.D., editors. 1978. GeologicalCharacterization Report, Waste Isolation Pilot Plant (WIPP) Site, Southeastern New Mexico, 2 volumes,SAND78-1596 (Albuquerque, NM: Sandia Laboratories).Saulnier, G.J., Jr., and Avis, J.D. 1988. Interpretation of Hydraulic Tests Conducted in the Waste-HandlingShaft at the Waste Isolation Pilot Plant (WIPP) Site, SAND88-7001 (Albuquerque, NM: Sandia NationalLaboratories) .Saulnier, G.J., Jr., Domski, P.S., Palmer, J.B., Roberts, R.M., Stensrud, W.A., and Jensen, A.L. 1991.WIPP Salado Hydrology Program Data Report #1, SAND90-7000 (Albuquerque, NM: Sandia NationalLaboratories) .Skokan, C.K., Pfeifer, M.C., Keller, G.V., and Andersen, H.T. 1989. Studies of Electrical and ElectromagneticMethods for Characterizing Salt Properties at the WIPP Site, New Mexico, SAND87-7174 (Albuquerque,NM: Sandia National Laboratories).Stensrud, WA: Bame, MA, Lantz, K.D., Cauffman, T.L., Palmer, J.B., and Saulnier, G.J., Jr. 1988. WIPPHydrology Program, Waste Isolation Pilot Plant, Southeastern New Mexico, Hydrologic Data Report #6,SAND87-7166 (Albuquerque, NM: Sandia National Laboratories).Stormont, J.e. 1990a. "Discontinuous Behaviour Near Excavations in a Bedded Salt Formation," Int. J.Mining and Geological Engineering 8:35-56.Stormont, J.C. 1990b. Summary of 1988 WIPP Facility Horizon Gas Flow Measurements, SAND89-2497(Albuquerque, NM: Sandia National Laboratories).Teufel, L.W. 1981. Mechanical Properties of Anhydrite and Polyhalite in Quasi-Static Triaxial Compression,SAND81-0858 (Albuquerque, NM: Sandia National Laboratories).Touloukian, Y.S., Judd, W.R., and Roy, R.F. 1981. Physical Properties of Rocks and Minerals. McGraw­Hill/Cindas Data Series of Material Properties, Y.S. Touloukian and C.Y. Ho, editors, Volume 11-2, 548 p.135


U.S. Department of Energy. 1983.177 (Albuquerque, NM: US DOE).Quarterly Geotechnical Field Data Report, October 1983, WIPP-DOE­Van Sambeek, L.L. 1987. Thermal and Thermomechanical Analyses of WIPP Shaft Seals, SAND87-7039(Albuquerque, NM: Sandia National Laboratories).Walsh, J.B. 1965. "The Effect of Cracks on the Compressibility of Rock," J. Geophys. Res. 70(2):381­389.Wawersik, W.R, and Hannum, D.W. 1980. "Mechanical Behavior of New Mexico Rock Salt in TriaxialCompression Up to 200oC," J. Geophys. Res. 85:891-900.Wawersik, W.R, and Stone, C.M. 1989. "A Characterization of Pressure Records in Inelastic RockDemonstrated by Hydraulic Fracturing Measurements in Salt," Int. J. Rock Mech. Min. Sci. & Geomech.Abstr. 26(6):613-627.Weast, RC., editor. 1983. CRC Handbook of Chemistry and Physics, 64th Edition (Boca Raton, FL: CRCPress).Westinghouse Electric Corporation. 1989. Geotechnical Field Data and Analysis Report, July 1987-June1988, Volume II, DOEIWIPP 89-009 (Carlsbad, NM: US DOE).Westinghouse Electric Corporation. 1990. Geotechnical Field Data and Analysis Report, July 1988-June1989, Volume II, DOE/WIPP 90-006 (Carlsbad, NM: US DOE).136


APPENDIX ASUMMARY OF SURFACE-BASED HYDRAULIC TESTINGOF THE SALADO FORMATIONFrom 1976 to 1985, a number of hydraulic tests of the Salado Formation were performed in boreholesdrilled from the surface. Most of these tests were intended as reconnaissance tests to try to find evidenceof high permeabilities and pressures, rather than as tests to measure the expected low permeability ofhalite. As a result, little effort was expended trying to establish optimal conditions for testing of lowpermeabilitymedia. Drillstem tests (DSTs), air-injection tests, and/or pressure-pulse tests were performedin boreholes ERDA-9, ERDA-10, AEC-7, AEC-8, Cabin Baby-1, DOE-2, and WIPP-12, but none provideddata that could be reliably interpreted to yield formation permeability and/or pressure values.In 1976, ten DSTs were attempted in borehole ERDA-9 of Salado intervals ranging in thickness from 11.6to 76.5 m (Griswold, 1977). The purpose of the tests was to look for evidence in the Salado Formation ofgeopressured brine flow such as had been observed in the Castile Formation at the ERDA-6 borehole(Griswold, 1977). Accordingly, no effort was made to optimize conditions for testing of very lowpermeability « 10-15 m2; 1 milliDarcy [mOl) media. Three of the DSTs were unsuccessful, as one or bothpackers failed to establish a pressure-tight seat in the borehole. Halliburton Services, the company thatperformed the DSTs, reported permeability values from five of the tests (Sigmon, 1976). One of thesefive tests, and a sixth test, were also interpreted by Sipes, Williams, and Aycock, Inc., the contractor hiredto oversee the DSTs. The seventh test was considered uninterpretable because the buildup dataprovided evidence only of afterflow (wellbore storage) (Sigmon, 1976; Griswold, 1977).The permeabilities interpreted from the six DSTs in ERDA-9 have since appeared in Griswold (1977),Lambert and Mercer (1978), and Mercer (1987) without critical evaluation. Examination of the interpretationspresented by Sigmon (1976) reveals that no flows into the well occurred during the DST flowperiods. Nevertheless, the buildup data were fitted to type curves, and the time matches between thedata and the type curves were used incorrectly to estimate permeabilities. Standard DST buildup analysis(Earlougher, 1977) requires that a flow rate be measured during a flow period. This flow rate is used alongwith the pressure match between the data and a type curve to calculate permeability. The time match isonly used with the permeability obtained from the pressure match to calculate the wellbore-storagecoefficient of the well. The time match alone provides no information on permeability. Thus, thepermeability values presented by Sigmon (1976) from the ERDA-9 DSTs are invalid. The DST interpretationsof Sipes, Williams, and Aycock, Inc., also relied on invalid type-curve-matching procedures and oninvalid Horner analyses because no flows were observed during those tests. Without flow data, the ERDA­9 DSTs simply cannot be interpreted to provide estimates of permeability.Even though invalid interpretations of the ERDA-9 DSTs were reported, the deficiencies of the tests wererecognized by the parties involved. Quoting Griswold (1977), ..... we must conclude that the drill-stem testdid not adequately test the formation. This is not an operational fault of the technique we used, but ratheran indication that extremely long shut-in times (perhaps a month or more) will be required. Such times arenot realistic for conducting active drilling operations. Therefore, the only conclusion that can be drawn137


from the 10 drill-stern tests is that no significant amount of fluid is present in the Salado. Definitive tests asto what trace amounts are present and under what pressures must be determined by other means ..."DSTs were attempted over two intervals of the Salado in borehole AEC-7 in 1979 (Sandia andO'Appolonia, 1983a), over one interval of the Salado in borehole AEC-8 in 1976 (Sandia and O'Appolonia,1983b), and over two Salado intervals in borehole EROA-10 in 1977 (Sandia and D'Appolonia, 1983c),but no interpretable results were obtained from any of these tests. Although pressure buildups wereusually observed when the intervals were shut in, no flows into the wells were observed during the OSTflow periods, which typically lasted one hour or less.Air-injection tests of two 30.5-m intervals of the Salado were attempted in June 1979 in borehole AEC-7(Peterson et aI., 1981). Peterson et al. (1981) interpreted these tests by assuming that the pores in theSalado were dry, containing only gas at atmospheric pressure. This assumption has since been found tobe invalid, as the Salado pores appear, from testing performed in the WIPP underground, to be saturatedwith brine at pressures of up to 11 MPa. The fluid that had been in the AEC-7 borehole since it was drilledwas evacuated 28 days before the air-injection testing began, which may have resulted in partialdesaturation of the rock around the hole. The true saturation state and pressure distribution around theAEC-7 borehole at the time of the air-injection tests cannot now be determined, however, and hence thetests cannot be reinterpreted to provide reliable permeability values.In 1983, OSTs and a slug test were attempted on a 597.5-m interval of the Salado in borehole Cabin Baby­1 (Beauheim et aI., 1983). From a Horner analysis of the second OST bUildup period, Beauheim et al.(1983) reported a maximum average permeability of the interval of 9 x 10- 21 m2 (9 nD). This value wasreported as a maximum because it was derived from the final slope of a Horner buildup curve that wascontinuing to steepen at the end of the OST, and permeability is inversely proportional to the slope ofsuch a curve.Later observations of shut-in pressures at the Cabin Baby-1 wellhead revealed thatpressures had indeed risen higher than the value predicted from extrapolation of the final slope observedduring the OST, confirming that the permeability value reported was an overestimate.Beauheim et al.(1983) also reported a Salado permeability value of 8 x 10-20 m2 (80 nO) based on a poor fit between theslug-test data from Cabin Baby-1 and a type curve. This permeability value is also likely an overestimate,because the type-curve interpretation failed to take into account the transient pressure conditionsexisting before the slug test began. The recovery response observed during the slug test actuallyrepresented a superposition of recovery responses from the earlier DSTs and other wellbore conditions inaddition to the slug test itself, and therefore was more rapid, leading to a higher interpreted permeability,than it would have been had the slug test been the only stress on the system. Thus, the testing at CabinBaby-1 provided only poorly defendable upper bounds on the permeability of the Salado.In 1985, a OST and pressure-pulse tests were attempted over two Salado intervals in borehole OOE-2(Beauheim, 1986). The OST was performed over a 34.7-m interval of the Salado that included MarkerBeds 138 and 139. The test-interval pressure was given nearly 21 hr to stabilize before testing began,but this proved to be an inadequate period. The OST consisted of a 21-minute flow period followed by a23.3-hr buildup period. From a Horner analysis of the buildup data, Beauheim (1986) estimated amaximum average permeability of the interval of 3 x 10- 19 m 2 (300 nO). This value was reported as a138


maximum because the Horner bUildup curve was continuing to steepen at the end of the monitoringperiod. Two pressure-pulse tests were attempted over a 626.4-m interval of the Salado in DOE-2. Thetests were preceded by a 15-hr pressure-stabilization period.Attempted type-curve interpretation ofthese tests failed because the two data sets provided inconsistent estimates of the static formationpressure and fit the type curves poorly.obtained from the pulse tests.Therefore, no defendable estimates of permeability wereIn summary, the testing at DOE-2 resulted only in an overestimate of thepermeability of one interval. Both the DST and pulse tests at DOE-2 provided qualitative indications thatcarefully controlled permeability tests of the Salado would require testing durations on the order of weeksto months.DSTs were also performed over four Salado intervals in borehole WIPP-12 in 1985 (Beauheim, 1987).The primary purpose of the tests was to identify the source(s) of high pressures observed at the WIPP-12wellhead, not to provide data for quantitative permeability analysis. Thus, no attempt was made to allowtest-interval pressures to stabilize before beginning the DSTs, and all tests were terminated while thebuildup curves (on a Horner plot) were continuing to steepen. No attempt has been made to derivepermeability values from these tests because the test data are unsuitable for that purpose. However, theresponses observed during the WIPP-12 testing provided additional qualitative indications that apermeability test of the Salado would require a testing duration on the order of weeks to months.Following the DOE-2 and WIPP-12 testing, we concluded that the time periods required for successfulpermeability testing of the Salado rendered surface-based testing in deep boreholes unfeasible.Economic considerations involving the costs of deep drilling and maintaining necessary equipment atremote surface sites for long periods of time, and technical difficulties that had been encountered, suchas a lack of good packer seats and numerous equipment failures, contributed to this conclusion. Thus, allfuture hydraulic testing of the Salado was planned to be conducted in the underground WIPP facility,where access to the formation at the facility horizon could be easily obtained, and where tests could bestarted and conducted more economically with more control over the mechanics of testing and equipment.139


REFERENCESBeauheim, R.L. 1986. Hydraulic-Test Interpretations for Well DOE-2 at the Waste Isolation Pilot Plant(WIPP) Site, SAND86-1364 (Albuquerque, NM: Sandia National Laboratories).Beauheim, R.L. 1987. Interpretations of Single-Well Hydraulic Tests Conducted At and Near the WasteIsolation Pilot Plant (WIPP) Site, 1983-1987, SAND87-0039 (Albuquerque, NM: Sandia NationalLaboratories).Beauheim, R.L., Hassinger, B.W., and Klaiber, J.A. 1983. Basic Data Report for Borehole Cabin Baby-1Deepening and Hydrologic Testing. WTSD-TME-020 (Albuquerque, NM: US DOE).Earlougher, R.C., Jr. 1977. Advances in Well Test Analysis. Monograph Volume 5 (Dallas, TX: Soc PetEng of AIME), 264 p.Griswold, G.B. 1977. Site Selection and Evaluation Studies of the Waste Isolation Pilot Plant (WIPP), LosMedanos, Eddy County, NM, SAND77-0946 (Albuquerque, NM: Sandia Laboratories).Lambert, S.J., and Mercer, J.W. 1978. Hydrologic Investigations of the Los Medanos Area, SoutheasternNew Mexico, 1977, SAND77-1401 (Albuquerque, NM: Sandia Laboratories).Mercer, J.W. 1987. Compilation of Hydrologic Data From Drilling the Salado and Castile Formations Nearthe Waste Isolation Pilot Plant (WIPP) Site in Southeastern New Mexico, SAND86-0954 (Albuquerque,NM: Sandia National Laboratories).Peterson, E.W., Lagus, P.L., Broce, R.D., and Lie, K. 1981. In Situ Permeability Testing of Rock Salt,SAND81-7073 (Albuquerque, NM: Sandia National Laboratories).Sandia National Laboratories and D'Appolonia Consulting Engineers, 1983a. Basic Data Report forDrillhole AEC 7 (Waste Isolation Pilot Plant - WIPP), SAND79-0268 (Albuquerque, NM: Sandia NationalLaboratories) .Sandia National Laboratories and D'Appolonia Consulting Engineers, 1983b. Basic Data Report forDrillhole AEC 8 (Waste Isolation Pilot Plant - WIPP), SAND79-0269 (Albuquerque, NM: Sandia NationalLaboratories).Sandia National Laboratories and D'Appolonia Consulting Engineers, 1983c. Basic Data Report forDrillhole ERDA 10 (Waste Isolation Pilot Plant - WIPP) , SAND79-0271 (Albuquerque, NM: Sandia NationalLaboratories) .Sigmon, J.E. 1976. Letter on ERDA-9 Drillstem Testing Analysis to John Keesey, Sipes, Williams, andAycock, Inc., Midland, Texas, dated August 9, 1976.140


APPENDIX 8STRATIGRAPHIC UNITS (MAP UNITS) NEAR THE WIPPFACILITY HORIZON141


15--oUlQIllAC£OUS HAUTE11.83x NAUlt)( -x _15.55 CLAY "-21•.17 C~Y W-113.0511.5810---..,.a.l&7.'2POlnw..mc HAUTECLAY LAROIUAC(OU$ HAUTEx _HAUTE-x- :::X,"-x,-)("";,\\;- X - HALITEANHYllltITE (WI-1M)CUY I(- - - - - AIlOIUACEOUS HAUTE'.11x(.:)>-jU:::2:o0::u...WUZ


Table B·1Description of Generalized Stratigraphy·ApproximateDistance FromClay G (Meters)Stratigraphic UnitDescription16.8 to 17.514.2 to 16.813.0 to 14.211.6 to 13.010.4 to 11.69.2 to 10.49.0 to 9.27.6 to 9.0Argillaceous haliteHalitePolyhalitic haliteArgillaceous haliteHaliteHaliteAnhydrite (MB-138)Argillaceous haliteClear to moderate brown, medium to coarsely crystalline.


Table B-1Description of Generalized Stratigraphy (Continued)ApproximateDistance FromClay G (Meters)Stratigraphic UnitDescription7.0 to 7.66.4 to 7.05.1 to 6.44.8 to 5.13.5 to 4.82.3 to 3.52.1 to 2.31.7to 2.10.1 to 1.7HaliteArgillaceous halite(clay J)Halite (map unit 15)Halite (map unit 14)Halite (map unit 13)Polyhalitic halite(map unit 12)Anhydrite("a" - map unit 11)Halite (map unit 10)Halite (map unit 9)Clear, some light moderate brown, coarsely crystalline.


Table B-1Description of Generalized Stratigraphy (Continued)ApproximateDistance FromClay G (Meters)Stratigraphic UnitDescription0.0 to 0.10.0 to -0.7-0.7 to -2.1-2.1 to -2.7-2.7 to -3.5-3.5 to -4.2-4.2 to -4.3-4.3 to -4.4-4.4 to -6.7Anhydrite("b" - map unit 8)Halite (map unit 7)Halite (map unit 6)Halite (map unit 5)Argillaceous halite(map unit 4)Halite (map unit 3)Argillaceous halite(map unit 2)Halite (map unit 1)Halite (map unit 0)Light to medium gray, microcrystalline anhydrite. SCatteredhalite growths. Thin gray clay seam G at base of unit.Clean to light/medium gray, some moderate reddish orange/brown. Coarsely crystalline, some fine and medium. :::;1%brown and gray clay. Locally up to 2% clay.


Table B-1Description of Generalized Stratigraphy (Continued)ApproximateDistance FromClay G (Meters)Stratigraphic UnitDescription-6.7 to -7.7-7.7to-B.6-B.6to -9.5-9.5 to -11.0-11.0to-11.5-11.5to 13.0-13.0 to 14.4-14.4tO-16.2-16.2 to -16.3Polyhalitic haliteAnhydrite (MB-139)HalitePolyhalitic haliteHalitePolyhalitic haliteHalitePolyhalitic haliteAndydrite ("c")Clear to moderate reddish orange. Coarsely crystalline, somemedium locally.


Table B-1Description of Generalized Stratigraphy (Concluded)ApproximateDistance FromClay G (Meters)Stratigraphic UnitDescription-16.3 to -20.0-11.5 to 13.0-13.0 to -14.4HalitePolyhalitic haliteHaliteClear to medium gray and moderate brown. Medium to coarselycrystalline, some fine locally. :S;1% polyhalite, locally polyhalitic.


148


APPENDIX CCORE LOGSC2H01C2H02C2H03N4P50L4P51-ASOP01S1 P71-A149


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Pa~e-i Of.iCORE-LOG INVEN10RYI t-.TUl...'\ 1.c~~ole;; ••fOF;~~I cooPROJECT: \.JJ\-?? BOREHOLE: ~\ - A CORE LOGGED B~LOCATION: l'"\ ELEVATION: \'2..'1"t,z.-:o.,odt ~.~ ,",~c\cmN \\\ CD~. "\S'\'OCOORDlNAlES: ~ CD2..~'"'z.. .liUZiP DIAMETER: "'\ " DATE:i0.6 r If'iROOM: \....~ COClAfl: DR1LlIN3 TIME: \,6-'3 \.. CI.IINE: \A\~ c.e.SING DRILLE~~DRILlIN3 METHOOISl; A',f (2 o\o.~1 DRIlUN3 COMPANY:ORIlllN3 APPARATUS: lCNjyeuc DbS ~ C?'esI.JJ0 -':2 LU i:i: (J)::>E c: 0 UJUJ Q;- LUE: c:~~> ::>IJJ0 0 l-I- e:::: I:Lu B00 llJ W0 '1 ~;~1):50 t--DESCRIPTIONREt-',A.RKS~:~-'"\..s-S-'. ~""I


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PAGE_~_OF__? __ CORE-LOG INVENTORYFORM 1400 =PROJECT:_~~f'f'__ BOREHOLE:~~\ LOGG..E.Q 8Y~_1__----::;2..~LOCATION:_~B..QQ..::1~; HN '8:'''I\.~~1.ELEVATION:~b?~-,-~l.&"'ft DATE: 'iL~Q_COORDINATES:.52'1~·!S",e, DIAMETER:__L{~__ DRILLING DATE:_~iK..1_ROOM:...?.J~QS>_d...:; H COLLAR:_____ DRILLING TIME:_~.:...~~MINE:_~1.P£ CASING:_____ R k' )t-----------I.----------t DRILLER:__~~__~~_DRILLING METHOD(S):__hiC-_£Q:1:9--""-t _DRILLING..--.. 0z ::E w=:> .......... Ct::W Ct:: w:r:::E >w I- 0I- Ct:: 0- U0 w wUAPPARATUS:_1~~t--e~~_!)~..?__0 Ct::~$:0·Ẉ..J(/)L-.0 We::: Ct::0..:Ju I-~ U0 DESCRIPTIONDRILLINGCO.:_~LE-~_fJ-i2--~~_----REMARKS~ ..i- •174


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APPENDIX DFACTORS AFFECTING TEST-ZONE COMPRESSIBILITYSection 6.5 briefly describes a number of factors which potentially affect test-zone compressibility (C tz)'1) non-packertest-tool-component compressibility - The volumes of various metal components of the test toolvary in response to changes in test-zone pressure.2) bQrehQle cQmpressibility - The radius Qf the borehQle varies in response tQ applied test-ZQne pressure.3) axial test-tQQI movement - The test tool has a tendency to move intQ and Qut Qf the borehole in responseto applied test-zone pressure.4) test-zQne-packerdefQrmation - The packer-inflation-pressure data indicate that the packer vQlume changesduring testing. These changes can be assumed to affect the test-zone volume also.5) entrappedlcreated gas in the test ZQne - Gas was observed during the venting Qf SQme test ZQnes duringpulse withdrawals. A separate gas phase in the test ZQne WQuid affect C tz'6) creep closure of the borehole - Halite and argillaceous halije are considered tQ undergo inelastic steadystatecreep in underground openings (Krieg, 1984; Van Sambeek, 1987). Therefore, creep closure maypotentially cause borehole-vQlume changes.Factors 1, 2, and 3 above can be quantified in terms of changes in the test-zone volume and therefore can becompensated for in the test analysis. Sections 0.1, 0.2, and 0.3 discuss the mechanisms associated withfactors 1,2, and 3, and presentthe equations used to calculate the volume changes associated with each factor.Sections 0.4 through b.6 discuss possible causes of factors 4,5, and 6. Section 0.6 shows that the impact ofcreep closure is most likely insignificant.0.1 Non-Packer-Related Tool Compressibility.All parts of the multipacker test tool in contact with the test-zone fluid can undergQ pressure-related expansionand contraction. Figures 3-1 and 3-2 show typical test-tool configurations, with Figure 3-2 showing themultipackertesttoQI equipped with radial and axial LVOTs. The compQnentsof interest are: thetest-zone-packerfixed-end sub, spacers, swivel mechanism, radial-LVOT carrier, transducerlvent-line feed-through carrier, thefixed and moving portions of the axial LVOT, and the transducer and test-zone vent lines. The total test-too1­volume change due to these test-toQI components can be wrijten as:where:(0-1 )/).V tOOI/).V tCn/).V\\IDatQtal volume change due tQ test-tQol componentsvolume change due to tool component nvolume change attributable to tubingWith the exceptiQn of the transducer/vent lines, each of the test-tool components mentioned above can beassumed to behave as a thick-walled vessel under uniform external radial pressure and zero longitudinalpressure (i.e., the vessel is free to extend in the axial direction). The application of external pressure will cause177


the external radius of the vessel to decrease and the length of the vessel to increase. The component's volumechange attributable to an applied external pressure can be calculated as follows (Young, 1989):(0-2)and(0-3)where:r oM or jexternal radius of vesselchange in external radiusinternal radius of vesselP applied external pressureE modulus of elasticityv Poisson's ratioL length of vessel~L change in length of vesselTherefore,(0-4)The expansion or contraction of the transducer/vent tubing lines can be calculated assuming the lines are thickwalledvessels under uniform internal radial pressure where an increase in pressure causes the internal radiusof the tUbing to increase and the length to decrease. The appropriate formulae (Young, 1989) are as follows:(0-5)and~L - PVLtube [~]tube - E 2 2r o - rj(0-6)where:Therefore,~LlubeM jL tubochange in tubing length= change in internal radius of tUbing linestotal length of tubing(0-7)Changes in test-tool and tubing volume were calculated for each test-tool configuration used in the permeabilitytesting by applying Equations 0-2 through 0-4 for each tool component, and Equations 0-5 through 0-7 for all178


tubing. Component geometry data are found on test-tooI-installation diagrams and from field measurements.Values of E and v are found in Young (1989) and are listed below along with the associated materials:MaterialStainless SteelAluminumModulus ofElasticity (Pa)Poisson's Ratio1.93 x 10 110.276.90 X 10 10 0.30Total test-tool volume changes were determined by applying the equations for each tool component and tubinglength and summingthe cumulative volume change for a range of applied pressures encompassing the pressurevariation encountered during testing (0 to 15 MPa). Volume change versus applied pressure displayed anessentially linear relationship for this pressure range.Therefore:AV tOOI = C tool P(D-8)where:C tOOI= test-tool volume-change constantThe C toolconstants calculated for the tests analyzed in this report are as follows:TestC2H01-AC2H01-BC2H01-B(GZ)C2H01-CC2H02C2H02(GZ)C2H03N4P50L4P51-ASOP01SOP01(GZ)S1P71-ATool #MPT#1MPT#1MPT#1MPT#5MPT#4MPT#4MPT#5MPT #3, MPT #4MPT#3MPT#3MPT#3MPT#2C tool' Test-ToolVolume Constant0.250.250.200.440.090.090.080.090.080.080.140.08The test-tool volume constants indicate that volume changes due to the expansion and contraction of the testtool and the injection/withdrawal tUbing result in a maximum of about 30% or less of the total volumec.ompensation. The full effect of all volume-compensation factors is illustrated in the test-analysis figures inSection 7 that show model simulations with and without volume compensation.1).2 Borehole Compressibility.The three radial LVDTs on the multipackertesttools indicated that changes in radius occurred during the testingperiods. The radial-LVDT responses consistently indicated that the apparent borehole radius increased withincreased test-zone pressure, and decreased during the pressure reductions caused by the pulse withdrawals.Test-zone volume-compensation data were to be derived directly from the observed radial-LVDT responses,after adjusting the observed data for the radial expansion/compression of the radial-LVDT transducer carrier.However, during the compliance tests conducted in the steel and stainless-steel chambers (see Section 4.1),179


discrepancies were noted between the radial-LVOT data and the calculated response of the steel chamber. Theobserved LVOT displacement was 0.015 cm greater than the calculated chamber-wall expansion plus thecalculated test-tool compression. Figure 0-1 shows that the a-ring used to seal part of the radial-LVOT housingcould be subject to a maximumof 0.051-cmcompression with increasing external pressure on thetest tool duringshut-in and test conditions. The relative movement associated with a-ring compression would produce a radial­LVOT response indicating borehole expansion. Unfortunately, the actual magnitude of this movement duringtesting could not be quantified. As a result, the actual change in borehole radius could not be determined fromthe radial-LVOT data.Figure 0-2 is a plot of the test-zone pressure in L4P51-A along with the radius calculated from the radial-LVOTdata. Figure 0-2 shows that for approximately the first 90 days after borehole coring, the radius changesindicated by the LVOT data appeared to parallel changes in test-zone pressure. After approximately 90 days,however, when the radial-LVOT a-rings were presumably fully compressed, the radial-LVOT data indicatedborehole closure while the test-zone pressure remained relatively constant.The procedure used to quantify borehole-radius changes for volume compensation was based on the equationused to evaluate the effect of compression of the walls of an underground, pressurized cylindrical opening. Theequation used was that developed for a pressurized borehole in rock as given in Jaeger (1979, Sec. 10.3.2) asfollows:(0-9)where:M bchange in borehole radius due to applied pressureP applied internal borehole pressureC, rock compressibilityr b= initial borehole radiusv Poisson's ratioFor a typical borehole radius and a representative formation compressibility of 2.5 x 10- 11 Pa- 1 , the change inborehole radius was approximately 1.6 x 10- 4 crnlM Pa. Borehole-radius change yields a test-zane-volumechange as follows:(0-10)where:tN,adLtztest-zone-volume change due to change in borehole radiustest-zone lengthThe relationship between volume change and pressure can be approximated as:where:(0-11 )Crad = test-specific borehole-radius-change volume constantA rock compressibility of 2.5 x 10- 11 Pa- 1 , derived from data in Touloukian et al. (1981) and Krieg (1984), was usedto develop Crad foreachtest. The value of Poisson's ratio used inthe calculations was 0.25, a value representativeof Salado Formation halite (Krieg, 1984; Van Sambeek, 1987). The values of Crad developed for each testanalyzed in this report are as follows:180


METAL- TO-METALCONTACTNEW O-RING GROOVE WILL ALLOWPLUNGER ASSEMBLY TO SEAT ONSHOULDER WITH NO OFFSETI~~~r~~~~- :IE .051em MAXIMUM POSSIBLEIe CLOSURE DUE TO O-RINGCOMPRESSIONSINGLE BACK-UP RING. PARKER SEALS O-RINGSIZE NO 2-2120.35 em DIA CROSSSECTIONO-RING WILL FORMAROUND SCREWSPARKER SEALS O-RINGSIZE NO. 3-9110.30 em DIA CROSS SECTIONO-RING IS SHOWN DEFORMED TO ASHAPE OF APPROXIMATELY THE SAMEVOLUME. WITH MORE PRESSURE ITWILL FLATTEN OUT TO A LARGERDIAMETERNEWDESIGNOLDDESIGNFigure 0-1.New and Old Radlal-LVDT Design Showing Compressible O-Ring Seal


5 E~CO 5.31(J)c..::::l'6~(1jQ) a:....3 Q)::::l(J)"0(J)~Q) Q).... ....a...5.300CD-a-- Borehole Radius--0- Test-Zone Pressure-1 L.-...........---L....................L..........o.-..L...-..........L......I----".........---L............I--'--.o.-.a.-L-..........--I 5.29o 30 60 90 120 150 180 210 240to = 1989 291.5859Time Since Hole Cored (days)TR1-6344-646-0Figure 0-2. Test-Zone Pressure and Borehole Radius During L4P51-A Testing.Crad' BoreholeVolume ConstantC2H01-AC2H01-BC2H01-B(GZ)C2H01-CC2H02C2H02(GZ)C2H03N4P50L4P51-ASOP01SOP01(GZ)S1 P71-AMPT#1MPT#1MPT#1MPT#5MPT#4MPT#4MPT#5MPT #3, MPT #4MPT#3MPT#3MPT#3MPT#21.830.540.551.250.780.540.750.800.780.750.550.77These values of Crad represent average values for the lithologies in the different test boreholes. The values ofCrad indicate that the changes in borehole volume in response to changes in fluid pressure are the largest factorsin the total volume compensation used in the simulations of the individual tests. The full effect of all volumecompensation factors is illustrated in the test-analysis figures in Section 7.2 which show model simulations withand without volume compensation.0.3 Axial Test-Tool Movement.The multipacker test tools were retained in the test boreholes by bolting a steel tie-down bar or a square-tubesteel cross across the top of the tool mandrels, orby bolting a flange attached to the mandrels tothe 0.51-m long182


orehole collars which were cemented in place for every test borehole except C2H01 and 81 P71-A. However,while these fastening procedures were adequate for safety, they reduced but did not eliminate movement of thetest tool.The axial-LVOT responses indicated axial test-tool movement during all tests. This axial movement had twoapparent causes. First, the test tools appeared to exhibit piston-like behavior in response to pressure changesin the boreholes. The test tools moved slowly out of the boreholes during buildup periods, and retracted intothe boreholes at a much quicker rate during pulse withdrawals (Figure 0-3). This axial movement is thought tobe limited to the mandrel and other solid test-tool components. The packer element is not believed to actuallyslide in the hole, but to only flex slightly as the solid test-tool components move up or down in the hole. Thesecond factor that contributes to the apparent movement of the test tool is closure of rooms/drifts. As measuredby multipoint extensometers in the WIPP underground (e.g., Westinghouse, 1990), the relative motion causedby creep closure decreases with increasing distance from an excavation, causing boreholes drilled from theexcavation to elongate. With the tool anchored to the floor of the room/drift, room closure tends to pull the testtool away from the bottom of the borehole. On the time scale of the tests discussed in this report, room closureshould cause hole elongation at relatively constant rates of up to about one cm/yr (Westinghouse, 1990).Axial test-tool movement causes changes in the test-zone volume. The total volume change associated withaxial test-tool movement consists of packer intrusion/extrusion relative to the test zone, test-tool-bodymovement, and axial-LVOT actuator-rod movement. The volume change due to axial test-tool movement isillustrated in Figure 0-4, and is given by the following equation:~Vax = ~Vpacker + ~Vbody - L'lVactuator(0-12)where:~Vax~Vpacker~VbodYL'lVactuatorvolume change due to axial test-tool movementpacker intrusion/extrusion volume changetest-tooI-body volume changeaxial-LVOT actuator-rod volume changePackerintrusion into the test zone is difficultto express analytically without simplifying assumptions. The surfaceof the deformable packer element is assumed to form a straight line from the packer end-sub to the boreholewall. The packer element at the wall is assumed to be fixed at this point. Using these assumptions, as illustratedon Figure 0-4, the change in test-tool volume due to packer intrusion/extrusion and test-tool-body movementcan be combined and expressed as:(0-13)where:res packer end-sub radiusr b= borehole radius.1L ax = change in axial postlion of the test toolThe final term in Equation 0-12, ~Vactuator' is expressed as:~V = ~L 1t r 2actuator ax actuator(0-14)where:ractuatorradius ofaxial-LVOT actuator rod183


cu a..2.5~ 1.5Q)...::::JlJ)lJ)0.5Q)...a..E~ 0.1-r:::Q)0.0EQ)(.) -0.1ellc.. -0.2lJ)isl- e..Q.3..Q.4~ 290 330 370Test-Zone PressureAxial-LVDT Displacement4101989 Calendar Days450 490 530TRI-6344-647-QFigure 0-3.Test-Zone-Pressure and Axial-LVDT Data During L4P51-A Testing.If all test-specific constant values are substituted into Equations 0-13 and 0-14, Equation 0-12 can beexpressed as:(0-15)where:C axtest-specific axial test-tool-movement volume constantIn Equation 0-15, the borehole radius is considered to be constant because the minor changes in radiusdetermined from Equation 0-9 were determined to have a negligible influence on the calculated volume change!J.Vax'D.4 Test-Zone-Packer Deformation.The inflation pressures of the test- and guard-zone packers are monitored and recorded by the OAS duringpermeabilijy testing. The data show that the packer-inflation pressures do not remain constant throughout thetests. Figures 0-5 through 0-13 show the packer-inflation pressures during each test. Assuming that thepackers are not leaking, these changes in packer-inflation pressure indicate that the enclosed volume of thepacker must be changing. If the internal packervolume is changing, the external volume is most likely changing,which can be expected to affect the test-zone volume, and in turn, affect the test-zone compressibility.The packer-inflation-pressure responses indicate both transient and long-term behavior. In transient behavior,the packer reacts quickly to pressure events in the test zone such as pulse withdrawals and injections. A pulseinjection causes an increase in packer-inflation pressure while a withdrawal causes a decrease. Following anevent which changes the initial packer-inflation pressure, the packer-inflation pressure immediately changestoward the pre-event pressure. This type of behavior reflects the expected elastic properties of the packerelement.184


~ TEST-ZONE PACKER ELEMENTA X IAL ---""1LVDT HOUSINGwzoNr­ooj-tliVbOdy///~---+-------"" R ADIAL /LVDT's /////////////--BOREHOLEWALL1+--1'--_ A X IALLVDTAXIAL LVDTACTUATOR---1~----~RODwr-Figure 0-4. Test Zone and Axial LVOT Showing Elements Contributing to Volume Change.LVDTSPRINGAN D ------I'"f'---JPLUNGERASSEMBLY------------O-RINGSEALSL/i.Vactuator185


13.511.5'@' 9.5a..~Q)7.5....:::J(/)(/)Q)....a..5.5 r-3.51.5Test-ZonePulse~ InjectionsL~'10..~~~:h'I""l-L X~1-0-- Test-Zone Packer I-0- Guard-Zone PackerTest C2H01-A, Room C2~ .....--~ I-0.5~o 5 10 15 20 25 30to = 1988217.5464Time Since Hole Cored (days)TRI-6344-648-oFigure 0-5.Test- and Guard-Zone Packer-Inflation Pressures During C2H01-A Testing.'@'a..1612~-Q)8 ....:::J(/)(/)Q)....a..4~1-0--ITest-Zone Packer I-0- Guard-Zone Packer~~ ~ ~ \. ~ :L~.,:q 1i"""( I.... ~ ~:J........,-r~ ~~~TestC2H01-B, Room C2'1 I I Io o 25 50 75 100 125 150 175 200to - 1988 217.5466Time Since Hole Cored (days)TRI-6344-649-0Figure 0-6.Test- and Guard-Zone Packer-Inflation Pressures During C2H01-B Testing.186


141210~ a-Q)....::J(J)(J)Q)....a..642Test C2H01-C, Room C2--0- Test-Zone Packer-0- Guard-Zone Packer00 10203040506070ao90100to - 198944.4479Time Since Hole Cored (days)TRI-6344-650-0Figure 0-7.Test- and Guard-Zone Packer-Inflation Pressures During C2H01-C Testing.10rna..rnaa..~Q)....6::J(J)(J)Q)....a.. 42Test C2H02, Room C2--0- Test-Zone Packer-0- Guard-Zone Packer00 255075100125150175200225250275to - 1989107.3905Time Since Hole Cored (days)TRI-6344-651-0Figure 0-8.Test- and Guard-Zone Packer-Inflation Pressures During C2H02 Testing.187


COa..~12108~ 6::JenenQ)'-a.. 42~~~Test-Zone Packer-0- Guard-Zone PackerTest C2H03. Room C2I--o o 5 10 15 20 25 30 35 40to 2 1989 235.4200 Time Since Hole Cored (days)TRI-6344-652-0Figure 0-9.Test- and Guard-Zone Packer-Inflation PresslJres During C2H03 Testing.1513-U~trtl:m~~~ Removed Test Tool #3-0- Test-Zone Packer-


1210-0- Test-Zone Packer-0- Guard-Zone PackerTest l4P51-A, Room L4m e0..~


11.59.5--- Test-Zone Packer-0- Guard-Zone PackerTest 51 P71-A, Room 7, Waste Panel #1~ 7.5a..~(l).... 5.5::J(/)(/)(l)....a.. 3.51.5-0.50 204060 80 100 120140160180to = 1988 315.5~7Time Since Hole Cored (days)TR1-6344-656-0Figure 0-13.Test- and Guard-Zone Packer-Inflation Pressures During S1P71-A Testing.Long-term packer-inflation-pressure responses are more difficult to characterize and explain. In most of thepermeability tests, packer-inflation pressure continuously decreased during the majority of the test periods,although at a decreasing rate as the tests progressed. The decrease in packer-inflation pressure indicates thatthe packer volume is continually increasing, perhaps as a result of a creep-like behavior in the packer element.This behavior was confirmed by observing packer-pressure responses during compliance testing. Duringcompliance tests, 10 to 20% reductions in packer-inflation pressures typically occurred during the first 24 to 48hours after inflation. After increasing the packer-inflation pressures to compensate for these initial reductions,the continued reductions in packer-inflation pressures were significantly less.During some permeability tests, particularly in C2H01-B and C2H02, the relative changes in the test-zonepacker-inflation pressure were similar to the test-zone fluid-pressure responses, and the two pressures begantracking each otheras shown on Figures 0-14 (C2H01-C) and 0-15 (C2H02). Figure 0-14 shows that in C2H01­C, the test-zone pressure andthetest-zone-packer's inflation pressure synchronously increased and decreasedin response to zone pressure buildup and pulse withdrawals. The test-zone pressure and test-zone packerinflationpressure also increased together during an increase in the guard-zone-packer's inflation pressure onthe 23rd day after coring the test hole. Similar behavior was also observed in C2H02 during the latter part ofthe testing period, when the test-zone-packer's inflation pressure was about 1.5 MPa greaterthan the test-zonepressure. As shown on Figure 0-15, the test-zone-packer's inflation pressure began decreasing afterthe initialshut in, and then began increasing as the test-zone pressure began to build up. Both these tests exhibited testzonepressures of about 8 MPa, which is about twice the fluid pressure observed in the test and guard zonesof the other tests described in this report. Apparently, the lower pressure differentials between the test-zonepackers and the test zones in C2H01-C and C2H02 caused the test-zone-packers' inflations pressures to bemore sensitive to fluid-pressure changes in the test zones than during the other tests.The actual mechanism causing the synchronous pressure changes in the test-zone pressures and the testzone-packers'inflation pressures could be as follows. Decreases in test-zone pressure, as occurs during pulse190


13.511.59.5co c..~ 7.5Q)....::J


withdrawals, could decrease the external pressure on the packer element, causing an expansion of the packerelement and a consequent decrease in the packer's inflation pressure. Conversely, increases in the test-zonepressure would increase the external pressure onthe packer element, reducing the internal volume of the packerelement, thus causing an increase in the packer's inflation pressure. No evidence of leakage of test-zonepressure across the packer to the guard zone was observed in any of the tests.Expansion of the packer elements during pulse withdrawals implies that the volumes withdrawn duringthe pulsewithdrawals are greater than the volume changes in the test zones. Overestimates of the test-zone-volumechanges result in overestimates of test-zone compressibility as calculated by Equation 6-9. Inasmuch asdecreases in packer-inflation pressures were observed during all pulse withdrawals, all of the test-zonecompressibilityvalues presented in Table 6-3 may be slightly high.Apart from the parallel behavior of the test-zone and packer-inflation pressures observed during testing inC2H01-C and C2H02, the short- and long-term changes in packer-inflation pressure indicate that a "packercompressibilityfactor" may be important in the test analyses. Unfortunately, insufficient data are available toincorporate such a factor in the test analyses by means of a volume-change mechanism such as that discussedin Sections 0.1 through 0.3. The uncertainty in the specific internal volume of the packer systems used in eachtest, the quantity of entrapped gas either dissolved or present as a separate phase in the packers, the unknownnature of the elasticity of the packer elements, and the compressibility of the packer-inflation fluid make accuratedetermination of the changes in the internal volume of the packer system impossible.The permeability tests analyzed for this report were conducted with packers filled by direct inflation using anintensifier pump. No attempt was made to purge the packers of air orfluid before inflation. The air in the packersbefore inflation was probably entrapped during the inflation process. This air may have been dissolved in theinflation fluid after the pressure was raised to 8 to 12 MPa or may have still been present as a separate phase.The fluid volume usedto inflate a typical packer was measured to be 2330 ± 20 cm 3 . After observing a numberof compliance tests in the stainless-steel compliance-testing chamber, packer-inflation procedures weremodified to include complete draining and vacuum evacuation of the packers before inflating packers forpermeability-testing installations. Using these procedures, a typical packer inflation required approximately2650 cm 3 of fluid, about 300 cm 3 more than the amount required when the packerwas not completely evacuated.The absence of air, either as a separate phase or dissolved, probably reduces the compressibility of the packersystem. Data from compliance and permeability tests performed after using these packer-inflation procedureswill be presented in SUbsequent reports.Even if internal volume changes of a typical packer system could be determined exactly, the correlation betweenthe internal volume and external impact on the fluid-pressure responses of isolated test zones is problematic.For example, would a change in packer-inflation pressure resulting in a calculated 2 cm 3 increase in internalpacker-system volume yield a 1 cm 3 decrease in the test-zone volume and a 1 cm 3 decrease in the guard-zonevolume or would the change yield a 2 cm 3 decrease in the test-zone volume alone? The presence of a slidingend-sub on the test-zone packer further complicates volume determinations. The guard-zone end of the testzonepacker is designed to slide during packer inflation/deflation to reduce the amount of stretching of the packerelement. We do not know whether ornot movement ofthe sliding end-sub occurs at any othertime except duringpacker inflation.The compressibility of the synthetic material of the packer element is another potential component of packersystemcompressibility. However, because the packer-element compressibility is difficult to quantify, its effecton test-zone volume is also difficult to assess. The area of the packer element in contact with the test-zone fluidis approximately 43 cm 2 • The actual volume changes due to expansion or contraction of the packer-elementmaterial can only be determined through laboratory testing. The relatively small area of this material subject totest-zone pressure indicates that the effect of changes in the volume of packer-element material is likely to beinsignificant.192


0.5 Gas in the Test Zone.Gas was noted during some pulse withdrawals (Table 6-3). Four potential gas sources are: air entrapped inthe test-zone during test-tool installation; gas generated by the reaction of the metal tool components with thetest-zone brine; gas exsolved fromthe formation fluid underthe lower pressure inthe isolated borehole intervals;and gas generated by anaerobic bacterial degradation of possible hydrocarbons in the test-zone fluid.0.5.1 ENTRAPPED AIR.In C2H01-B, C2H02, SOP01, and S1 P71-A, a significant quantity of air may have been introduced into the testzone as a result of the test-tool installation procedures. To prevent the fluid displaced during test-tool installationfrom overflowing the top of the test tool and wetting the electrical elements in the test-tool mandrel, the test toolwas installed in a dry borehole and the packers were inflated. Brine was then pumped into the test and guardzones through the vent lines. The quantity of entrapped air was probably reduced in boreholes C2H01-B andSOP01 because the packers were deflated to adjust the test-tools' positions after filling the test and guard zones.After adjusting the test tools' positions, the packers were then re-inflated and the test and guard zones were shutin.The testing equipment and test-tool installation procedures for later tests were modified to reduce the possibilityof entrapped air. Specifically, these modiftcations were:1) the upper mandrel of the test tool was modified to be a sealed hollow tube to prevent overflow and entry ofborehole fluid;2) for vertically downward and downward-angled boreholes, the test boreholes are filled with fluid. and thatfluidis circulated through the transducer lines and vent lines before inflating the test-zone packerto ensure thatall air has been purged from these lines;3) drainagelfilling ports were added to the void spaces in the test-tool radial-LVDT connectors (SWivels) toensure that the void spaces in the swivel are filled with brine when the tool is installed in brine-filled boreholes;4) in horizontal or vertically upwards holes where the test zones cannot be filled with brine before packerinflation, the test zones are placed under vacuum pressure, the test-zone vent lines are extended from thefeed-through plug to the highest elevation possible, and the test zones are filled through the transducer linesuntil fluid flows from the vent lines;5) horizontally flat surfaces on the test tool were rounded to minimize the possibility of trapping air bubbles onthe test tool during test-tool installation.The effectiveness of 2) and 5) was Visually confirmed by installing the tool in a length of translucent PVC and/or LEXAN casing before and after these modifications and examining the surface of the test-zone portion of thetest tool to see where air bubbles had been eliminated by the modifications. This procedure was also used todetermine the optimum placement of the vent line for procedure 4).Including the effect of entrapped air in the test zone in the test analyses would require modification of the analysismodel to incorporate a non-linear two-phase boundary condition in the test zone. A simplified version of theboundary condition would assume that the fluid and gas phases were immiscible, while a more representativeimplementation would allow dissolving/exsolving of gas in the test-zone fluid.0.5.2 TOOL COMPONENT/BRINE REACTIONThe early versions of the multipacker test tool consisted of packers and LVDT carriers with stainless-steelcomponents and anodized aluminum end subs and spacers. When the test tools were removed from testboreholes after two to eight months of testing, the aluminum parts were observed to have undergone significantcorrosion. Corrosion of metals by brine in the absence of oxygen results in the production of metal oxides orhydroxides and hydrogen gas. A gas sample collected from the test zone of borehole C2H02 at the end oftesting193


was analyzed and found to contain 91% hydrogen (Saulnieret aI., 1991). Subsequently, aluminum componentsof the test tools were replaced with stainless steel, which exhibits much greater resistance to corrosion.The following table lists the materials used in the test tools for each test analyzed in this report and notes theseverity of corrosion indicated in the post-test examination of the test tools.~ ~ Material CorrosionC2H01-A MPT#1 SS NoneC2H01-B MPT#1 SS NoneC2H01-C MPT#5 AI,SS Minor AI PittingC2H02 MPT#4 AI,SS Severe AI PittingC2H03 MPT#5 SS NoneN4P50 MPT #3, MPT #4 AI,SS Minor AI PittingL4P51-A MPT#3 SS NoneSOP01 MPT#3 AI,SS Severe AI PittingS1 P71-A MPT#2 AI,SS AI PittingThe conversion to completely stainless steel test-tools should prevent gas generation by brine corrosion.However, if gas generation through brine/tool reaction continues to occur, the inclusion in the analysis modelof the effects of generated gas on the fluid-pressure responses would require modifying the analysis model toinclude both a method for including the effects of non-linear two-phase behavior in the test-zone, as discussedin D.5.1, and a time-varying gas-generation term.0.5.3 FORMATION GASGas dissolved in the formation fluid may be exsolving due to the reduced formation pore pressures in the vicinityof the borehole and in the test zone itself following drilling of the boreholes and/or pulse withdrawals. Few dataare available as to the dissolved gas content of in situ WIPP brines (Lappin et aI., 1989).If gas is being produced from the formation, gas introduced to the test zone will have a similar impact on testzonecompressibility as the other potential gas sources identified. However, unlike the other gas sources, theformation gas will also involve two-phase behavior in the formation and will require that the formation besimulated as a two-phase system. The presence of a free gas phase in the formation would cause testinterpretations to underestimate formation permeability when test-zone fluid-pressure responses are analyzedwith a single-phase model.Scoping calculations to address the possibility of formation-gas exsolution will be presented in subsequentreports. If the calculations indicate that two-phase behavior significantly affects the estimated formationpermeability, some of the tests in this report may be reanalyzed using a two-phase approach.0.5.4 BACTERIAL GAS PRODUCTIONGas could potentially be produced by anaerobic bacterial degradation of hydrocarbons in the test-zone brine.Experiments are currently being planned to assess the likelihood of this possibility, and to determine methodsfor reducing or eliminating bacterial gas production. If bacterial gas production cannot be eliminated, bacterialgas could potentially be included in future test analyses if the analysis model was modified as described inSection 0.5.1.0.6 Creep Closure.Halite and argillaceous halite are considered to undergo inelastic steady-state creep in underground openings(Krieg, 1984; Van Sambeek, 1987). Potential borehole-volume changes due to creep closure were evaluatedaccording to the rate equation:dv-=-A vdt C(D-16)194


where A cis the steady-state strain rate in the reference secondary creep law (Van Sambeek, 1987) or:-Q cA c = Ace RT 6.O'"c(0-17)where:A cQ cR6.0'n cTmaterial creep-law propertyapparent activation energy for steady-state creepuniversal gas constantdeviatoric stresscreep exponenttemperature of rockCreep closure was calculated for a typical test borehole in salt using the following values for the constants inEquation 0-17 (Senseny et aI., 1985):A c2 X 10- 3 MPa-"c/s6.0' 16 MPan c5.3Q c/R 9810 OKT303 oKThe calculations showed that creep-caused radius changes of from 0.01 to 0.06 mm, corresponding to volumechanges of 3.14 x 10- 4 to 1.13 x 10- 2 cm 3 /m, would occur after 120 days in a fluid-filled borehole pressurized to3 MPa. Changes significant enough to aijer test simulations would occur after several hundred days, or longerthan a typical permeability test. This amount of creep closure is much less than increases in volume that wereestimated for the compression of the test tool and borehole walls due to pressure buildup in the isolated testintervals. Therefore, a creep-closure term was not included in the volume compensation used in the testinterpretationsimulations. Measured creep closure will be included in future volume cOJillpensations as morereliable radial-LVOT data become available.195


REFERENCESJaeger, C. 1979. Rock Mechanics andEngineering, Second Edition (Cambridge: Cambridge University Press),523 pp.Krieg, A. D. 1984. Reference StratigraphyandRock Properties forthe Waste Isolation Pilot Plant(WIPP) Project,SAND83-1908 (Albuquerque, NM: Sandia National Laboratories).Lappin, A.A., Hunter, R.L., Garber, D.P., and Davies, P.B., editors. 1989. Systems Analysis, Long-TermRadionuclide Transport, and Dose Assessments, Waste Isolation Pilot Plant (WIPP), Southeastern NewMexico; March 1989, SAND89-0462 (Albuquerque, NM: Sandia National Laboratories).Saulnier, G.J., Jr., Domski, P.S., Palmer, J.B., Roberts, R.M., Stensrud, W.A., and Jensen, A.L. 1991. WIPPSalado Hydrology Program Data Report #1, SAN090-7000 (Albuquerque, NM: Sandia National Laboratories).Senseny, P.E., Pfeifle, T.W., and Mellegard, K.D. 1985. Constitutive Parameters for Salt and Nonsalt Rocksfrom the Oetten, G. Friemel, andZeeck We/ls in the Palo Duro Basin, Texas, BMI/ONWI-549 (Columbus, OH:Battelle Memorial Institute).Touloukian, Y.S., Judd, W.A., and Roy, R.F., editors. 1981. Physical Properties ofRocksandMinerals. McGraw­Hill/Cindas Data Series on Material Properties, Volume 11-2, 548 pp.Van Sambeek, L.L. 1987. Thermal and Thermomechanical Analyses of WIPP Shaft Seals, SAND87-7039(Albuquerque, NM: Sandia National Laboratories).Westinghouse Electric Corporation. 1990. Geotechnical Field Data andAnalysis Report, July 1988-June 1989,Volume /I, DOE/WIPP 90-006 (Carlsbad, NM: US DOE).Young, W.C. 1989. Roark's Formulas for Stress and Strain, Sixth Edition (New York: McGraw-Hili), 763 pp.196


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