Introduction to Borehole Observatories in ODP/IODP

Early ODPObservatory EffortsDating back to 1980‘s, there were twomain original ODP observatory efforts inparallel:OSN/ION broadband seismicobservatoriesCORK hydrogeological observatoriesSince the start of IODP, the purely OSNeffort has stalled, but a variety of CORKand related borehole observatories haveflourished. IODP borehole observatorydesigns now span a range of geophysical,geochemical, and microbiologicalobjectives.JR,19861994

CORK and OSN/ION Holes, 1991-2004

ODP CORK and OSN/ION Holes, 1991-2004OSN sites not (yet?)permanently instrumented

Two Primary CORK and Drilling Focus Regimes toDate:1. Ocean crust with thermally-driven fluid flow2. Subduction systems with compaction-driven flowJOIDES Hydrogeology PPG Report (2001)ODP/IODP have also made pioneering efforts to understand fluid flow incarbonate, gas hydrate, and overpressured passive margin settings.

Motivation: Hydrological Disruption via Open Reentry HolesBefore CORKs, open reentry holes often resulted in inadvertent flowperturbation experiments that yielded estimates of flow rates andpermeabilities but disrupted in-situ hydrogeological state and fluids.CORKs seal holes to stop flow + control perturbation -hence the acronym “Circulation Obviation Retrofit Kit”

Initial CORK ConceptThe 1989 dinner-napkinsketch by Earl Davis,Bobb Carson,Keir BeckerOriginal name:Instrumented BoreholeSealRenamed CORK in1991, for “CirculationObviation Retrofit Kit”

Original ODP CORK Hydrogeological ObservatoryMotivation: Seal reentry holes toprevent hydrological perturbation andallow reestablishment of in-situconditions, with capabilities for:• Long-term monitoring of T & P for• Background in-situ values• Hydrologic transients• Subsurface tidal loading effects• Transients of tectonic origin•••Sampling of formation fluidsActive hydrologic formation testingRecently, microbiological expts14 Original CORKs installed 1991-2001 in sedimented young oceaniccrust (shown) and subductionsettings.

Limitations of Original Design Multi-Zone ModelsWith only one seal at seafloor, signalsfrom entire open-hole or perforatedsection are averaged.For many cases, isolating multiplezones in a single hole would yieldmuch more representative results.Starting in 1999, three multi-zoneCORK models have been developed,all utilizing downhole packers:• “Advanced CORK” or ACORK• “Wireline CORK”• “CORK-II”14 multi-zone CORKs installed 2001 -2011 in sedimented young ocean crustand subduction settings.Advanced CORK Workshop (1998)

Evolution of CORK Designs, 1991-2011From single-seal original CORK to multi-seal ACORK and CORK-IIto downhole single-seal memory “Smart Plug” and “Genius Plug”...Original CORKAdvanced CORKData loggerCORK IIData loggerSamplingportsSamplingportsData loggerSmart PlugRe-entryconeRe-entryconeSea floorSea floorSea floorSea floorSeal16" casing Seal16" casing Seal16" casingSealStandard 10 3/4"casingHydraulicconduits10 3/4" casing Standard10 3/4" casingThermistorcableGroutMultipletool stringReamedLWD holePackerPackerPackerZone AhydraulicsamplingportZone BhydraulicsamplingportZone ChydraulicsamplingportZone AZone BZoneCReamedLWD holeMultipletool stringPackerPacker4 Ω” linerZone AZone BRecoverablebridge plugMonitoringinstrumentStandard 10 3/4"casingGroutFluidsamplerUncased9 7/8"RCB holeUncased9 7/8"RCB holeSeismometer andstrain gaugeUncased9 7/8"RCB holeGrout

Componentsfor multi-levelpressuremonitoringand fluidsamplingAt wellhead:absolute pressure sensors,PPB digitizers, T sensors,power, data storage,and pressure line control valvesOutside sealed casing:permeable filterscreensPressure transmissionfrom screens to seafloorvia hydraulic tubing12

CORK components deployed inside or below casingWellheadconnections:electrical, pressure,flow, and inside-casingaccessSeismometer, tilt meterin or below casingThermistorsinside, outside,or below casingStrainmeterbelow casing13

Fluid Sampling via CORKs (I)Original CORK design incorporated1/2” teflon tubing running fromformation to valves on the wellhead,but this did not work well.Major improvement: development ofself-contained OsmoSamplers installedon the sensor string and recoveredyears later.Latest multi-zone “CORK-II” and“CORK-Lite” designs incorporatecapability to deploy OsmoSamplers forfluid geochemical and microbiologicalobjectives both deep in sealed holesand at wellhead valves with access toin-situ fluids via small-diameter tubing.

Fluid Sampling via CORKs (II)When the formation is overpressured and transmissive, as at somesediment-buried basement highs in young crust, then sampling viathe CORK valve is promising.PrototypeCowen/Johsonmicrobiologicalsampler at Hole1026B. SeeCowen et al,Nature (2003)for results.

CORK-II System as onIODP Exps. 327, 336 -Current “Standard” Modelfor Basement Holes•Four nested casing strings, withmultiple sealing systemsMultiple monitoring levels withinflatable + swellable packersTubing umbilical from formation toseafloor, bringing pressure and fluidsto wellhead gauges and samplersFree-flow valve for producing holeMultiple sensors/samplerssuspended in hole:••••••Memory temperature loggersFluid/gas “OsmoSamplers”Microbiological experiments•

2011 ROV Fly-Around, Hole 1362A CORK-IICourtesy A. Fisher, S.Video Courtesy Andy Fisher

CORKs: Submersible Support from National FundingAgencies (e.g., NSF, JAMSTEC,…)CORKs require submersible servicingon ~2-3 yr intervals (data download,battery or instrument exchanges).• Alvin: 1991, 1993-1995, 1997-2002,2004-2009• Jason/Jason II: 1998, 2003, 2010-2012• MPL Control Vehicle: 1999, 2001• ROPOS: 1992, 2004, 2010, 2011• Nautile: 1995, 1998• Kaiko-10k: 2002, 2003• Kaiko-7k: 2006-2009, 2011, 2012• HyperDophin, 2009• Shinkai 6500: 2004

•••CORK Funding Model(s)Red/orange = CORK‘infrastructure’ traditionally fundedby ODP/IODP.Blue = Scientific instrumentationnormally funded by nationalagencies (e.g., NSF, GSC, IFREMER,JAMSTEC) based on regularresearch proposals.Submersible servicing operationsalso require funding from agenciesbased on research proposals.•Funding model was extended by

New Observatory Concepts for Future -“Earth in Motion” Theme of New Science Plan• NanTroSEIZE Smart Plug and Riser-Hole Monitoring System (right)• “Seis-CORK” with seismometers• Simpler pressure-only “S-CORK” asproxy for crustal strain• SCIMPI (Simple Cabled Instrumentto Measure Parameters In-situ) forupper sediments (~200-300m)• Linking to shore with seafloor cables- several CORKs connected orscheduled to connect to NeptuneCanada cable in 2009-2012• CORK-Lite for legacy reentry holes• Observatories deployed withseafloor drill systems (BGS, MEBO...)NanTroSEIZE Phase 3 20underway in Japan for a seafloor fiber-optic cable network in the Kumano region for geodetic(A-GPS) and seismic monitoring; we are coordinating efforts with that group so that, if it isconstructed, the borehole will be tied in for real-time data transmission. Otherwise, periodic datadownload from the wellhead through ROVs/submersibles or telemetry will be required. In anycase, the seafloor network if built will provide much of the broader distributed geophysicalcontext for addressing our goals, outside of IODP efforts.SeismometryFigure 9. Conceptual drilling andinstrumentation plan proposed forNT3-01A. Drilling would proceedwith a mix of LWD and coring withcasing to total depth, followed bysidetracking to core the prime faulttargets and install monitoringinstrumentation. Sensors shown arepositioned schematically. A numberof sensor elements are not shownfor clarity, including fiber opticthermistor arrays and fluidpressure lines. Packers isolateperforated zones for fluidcommunication to the formationabove, below, and inside each of the2 target fault zones. Depths arebased on Line 5 in figure 2, butborehole deviation is not to scale.Seismological data will be collected during both the drilling and monitoring stages of thePhase 3 project. These experiments will include Vertical Seismic Profiles (VSPs), a vertical

Wireline CORK + CORK-LiteWireline CORK (right) installed withMPL Control Vehicle in Hole 504B(Becker et al, EPSL, 2004).CORK-Lite (below) installed 2012 withROV Jason in Hole 1383B (Wheat etal, S.D. in press).504BCORK-Lite1383B!

An opportunistic approach:Strapped-on screens and hydraulic lines22

Borehole Observatories Connected to Shore by CablesJuan de Fuca Hole 1026BCORK installed 1996CORK-II installed 2004NEPTUNE-connected 2009Next:Nankai C0002 (Donet)Cascadia 1364A and JFR1027, 1362 (NEPTUNE)23