Mass Transfer & Porous Media (MTPM) - Andra

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P/<strong>MTPM</strong>/29Figure 1: A. Scheme of the gas permeability measurement B. Gas permeability in function of loadingunloadingaxial stress.difference of applied gas pressure is low (less than 0.5 MPa). Accurate measurements on sample weightand ceramic porous stone weight have been taken and simulations on the mechanism agree withexperimental results. The lost weight of pore water relative to the initial weight of pore water is little. Itshows that a) the desiccation of sample is negligible in triaxial cell test conditions b) the final change ofwater content is not linked to water vapour flow exchanges between gas flow and pore water c) it is relatedto an induced convective flow of liquid pore.We want also highlight result of one of the tests where the sample was fractured during the loading phase.The origin of the rupture is an artefact of the sample ant it is not related to its mechanical behaviour. Themeasurement of axial strain allows identifying the rupture event during the test, but this is not possible byanalyzing permeability measurements. This shows that under the used confining pressure (11 MPa), evenif fracture network is continuous form one face to the other, flow of gas is not dramatically increased. Onecan conclude that closure of fractures under in situ mean stress doesn’t change the global gas permeabilityof samples with in-situ water content.Further investigations are necessary for more complete measurements of effective gas permeability ofwetted samples by fixing the initial water saturation of samples over large range of saturations.ReferenceW.F.Brace, J.B.Walsh, W.T.Frangos, Permeability of granite under high pressure, J.Geophys. Res.73 (2)(1968) 2225-2236.P.A.Hsieh, J.V.Tracy, C.E.Neuzil, J.D.Bredehoeft, S.E.Silliman, A transient laboratory method fordetermining the hydraulic properties of ‘tight’ rock. I. Theory, Int.J.Rock Mech. Min. Sci & Geomech.Abstr. Vol. 18 (1981) 245-252.H.J.SUTHERLAND S.P.CAVE, argon gas permeability of New Mexico Rock Salt under HydrostaticCompression. Int.J.Rock Mech.Min.Sci&Geomech.Abstr. Vol.17 (1980) 281-288.Page 480INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENT
P/<strong>MTPM</strong>/30GAS INTRUSION IN SATURATEDBENTONITE – A THERMODYNAMICAPPROACHMartin Birgersson, Mattias Åkesson, Harald HökmarkClay Technology AB, Ideon Research Centre Lund, SwedenA thermodynamic description of the response of a saturated bentonite system to changes in externalvariables has successfully been adopted in several different cases. Examples include correspondencebetween swelling pressure and water retention properties of unconfined bentonite ( Bucher and Müller-Vonmoos, 1989), pressure response due to changes in salt concentration of an external solution(Karnland et al., 2005) and the description of the behavior of confined bentonite below 0˚C. In thepresent work the same thermodynamic framework is used as a starting point for describing gasintrusion in saturated bentonite.The response to changes in external variables (water pressure, gas pressure, temperature, salinity etc) of aconfined bentonite system penetrable to water is a matter of equalization of the chemical potentials of waterin the clay and water external to the system. The chemical potential of clay water under isothermalconditions and without added solutes isµ clay( w) = µ 0 + RT ln RHunconf.( w)+ P⋅v wWhere µ 0 is a reference chemical potential for bulk water in equilibrium with its vapor pressure atthe considered temperature, RHunconf. ( w ) is a function describing equilibrium relative humidity forthe unconfined clay with water content. Here the molar volume of clay water is assumed to be equalto the bulk value, v w , and independent of pressure.A homogenous, isotropic model of bentonite is presented which is completely defined by the curveRHunconf. ( w ) , and the water content at saturation, w sat . Total pressure at equilibrium in this model iswhereP g > 0⎧ ⎪ Ps+ Pl, saturatedPTOT( Pg, P l)= ⎨⎩⎪ Pg, unsaturatedRTP s =− ln RH ( w sat ) ,v wis gas pressure and the chemical potential of external water isµ = µ 0 + Pl⋅ v w,which defines liquid pressure, P l , when µ − µ 0 < 0 . The criterion for saturation is PS > Pg −Pl≡ s ,where s denotes suction.It should be noted that the present model is based on thermodynamic equilibrium in a rather strict sensewhich is not achieved in experiments where the initial state is unsaturated. E.g. the stress build-up in ainfiltration test do not follow the equation for total pressure from above. On the other hand, it can be arguedbased on experimental facts that the model is relevant to adopt when describing gas entry events, wherethe initial state is a water-saturated system.INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENTPage 481
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Poster [MTPM]Mass Transfer & Porous
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P/MTPM/1The free energy cost of for
Page 7 and 8:
P/MTPM/3DIFFUSION OF IONS IN UNSATU
Page 9: P/MTPM/4POROUS MEDIA CHARACTERIZATI
Page 12 and 13: P/MTPM/5Oxalate ionsQuartzQuartz +P
Page 14 and 15: P/MTPM/6borehole was capped with a
Page 16 and 17: P/MTPM/7Initial state with glass an
Page 18 and 19: P/MTPM/8The mesh of the elementary
Page 20 and 21: P/MTPM/9Moreover, using another sam
Page 22 and 23: P/MTPM/10Figure 1: Horizontal cross
Page 24 and 25: P/MTPM/11n t (mol)as received8 10 -
Page 26 and 27: P/MTPM/1210,9Degree of saturation (
Page 28 and 29: P/MTPM/13RESULTSFirst, we estimated
Page 30 and 31: P/MTPM/142.5Energy (M eV)1.6 1.7 1.
Page 32 and 33: P/MTPM/15C/Co10.90.80.70.60.50.40.3
Page 34 and 35: P/MTPM/16ModelIrmayvG-M1vG-M2vG-M3T
Page 36 and 37: P/MTPM/17Figure 1: Experimental HTO
Page 38 and 39: P/MTPM/18Diffusion experiments were
Page 40 and 41: P/MTPM/19Figure 1: Used mesh for co
Page 42 and 43: P/MTPM/201.81.61.41.2upstream compa
Page 44 and 45: P/MTPM/21490Pressure [bar]0 10 20 3
Page 46 and 47: 134P/MTPM/22through-diffusion exper
Page 48 and 49: P/MTPM/23HA (µg/g)3002001000(a):pH
Page 50 and 51: P/MTPM/24through each sample. The p
Page 52 and 53: P/MTPM/25FIRST RESULTSPreliminary c
Page 54 and 55: P/MTPM/26heterogeneous distribution
Page 56 and 57: P/MTPM/27Relative concentration (C-
Page 58 and 59: P/MTPM/280.75m0.25mTable 1: Cross s
Page 62 and 63: P/MTPM/30The presented theory is ex
Page 64 and 65: P/MTPM/31Furthermore, Van Loon et a
Page 66 and 67: P/MTPM/32RESULTSResults show that,
Page 68 and 69: P/MTPM/33Clay modellingPore size di
Page 70 and 71: P/MTPM/341.60E-11f H2-d total (kg.m
Page 72 and 73: P/MTPM/350.50η R ()0.400.300.200.1
Page 74 and 75: P/MTPM/36200Bq/g1801601401201008060
Page 76 and 77: P/MTPM/37Argilite (ionic strength 0
Page 78 and 79: P/MTPM/38-Samples cored at 12m were
Page 80 and 81: P/MTPM/39APPLICATIONSCORE 2D has be
Page 82 and 83: P/MTPM/40Figure 1: Sketch drawing o
Page 84 and 85: P/MTPM/41Figure 1: Thermal conducti
Page 86 and 87: P/MTPM/42Figure 2: Model of pore st
Page 88 and 89: P/MTPM/43The available data are con
Page 90 and 91: P/MTPM/44Figure 1: Spatial extensio
Page 92 and 93: P/MTPM/45Relative concentration / (
Page 94 and 95: P/MTPM/46Figure 2: Swelling pressur
Page 96 and 97: P/MTPM/47then used in the transport
Page 98: P/MTPM/4820181614121086Gas pressure
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