DOE Award No.: FP00003995

Final Project Scientific / Technical Report

PROPERTIES OF SEDIMENTS CONTAINING METHANE HYDRATE, WATER, AND GAS SUBJECTED TO CHANGING GAS COMPOSITIONS

Project Period (May 1, 2016 to September 30, 2018)

Submitted by: Timothy J. Kneafsey

_____________________________________

Signature

Lawrence Berkeley National Laboratory DUNS #:xxxxxxx

1 Cyclotron Road Berkeley CA 94720

Email: tjkneafsey@lbl.gov Phone number: (510) 486-4414

Prepared for:

United States Department of Energy National Energy Technology Laboratory

OIL & GAS

November 26, 2018

Office of Fossil Energy

DISCLAIMER

“This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.”

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ProjectSummaryReport

LBNL-KIGAMCollaborationintheInvestigationoftheGasProductionPotentialofHydrateDepositsintheKoreanEastSea

Submittedtothe

KoreaInstituteofGeoscienceandMineralResources(KIGAM)

and

NationalEnergyTechnologyLaboratory(NETL)

by

LawrenceBerkeleyNationalLaboratory(LBNL)

EnergyGeosciencesDivision

1CyclotronRd.

Berkeley,California94720

USA

PrincipalInvestigator:TimothyJ.Kneafsey

Co-PI:GeorgeJ.Moridis

Co-PI:MatthewT.Reagan

WithcontributionfromJihoonKim(TAMU)

September30,2018

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Executive Summary ThisreportsummarizesactivitiescarriedoutintheprojectentitledLBNL-KIGAMCollaborationintheInvestigationoftheGasProductionPotentialofHydrateDepositsintheKoreanEastSea.ProjectperformersincluderesearchersatLawrenceBerkeleyNationalLaboratoryandTexasA&MUniversity.ThisreportdiscussestwogroupsoftaskshavingthegoalofimprovingunderstandingofthefutureproductionofmethanefromhydratedepositsintheUlleungBasin(UB).Thefirstgroupoftasksarenumerical,performedusingTOUGH+HYDRATEandothercodesdevelopedatLawrenceBerkeleyNationalLaboratory.Thesecondgroupoftasksareexperimental,performedinlaboratoriesatLawrenceBerkeleyNationalLaboratory.AlltaskswereperformedincollaborationwithorwithinputsfromKIGAM.CodeDevelopmentandSimulationTobettersimulatehydrate-relatedbehaviorrelevanttotestingandproductionofgasfromtheUlleungBasin,thecapabilitiesoftheT+H/pT+Hcodesrequiredenhancementsthroughtheadditionalofseveralnon-Darcyfloweffects.ItisimportanttonotethatthenewsimulationcapabilitiesleveragedrecentNETL-fundedworkoncoupledT-H-Msimulationofshalegasandshaleoilsystems.NumerousenhancementsweremadetotheTOUGH+HYDRATEcode(T+H),andthesehavebeendescribedinajournalpaper.UsingT+H+Millstoneandthewellboremodel,theLBNLteamconductedsimulationsofgasproductionsandtheassociatedgeomechanicalsystemresponseduringgasproductionfromhydratesattheUlleungbasinusingthemostrecentgeologicalmodelandtheflow,andgeomechanicalpropertiesprovidedbyKIGAMresearchers.TheseresultshavebeensubmittedasapapertoJ.Pet.Sci.Eng.OurteammateatTexasA&MUniversitysuccessfullysimulatedthebehaviorofcoupledflowandgeomechanicsatUBGH2-6.Consideringmoreaccurateaxisymmetricformulation,thesameconclusionasinthepreviousstudy-thatthewellboremightnotbestable,whichcansufferfromsignificantverticalslip–wasobtained.Thus,carefulconsiderationofgeomechanicsbehaviorisrequired.Currently,moresimulationwithvariousproductionscenariosandfurtherin-depthanalysisareongoingtoinvestigategeomechanicalbehaviorsuchassubsidence,evolutionofeffectivestress,andanypotentialofgeologicalfailureincludingwellborecollapse.

LaboratorystudiesTwostudieswereperformedtopartiallyaddresstheessentialquestion:Cangasbeeffectivelyproducedfromthelayeredsand/mudsystem?Theseincludestudiesofparticletransportinsand/mudlayeredsystems,andhydratedissociationtestsin

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sand/mudsystemsatdifferentratestomodeldifferentflowsresultingfromproductionmethodsanddistancefromthewell.

Inourstudiesunderrelevanteffectivestressesinthesand/mudandsandparticlesystemsinvestigated,particlemigrationincludingkaoliniteparticles,diatoms,andmicron-scalebariteparticleswasnotgeomechanicallysignificant.Geomechanicalsystemfailurewasfrequentlyobservedwhensandcontrolwaspoor.Productionofmudalsooccurred,butparticletransportthroughthesandlayerwasminimal.Thetestsdidnotcovereveryforeseeablecondition,however,andtheseresultsareincontrastwithseveralotherstudies.

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Table of Contents

LBNL-KIGAMCollaborationintheInvestigationoftheGasProductionPotentialofHydrateDepositsintheKoreanEastSea..........................................................................1

ExecutiveSummary........................................................................................................................2

ProjectDescription.........................................................................................................................5

Task1: Enhancedflowsimulationcapabilitiesforthesimulationofcomplexmud/silt/sandhydrate-bearingsystems...............................................................................6

Task2: EnhancedgeomechanicalcapabilitiesforthepredictivesimulationofpotentialUBGHfieldtestsites(fundedbyKIGAM)..........................................................10

Task3: ProjectManagement,Communication,ReportingandTechnologyTransfer(fundedbyUSDOE)...................................................................................................18

Task4: Gasproductionfromasandlayerinasand/mudlayeredsystem..........19Task5: Mechanicalandchemicalbehaviorofdiatomaceousmediumandfiltrationbehaviorofsand………………….…………………………………………………………….35

LBNL-KIGAMCollaborationintheInvestigationoftheGasProductionPotentialofHydrateDepositsintheKoreanEastSea.......................................................................42

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Project Description This report presents the results of five tasks performed to support investigation into the potential field test and gas production from layered sands and muds as found in the Ulleung Basin. Knowledge gained from this work will benefit KIGAM and USDOE in their consideration of natural gas production from suboceanic deposits containing methane hydrate. The five tasks include improvements to hydrate multiphase flow simulators that include geomechanical modeling, and simulations of test cases of interest. Laboratory tasks investigating the behavior of hydrate-bearing layered sand/mud systems, and particle transport in these systems were performed. The tasks are: Task1: Enhanced flow simulation capabilities for the simulation of complex

mud/silt/sandhydrate-bearingsystemsSubtask1.1:Non-DarcycapabilitiesforT+HcodesSubtask1.2:Simulationofcomplexmud/silt/sanddeposits

Task2: EnhancedgeomechanicalcapabilitiesforthepredictivesimulationofpotentialUBGHfieldtestsites

Task3: Project Management, Communication, Reporting and TechnologyTransfer

Task4: Gasproductionfromasandlayerinasand/mudlayeredsystemTask5: Mechanical and chemical behavior of diatomaceous medium and

filtrationbehaviorofsand

TheworkwasperformedoverthetimeperiodofMay2017toSeptember2018.Althoughoriginallytheprojectwastostartearlier,contractingandfundingissuesdelayedtheprojectstart.Eachtaskispresentedindividuallybelow.Journalpapersthatwerepartiallyfundedunderthisprojectareincludedasattachments,andnotfurthersummarizedherein.

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Task 1: Enhanced flow simulation capabilities for the simulation of complex mud/silt/sand hydrate-bearing systems

GeorgeMoridis,MattReaganSubtask1.1:Non-DarcycapabilitiesforT+Hcodes(LBNLportion-fundedbyUSDOE)Subtask1.2:Simulationofcomplexmud/silt/sanddeposits(fundedbyUSDOE)

TheTOUGH+HYDRATEcode(T+H)receivedextensivephysicalpropertiesupgrades,non-Darcyflowcapabilities,andworkflowenhancements.T+Hnowincludesseveralnewphysicalpropertiesrelationships:1. Newwaterpropertiesformulations(IAPWS,2008to2014)2. Newgasviscosityestimationoption:Frictiontheory(Quinones[2000])3. NewadditiontothegasEOSoptions:Lee-Kessler(1975),newdefaultfor

hydrocarbongasenthalpy4. Newmethodsforcomputinghydratethermophysicalproperties:Data-Gupta

(2008);Ballard(2011)5. Newactivity-basedoptionstodeterminegassolubilityinH2Oinadditionto

standardHenry’slaw6. Newcapabilitiestofullyaccountfortheeffectsofhighsalinityonhydrate

formationTheT+Hcodehasalsobeenexpandedbytheinclusionofnon-Darcyflowcapabilities,includingturbulentflowandgas-slippageeffects(wheneffectivepermeabilitiesarebelowthemicro-Darcylevel)coveringthespectrumfromKlinkenbergflowtoKnudsendiffusion(Maleketal.,2003).Thedrift-fluxmodel(Shietal.,2005)hasbeenincorporatedintothecodeforthesimulationofcoupledwellboreinteractions,andForchheimerflowhasbeenaddedtohandlehighfluidvelocitiesinhigh-permeabilitymedia(Barree,andConway,2004).Workflowenhancementstothecodeincludetime-variableboundaryconditions,monitoringof3Dregionsofvaryingshapes,monitoringofflowthroughuser-defined2Dand3Dinterfaces,andnewoutputformats(conversiontoVTKandsilofiles).ThelatestversionofT+HwasreleasedinJanuary2018anddocumentedinthefollowingpaper:Moridis,G.J.,Queiruga,A.F.,Reagan,M.T.,“TheT+H+MCodefortheAnalysisof

CoupledFlow,Thermal,ChemicalandGeomechanicalProcessesinHydrate-BearingGeologicMedia,”Proc.9thInt.ConferenceonGasHydrates,Denver,CO,1-3June2017.

WehavealsocompleteddevelopmentofthelatestT+MsimulatorbycouplingthelatestT+HsimulatortoMillstone,anewgeomechanicalcodethatoffersnew

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abilitiesandfixesmanycomputationalandmathematicalshortcomingsofearliercodesusedtodescribethegeomechanicalresponseofhydrate-bearingsystems.Thenewformulationincludestheabilitytoperformgeomechanicalsimulationswith2Dradiallysymmetricmeshestorepresent3Dverticalwellproblem,increasingnumericalefficiency.ThenewT+H/Millstoneplatformisdescribedinarecentlysubmittedpaper:Moridis,G.J.,Reagan,M.T.,Queiruga,A.F.,“TheTOUGH+MillstoneCodeforthe

AnalysisofCoupledFlow,Thermal,ChemicalandGeomechanicalProcessesinHydrate-BearingGeologicMedia,PartI:TheHydrateSimulator,”submittedtoTransportinPorousMedia.

UsingT+H+Millstoneandthewellboremodel,theLBNLteamhasbeenconductingsimulationofgasproductionsoftheassociatedgeomechanicalsystemresponseduringgasproductionfromhydratesattheUlleungbasinusingthemostrecentgeologicalmodelandtheflowandgeomechanicalpropertiesprovidedbyKIGAMresearchers.ThecoupledMillstonecodeallowsforseparateflowandmechanicsmeshes,resultingingreaternumericalefficiency(Figure1.1).Thesimulationsconsideredlarge-deformationgeomechanics(notfullyconsideredinearlierstudies)andplasticity.Thenew,moreefficientformulationofMillstone,whichusesanaxisymmetric/cylindrical2Dmodelinsteadofa3Dwedge,issubstantiallymorephysicallyandnumericallyaccurateindescribingthenear-wellregionaroundaverticalwellandalsocomputationallymoreefficient.Thus,someearliersimulationswerere-runusingthenewcode..

Figure1.1.DomainoftheflowproblemasaTOUGH+meshdomain(black,centered)

insetinalargergeomechanicaldomainwithafiniteelementmeshsolvedbyMillstone(blue,cuthalfwaywithextentoutlined).

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Inaddition,usinganewpost-processingcapabilityforcouplingflowandgeomechanics,werevisitedearliersimulations(documentedina2016report)andperformeda1-waycouplingofthe2016productionsimulationresultstothenewMillstonegeomechanicalsimulatorusingthetough-convertanalysispackage.

Figure1.2.CasekfS: Hydratesaturation(SH)distributionsonthex-zplaneaty=40

mduringthe14-daylongproductiontest(Pw=9MPa). Thesimulationresultsshowthat:1. Thegasreleaseandproductionratesaregenerallylowandtheaffectedregionof

thereservoirislimited(Figure1.2).2. Thewaterproductionaccompanyinggasproductionfromthisdepositappears

manageable(intermsofabsoluteratesandvolumes)underallthescenariosinvestigatedinthisstudy;however,inrelativetermsthewater-to-gasratioisveryhighduringthe14-dayproductiontestandstabilizesrelativelyearly.

3. Themaximumsubsidenceattheseafloorispredictedtobe0.016m,butthemaximumsubsidenceandupliftofthetopandbottomofthereservoir,respectively,ispredictedtohaveamagnitudeof0.22m(Figure1.3).

4. Reservoirheterogeneitydecreasesthemagnitudeofthegeomechanicalresponse.

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Figure1.3:Verticaldisplacementhistoryofthesystemofbothcasesattheseafloor(z=0m),topofthereservoir(z=-140m),andbottomofthereservoir(z=-153m).ThenewresultsweresubmittedasapapertoJ.Pet.Sci.Eng.:Moridis,G.J.,Reagan,M.T.,Queiruga,A.F.,Kim,S.-J.“SystemResponsetoGasProductionfromaHeterogeneousHydrateAccumulationattheUBGH2-6SiteintheUlleungBasinoftheKoreanEastSea,”inpress,J.Pet.Sci.Eng.

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Task 2: Enhanced geomechanical capabilities for the predictive simulation of potential UBGH field test sites (funded by KIGAM)

JihoonKim(TexasA&MUniversity)NumericalinvestigationofdepressurizationandgasproductionatUBGH2-6:Coupledflow-geomechanicssimulation

Introduction

Weemploytheaxisymmetricdomainofsimulation,consideringgasproductionwithaverticalwell.Inthepreviousstudy,thegeomechanicsdomaindidnotfullyfollowtheformulationofaxisymmetricgeomechanics.Inotherwords,weusedtheCartesiancoordinatesystemforthegeomechanicsproblem,whichFLAC3Donlyallows,wherethegeomechanicsdomainwaslikeasliceofapie.Asaresult,inaccuracynearthewellareamightexist.Inthisstudy,wetaketheexactformulationofaxisymmetricgeomechanicsinordertohavemoreaccurateresults.Precisely,wetakethecylindricalcoordinatesystemofstressandmomentumbalancetocalculatedeformationandstressnearthewellboreappropriately.Also,weuseanin-housesimulatorofcoupledflowandgeomechanics(TOUGH+Hydrate-ROCMECH),whileT-F(TOUGH+Hydrate-FLAC3D)wasusedinthepreviousstudy.

Fromnumericalresults,forlongproductionofdepressurization,weidentifysmallsubsidenceatthesurfacebutsignificantverticaldisplacementabovethehydratezones.Thus,asfoundinthepreviousstudy,carefulconsiderationforwellborestabilityisrequired.

Numericalsimulation

ThesiteofUBGH2-6islocatedneartheseafloorintheEastSea,SouthKorea,havingsignificantoverburdeninthedeepsea(Figure2.1).Thehydratezoneconsistsofalternatinghydrate-bearingsandandmudlayers.AsshownintherightofFigure2.1,wetakethedomainof250mby220mfornumericalsimulation,whichhasirregularsizesofgridblocks(160by140).Inparticular,wehavesmallgridblocksneartheverticalwellandthehydratezone.

Theinitialpressuresatthetopandbottomare23.1MPaand24.59MPa,respectively,andtheinitialtemperaturesatthetopandbottomare6.366oCand18.633oC,respectively.Theyaredistributedlinearlyfromtoptobottom.Theinitialhydratesaturationinthehydratezoneis0.65,whileitiszerointheotherzones.Theinitialverticalandhorizontalstressesare-23.1MPaand-3.47MPa,respectively,andtheyaredistributedverticallywiththegradientsof-25.0kPaand-3.47kPa.Tensilestressispositive.Table2.1showsthemainpropertiesofflowandgeomechanicssimulation.Weproducegasbydepressurization,applyingtheconstantbottomholepressureof9MPa.

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Figure2.1Left:geologicalinformationofUBGH2-6Right:discretizeddomainforflow

Table2.1.Materialpropertiesforflowandgeomechanics

Property Overburden Hydratelayer Mud-Interlayer

Underburden

Drainedbulkmodulus,SH=0%

15.55MPa 27MPa 20MPa 22MPa

Drainedshearmodulus,SH=0%

5.185MPa 16MPa 6.667MPa 7.407MPa

Drainedbulkmodulus,SH=100%

285MPa 933.33MPa 285MPa285MPa

Drainedshearmodulus,SH=100%

99.75MPa 560MPa 99.75MPa 99.75MPa

Permeability,SH=0% 0.02mD 500mD 0.14mD 0.02mD

Initialporosity 0.76 0.45 0.67 0.0

Figs.2.2and2.3showdistributionsofpressure,gassaturation,temperature,andhydratesaturationafter14dayand100dayproductions,respectively.Depressurizationinducesdissociationofgashydrates,whichproducesgas,shownin

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Figs.2.2and2.3(a),(b),and(d).Also,dissociationofgashydrateisendothermicreaction,andthustemperaturedecreases(Figs.2.2and2.3(c)).

InFigure2.4,weidentifychangesinpressure,gasandhydratesaturationsatthetwodifferentmonitoringpoints(mudandsandlayers,respectively)nearthewellbore.Pressuredropsfast(Figure2.4(a)),whichcandissociategashydrate(Figure2.4(d)),andthusgasisproduced(Figure2.4(b)).Also,fromFigure2.4(c),wefindsmallverticaldisplacementawayfromthewellatthehydratezone.

However,asshowninFigure2.5,significantverticaldisplacementcanbefoundnearthewellandabovethehydratezoneafter100days,wheretheverticaldisplacementrangesupto1m,althoughtheverticaldisplacementafter14daysatthesamelocationisabout0.3m.Ontheotherhand,thesurfacesubsidencedoesnotlookcritical,havingtheverticaldisplacementof0.05mafter100daysand-0.02m(uplift)after14days.Figure2.6showsdistributionofvolumetricstrainafter100days.Weidentifysignificantcompactionnearthewellbore(particularlyjustabovetheperforationarea).

Figs.2.7-2.9showthedistributionsofeffectivestressafter100days.Thechangesofeffectivestresscorrespondtothedepressurizedarea.Specifically,thecompressivevolumetricmeaneffectivestressshowninFigure2.9induceslargecompactioninFigure2.6,followedbytheaforementionedsubstantialverticaldisplacement.

Figure2.2Distributionsofpressure(a),gassaturation(b),temperature(c),andhydratesaturation(d)after14dayproduction.

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Figure2.3Distributionsofpressure(a),gassaturation(b),temperature(c),andhydratesaturation(d)after100dayproduction.

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Figure2.4.Evolutionsofpressure(a),gassaturation(b),verticaldisplacement(c),andhydratesaturation(d)attwodifferentlocations.

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Figure2.5Distributionofverticaldisplacement.Left:14dayproduction.Right:100dayproduction.

Figure2.6Distributionofvolumetricstrain(εv)after100days.

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Figure2.7Left:Distributionofradialeffectivestress(σ’rr)after100days.Right:Distributionofchangeofradialeffectivestress(𝚫σ’rr)fromtheinitialstateafter

100days.

Figure2.8Left:Distributionofverticaleffectivestress(σ’zz)after100days.Right:Distributionofchangeofverticaleffectivestress(𝚫σ’zz)fromtheinitialstateafter

100days.

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Figure2.9Left:Distributionofvolumetricmeaneffectivestress(σ’v)after100days.Right:Distributionofchangeofvolumetricmeaneffectivestress(𝚫σ’v)from

theinitialstateafter100days.

Summary

WehavesuccessfullysimulatedthebehaviorofcoupledflowandgeomechanicsatUBGH2-6.Consideringmoreaccurateaxisymmetricformulation,weobtainedthesameconclusioninthepreviousstudythatthewellboremightnotbestable,whichcansufferfromsignificantverticalslip.Thus,carefulconsiderationofgeomechanicsbehaviorisrequired.Currently,moresimulationswithvariousproductionscenariosandfurtherin-depthanalysisareongoingtoinvestigategeomechanicalbehaviorsuchassubsidence,evolutionofeffectivestress,andanypotentialofgeologicalfailureincludingwellborecollapse.

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Task 3: Project Management, Communication, Reporting and Technology Transfer (funded by US DOE)

ThistasksupportedprojectcoordinationbetweenLBNL,NETL,KIGAM,andTAMU,andreports.

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Task 4: Gas production from a sand layer in a sand/mud layered system TimKneafsey,SharonBorglin,BinWang

Duration: 12months,i.e.,from5/16/2017to4/13/2018Budget:$70K(LBNLportion–fundedbyKIGAM)

Theessentialquestioninthistaskiscangasbeeffectivelyproducedfromthelayeredsand/mudsystem.Toinvestigatethis,layeredsand/mudsystemswereconstructedinalaboratorypressurevesselusingsimulatedmedia.Themediainthemudlayerconsistedofamixtureofsilt(200g),kaolinite(50g)diatomaceousearth(2.5g)andwater(50g),basedroughlyonmudcompositionreportedintheUlleungbasin(Kimetal,2013).Bariumsulfatewasalsoaddedtothemudlayerenhancecontrast(1g).F110sandwith30%saturationwasusedforthesandlayer.Bothlayerswerepackedinhalfcylindermoldsandfrozentoaidthepackingprocess(seeFigure4.1)inamethodsimilartheoneusedtostudymuderosionbyOyamaetal,2016.Theresultingsamplewas2inchesindiameterand6incheslong,wasplacedinaEDPMsleevewithaninnerdiameterof2inchandlength8inches.Endcapswereaddedtothesystemandthesampleassemblywasplacedinanaluminumpressurevessel.Thevesselisequippedwithtemperaturesensorsintheinletandoutletandconfiningfluidandsensorsformonitoringpressureinlet,outletandconfiningfluid.Confiningfluidconsistedofa1:1watertopropyleneglycolmixture.Thepressure,volume,andflowratesoftheconfining,upstream,anddownstreamIscosyringepumpswerealsomeasuredandrecorded.NotshowninFigure4.1isawideningoftheoutletflowtoasedimenttrapwhichwasinstalledtomonitormovementofsandandfines.

Figure4.2showsthepackedmud/sandlayeredsamplebeforeandafterpressurization.Themudlayerisontopandsandlayeronbottom.Asthefigureshows,aftertheconfiningpressurewasapplied,thesamplecompressedcausingdeformationduetothedifferentcompressibilitiesofthemudandsand.Inthistesttheoutlettubewaslocatedmidsampleandpluggedwithnylonmesh.

Methanehydratewasformedinthesampleusingtheexcessgasmethodatconstantporepressure(700psi)andconfiningpressure(820psi)at3.5°C.LiteraturesearchonconditionsintheUlleungBasinwereconductedanditwasconcludedthat100to400psiisarealisticrangeofeffectivestressrelatedtoproduction(Yunetal,2010;Kimetal,2013;Leeetal,2011).Afterhydrateformation,thesamplewassaturatedbypullingwaterthroughthesamplewithadownstreampumpatarateof0.5mL/minwhilemaintainingtheupstreampumpatconstantpressure.

Twohydrateexperimentsaredescribedbelow,oneinwhichthehydratewasdissociatedwithaslowdepressurization,theotherwithafasterpressuredecrease.Forslowdepressurization,porepressurewasreducedstepwisefrom700psito550

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psiover1.25hrs,whileinthefastdepressurizationtestporepressurewasdroppedfrom700psito500psiover10min.Intheslowdepressurizationtest,priortodissociationandafterhydrateequilibration,waterandCH4wereallowedtoflowthroughthesystemtoobserveanygeomechanicalchangesorfinesmigration.Bothtestswereconstructedsimilarly,howeverintherapiddepressurizationtesttheoutletwaslocatedmidsampleandwasscreenedwithnylonmaterial,asdepictedinFigure4.1,andnoflowofgasorwaterwasperformed.Intheslowdepressurizationtesttheoutletwaslocatedattheendofthesample,andsandmigrationwaspreventedbyanaluminumscreen(meshsize0.011inch).Inbothtestshydrateformation,dissociationandanysampledeformationwereobservedusingtheX-rayCTimaging.

(a)

(b)(c)

(d)

Figure4.1.(a)Gasproductiontestschematic.(b)schematicdiagramoftheexperimentalsetup,(c)packedmud/sandlayerinmoldspriortosamplepacking,

and(d)CTimageofpackedsampleafterpressurization.

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(a)

(b)

Figure4.2.Thepackedmud/sandlayeredsample(a)Initialcondition(b)Afterincreasingtheeffectivestressto120psi.

Slowdepressurization

ThepumpvolumevariationduringhydrateformationisplottedinFigure4.3.Duringhydrateformation53.71mL(at700psi)ofCH4wasconsumedtoformhydrate.Theconsumedgasvolumeunderthestandardconditionis2592.90mL.

Thegrayvaluevariationsinmud/sandlayersafterhydrateformationareshowninFigure4.4(a).Wefoundthatthehydratemainlyformedinthesandlayer,butitwasnotuniformlydistributed.Theincreasedgrayvalueinmudlayermayresultfromthecompactionorfromhydrateformation.Inaddition,thegrayvaluesintheinitialstate,grayvaluevariationafterhydrateandafterwatersaturationwereplottedinFigure4.4(b).

Figure4.3.Pumpvolumevariationduringhydrateformationindicatingmethaneconsumptionbyhydrateformation.

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(a)

(b)

Figure4.4.(a)comparisonofX-rayCTgrayvaluevariationinmudandsandlayers;(b)grayvaluevariationinsandlayerresultingfromhydrateformation/water

saturation.

Afterhydratewasformed,waterwasallowedtoflowintoandthroughthesampleatratesof0.5,1and2mL/minbysettingtheupstreampumptoconstantpressureandpullingwaterthroughtheoutletintothedownstreampump.Figure4.5(a)showstheCTgrayvaluevariationinthesandlayerafterthewaterflowevents.Althoughtheresultsshowsomenoise,theyaregenerallynegativeindicatingadecreaseindensityofthesample,whichmayhavebeencausedbyeitherlossoffinematerial,orlossofresidualgas.

Subsequenttothewaterflow,theupstreampumpwasfilledwithCH4whichwasallowedtoflowthroughthesampleatarateof2mL/min.ThegrayvaluevariationaftergasflowisplottedinFigure4.5(b),thegrayvaluechangedsignificantlyneartheinlet(rightside)andthevariationdecreasedalongthesample.Therewasnochangeobservedinmudlayerduetothelimitedpermeability.Inaddition,hydrateformationwasobservedduringgasflowconsumingagasvolumeof955.38mLunderstandardconditions.Figure4.5(c)showsacrosssectionfromaCTimage

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showingvariationindensityaftergasflow,showingthattheflowregionwasmuchbroaderneartheinlet(lowerpartofimage).Inbothgasandwaterflowoperations,effluentwascollectedtodetermineifanymovementoffineparticlescouldbedetected.Inbothcases,theturbidityoftheeffluentremainedunchangedindicatingnosignificantparticleproduction.

Hydratewasdissociatedbystepwisedroppingoftheporepressurefrom700psito550psiover1.25hrs(seeFigure4.6).ThecumulativeproducedgasvolumeisplottedinFigure4.7.Theproducedgasvolumewas3356.90mL(atSTP),whichwasslightlylowerthantheconsumedgasvolumeof3548.28mL,butrepresentsa95%recoveryofCH4.CH4leftinthesystem(sample,tubing,etc)couldaccountforapproximately100mL,whichwouldbringthemassbalanceto98%.

(a)

(b) (c)

Figure4.5.grayvaluevariationinsandlayerresultingfrom(a)waterand(b)gasflowing,and(c)CTimagevariationaftergasflow.

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Figure4.6.PressureprofileduringhydratedissociationandtheCTscan.

(a)

(b)

Figure4.7.Cumulativeproducedgasvolume.

Figure4.8showstheCTimagesduringthehydratedissociationprocess,inwhichthebrightercolormeansmoremasslost,indicatingthehydratedissociation.The

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hydrateinitiallydissociatedneartheoutlet(lowerpartofimage),wherefreegasexistedintheporespace.Figure4.9showsgrayvaluevariationinmud/sandlayersalongwiththesampleduringhydratedissociationprocess.Thepositivegrayvaluemeansmassloss.Asshown,hydratemainlydissociatedinthesandlayer.Butthegrayvaluedecreasedinthemudlayer,indicatingamassincrease.

Afterdissociation,waterwasflowedthroughthesample(rateof1.0mL/min)andtheresultswereshowninFigure4.10.Thetopofthefigure,4.10(a)showsthedifferenceingreyvalueafterflow.Thewatermainlyflowedthroughthesandlayer.AsshowninFigure4.10(b),somesandparticlesmovedoutneartheoutlet(leftside,darkersectionintheCTimages).Figure4.11showsthevariationinthenumberofpixelsineachsliceduringhydratedissociationprocess.Asthescannumberincreases(asshowninthelegend)dissociationisproceeding.Pixelsrepresentcrosssectionalareaofthesample,thereforresultsindicatethatthesamplebecamesmallerinthisplanewithhydratedissociation.

Figure4.8.CTimagesduringhydratedissociation.

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(a)

(b)

Figure4.9.Grayvaluevariationin(a)sandand(b)mudlayersalongwiththesampleduringhydratedissociationprocess.

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(a)

(b)

Figure4.10.(a)grayvaluevariationinlayersampleresultingfromwaterflowafterhydratedissociationinthemudlayer,sandlayer,andinthecombined(mud+sand)system.(b)CTimageoftheincreaseindensity(dissociatedsamplesubtractedfromwatersaturateddissociatedsample)variationafterwaterflow.Sandisonthebottom,mudontop.Thedarkercolorofthemudlayerindicateslittlechangein

densitywhilethebrightercolorofsandshowsagreaterchange.

Figure4.11.Variationinthenumberofpixelsineachsliceduringthehydratedissociationprocess.Thenumberofpixelsrepresentthecrosssectionalareaofthehydratesample.Ashydratewasdissociated(dissociationindicatedbyincreasing

scannumber),thesampleareadecreased.

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RapidDepressurization

ThetemperatureandpressureprofilesduringthehydrateformationprocessareplottedinFigure4.12.Porepressurewasmaintainedat700psiandthehydrateformedinabout28hbasedonthetemperaturevariation.Duetoafluidleak,noquantitativedataonamountofmethaneconsumedduringformationwaspossible.Thereasonforthepressureandtemperaturefluctuationsat~120hisduetowaterinjectionintothevessel.Aswiththeslowdepressurizationtest,thehydratewassaturatedwithwaterafterformation.ACTimageofthewater-saturatedhydrate-bearingsampleisshowninFigure4.13,showingasmalldecreaseindensityneartheoutlet.

Figure4.19summarizestheaveragegrayvaluevariationinthesandlayerduringthehydratedecompositionprocess.Theaveragegrayvaluevariationincreasedashydratedissociated,whichindicatesacontinuousmassloss.

Figure4.12.Thetemperatureandpressureprofilesduringhydrateformationprocess.Topgraphisthefirst200hrs,bottomhalfshowsthefirst40hrsinmore

detail.

29

Figure4.13.Grayvaluevariationbeforeandafterwatersaturated.Thedarkercolorinthesandlayerneartheoutletmid-samplemayindicatesomemovementofsand.

30

Figure4.14.Thetemperatureandpressureprofilesduringhydratedecompositionprocess–rapiddepressurization.Topgraphisthefirst50hrs,bottomisthesame

datashowingthefirst10hringreaterdetail.

Figure4.14showsthetemperatureandpressureprofileduringthehydratedissociationprocess.Porepressurewasdroppedrapidly(over10min)from700psito500psi,afterwhichtheporepressureandconfiningpressureweremaintainedat500psiand820psi,respectively,duringthehydratedissociationprocess.However,thetemperaturesignificantlydecreasedoncetheporepressuredecreasedfrom700psito500psi,andthenincreasedtotheinitialvalueswiththehydratedissociationduetoheattransferfromtheambient.Thetemperaturedecreasewasdueto1)endothermichydratedissociationreactionand2)Joule-Thomsoncooling.

InFigure4.15,thepressure-temperaturecurveiscomparedwiththephaseequilibriumcurveproposedbyKamath(1987).Theresultsshowthattherapiddepressurizationinducedhydratedissociationcanbemainlydividedintothreestages:1)rapidpressurerelief;2)hydratedissociationalongthephaseequilibrium

31

curvewiththesensibleheatofthereservoirsupplyingheatforthehydratedissociation;and3)thepressuredroptotheselectedgasproductionpressure,andambientheattransferdrivesthehydratedissociationreaction.

Thevolumechangeofthepressurizedmethanegas,consideredtobethecumulativegasproduction,isshowninFigure4.16.Theamountofproducedmethanegasis~82.61mLat500psi,whichcorrespondsto2892mLatSTP.Figure4.17showstheCTscannedimagesduringthehydratedissociationprocess,thebrightercolormeansmoremasslost,indicatingthehydratedissociation.Thehydratedissociationmainlyoccurredinthesandlayer.Thisgasamountislessthantheamountcollectedduringtheslowdepressurization(3357mL)butduringtheslowdepressurizationtestadditionalhydrateformationwasobservedduringmethaneflowthroughthesample.Theamountrecoveredhereissimilartotheamountconsumedduringinitialformationintheslowdepressurizationtest(2593mL).

Inaddition,theinformationintheCTimageswasextractedandillustratedinFigure4.18.Theresultsshowthatthegrayvaluevariationsinthesandlayerincreasedasthehydratedecomposed,however,thoseinthemudlayerexhibitedsimilarvalues.Theseresultssuggestthatthehydratemainlyformedinthesandlayer.

Figure4.15.Variationinporepressurewithrespecttothetemperatureduringhydratedissociationprocess,inrelationtothephaseequilibriumcurveproposedbyKamath(1987).

400

450

500

550

600

650

700

750

3 3.5 4 4.5 5

Pore

pre

ssur

e (ps

i)

Sample temperature (°C)

P-T curve

Phase Equilibrium Curve

32

Figure4.16.Volumechangeofthepressurizedmethanegasduringgasproductionprocess.

Figure4.17.Grayvaluevariationinthemudlayer(left)andsandlayer(right)alongwiththesamplelength.

33

(a)38min

(b)51min

(c)71min

(d)95min

(e)128min

34

(f)177min

(g)222min

(h)275min

Figure4.18.CTscannedimagesduringhydratedissociationprocess.Thebrightercolormeansmoremasslost,indicatingthehydratedissociationfromthelowersand

layer.

Figure4.19.Averagegrayvaluevariationinthesandlayerindicatinghydratedissociation.

35

Task5: Mechanicalandchemicalbehaviorofdiatomaceousmediumandfiltrationbehaviorofsand

SharonBorglin,BinWang,TimKneafsey

Introduction

Thistaskrequestedthatrealisticeffectivestresschangesbeappliedtosampleswithsandanddiatomaceousearth(DE)toinvestigatecompactionofDEandpossiblemovementoffines.Inaddition,claycompositioninthebasinwastobereviewedandlaboratorytestsusingrealsedimentstoinvestigatethedegreeofswellingweretobeperformed.Finally,usingrealorsimulatedmedia(sediments)themagnitudetheeffectoffinesproductionwasassessed.

AsurveyofknownliteratureonsedimentsintheUlleungbasinshowedmostlysiltandclaylayerswithanoverallmeanparticlesize~10µm,anddiatomssizesontheorderof50µm(Kimetal,2013;Yunetal,2011).Specificationontheclaytypewereuncertain,soanon-swellingclay,Kaolin,wasusedforthistask.Naturallyoccurring(realsediments)werenotavailablefortesting.Theartificiallyconstructedsedimentswereamixtureofsilt(Sigma)(200g),kaolinite(50g)diatomaceousearth(2.5g)(Sigma)andwater(50g).Imagestakenofthediatomaceousearthshowbothintactandbrokenstructures(SeeFigure5.1).

Toinvestigatemovementofdiatomaceousearthinsand,laboratorytestswereperformedbyplacingdiatomaceousmedium(mediumparticlesize50µm)indiscreteregionsofapackedsandcolumn(mediumparticlesize150µm).Abandofbariumsulfate(5µm)wasalsoplacedinthesample.Bariumsulfateisnotwatersolubleandisoftenusedasacontrastagent,anditwasusedhereasanexampleofafineparticleseasilylocatedbyX-rayCT.Theoutletofthecolumnwasscreenedtopreventmovementofsand.Thesamplewasplacedinapressurevesselandaneffectivestressof120psiwasapplied.Changesineffectivestress(120to300psi)wereappliedfollowedbyflowsofwaterandgasthroughthecolumnwithflowratesupto20ml/minandthesamplewasimagedbyperiodicCTimagingtoimagemovementofthefinerparticlesthroughthesand.Thediatomaceousearth(DE)hadalowerdensitythanthesandandthebariumsulfatehigherdensity.Despiteseverallitersofflowthroughthesystem,thebandsofDEandbariumsulfateappearedtoremainintactandnosignificantvisualmovementfinesmigrationwasdetected.Figure5.2showsthesample(flowbottomtotop)oftheoriginalsample,sampleafterwaterflow,andsampleaftergasflow.Figure5.3plotsthegreyvaluevariationsalongwiththeaxisofsediments.Greyvalueisrelatedtodensity,andchangeswouldindicatemovementofmaterial.Thegreyvalueofbariumsulfateisthebiggest,followedbyF110sand,andDEsmallest.Inthisfigure,waterflowwasfromtherighttotheleft.Asshown,thegreyvalueintheupstreamsideofBaSO4

36

layerdecreasedslightlyandincreasedonthedownstreamedge,whichmayindicatesomeminormovement.ThesamefigureshowssmallmovementofDEandsomechangesattheinletandoutlet.MoredetailedanalysisisshowninFigure5.4whichdisplayshistogramdistributionsofgreyvalueintheBaSO4layerforeachsliceupstreamanddownstreamoftheBaSO4band.ThegreyvalueofBaSO4inthecenterofthebandwasabovethelimitforthescannerassampleswithgreyvalueslargerthan3000indicateaninsufficientfluxofX-rays.Individualimagesshowdistributionofgreyvaluesbefore(red)andafter(blue)flowofwater.Thedirectionofwaterflowintheseriesoffiguresisfromtoptobottomandlefttoright,i.e.ahigherslicenumbermeansashorterdistancefromtheentrance.Slice193locatedimmediatelyupstreamoftheBaSO4layerandslice182immediatelydownstreamoftheBaSO4layer.InthisfigureiftheBaSO4finesmovedduetothewaterflow,thentheintensitydownstreamfromthebandwouldincrease,andtheintensityofthebandupstreamwoulddecrease.Thereissomeevidenceoflossofsignalinslices192-186,andsomeincreaseinsignalinslice185,butanychangeisminimal.

ThisexperimentwasrepeatedwithsimilarbandsofDEandBaSO4withthemodificationthattheBaSO4layerwasmixedtoalevelthatallowedpenetrationofx-rays.Again,inthissampleminimalifanymovementofeithermaterialthroughsandwasobservedwithaneffectivestressof120psi.Upto1400mLofwaterwaspassedthroughthesamplewithnosignificantchangestothedensityorconfigurationofthesample.

Someexperimentswereperformedwithsandsamples(F110sand,150µmmeanparticlesize)whentheoutletofthesamplewasunscreened.Figure5.5showsthesampledeformationresultingfromeffectivestresschanges(100–400psi),gasflow(upto20mL/min),andwaterflow(upto20mL/min)intheunscreenedsystem.Theresultsindicatedthatsamplescollapsedneartheoutletasaresultofsandleavingthesystem.Theflowofwaterwasmostdetrimentaltothestabilityofthesample.

InthelayeredsamplesdescribedinTask4themudlayercontainedamixtureofsilt(16µmmeanparticlesize),kaolinite(4µmmeanparticlesize),diatomaceousmedium(50µmmeanparticlesize),andbarite(4.5µmmeanparticlesize),andthesandlayerwasmadefromF110sand.Inthesesamplesmigrationofsandwaspreventedbyanaluminumscreenplacedovertheoutlet.Thisscreenhasameshsizelargerthanthemediumdiameterofsand(0.011in,280µm).Afterhydrateformed,flowsofbothwaterandmethanethroughthesamplewereappliedtoobserveanyeffecttothesampleduetomigrationofsedimentorfines.MechanicaldifferencessuchasdensitychangesandsamplesizeduetofinesmigrationwereobservedbyCT.Someincreaseindensityofthemudlayer(tophalf)due

37

compactionofthesamplewasobserved,butthiswasdifficulttoquantifyduetothepresenceofthebarite(Figure5.6).

Tofurtherassessfineparticleorsandmovement,asandtrapwasplaceddownstreamfromtheoutletduringthehydratetestsinlayeredsystems.Visualinspectionsandturbiditymeasurementsweremadeoneffluentsamplescollectedinthistrap.Turbidityvalueswerebarelyabovethebackgroundwatermeasurements,andoverallthesedimentshowednoappreciableaccumulationofmaterial.Particlesizeanalysiswasdoneonsamplesfromthemudandsandlayersfrombeforeandafterhydrateformation(seeTable5.1)whichshowedminorchangesinoverallcomposition.However,intheCTscancrosssection,somemovementofsandthroughthescreenlocatedattheoutletcanbeseen,andphysicalinspectionoftheendcapshowsthatsomesanddidmigratethroughthescreen(Figure5.7).

Conclusion

Overall,despitewaterandgasflows,hydratedissociationandeffectivestresschanges,themovementofsandandfinematerialswasnotsignificantinourexperimentalsystemsiftheoutletofthesamplewasphysicallyconstrainedbyaplugorscreen.

Table 5.1. Particle size distribution of the samples before and after hydrate formation. Changes in particle size distribution show minor changes in the fines (less than 50 um) in both the sand and the mud layer.

Size range Pre sand Post sand Pre mud Post mud

Less than 2 um 0 0 6.84% 6.08%

Between 2 and 50 um

0.78% 0.03% 59.41% 53.73%

Between 50-100 um

17.12% 18.51% 15.7% 16.79%

Between 100-250 um

74.27% 74.18% 15.9% 17.61%

Between 250 and 500 um

7.84% 7.28% 2.16% 5.76%

38

Sand

DE

Sand

Barium Sulfate

Sands

Figure5.1.Microscopicimagesofdiatomaceousearth.

Saturatedsample. After2000mLofwater

flow,20mL/minAfter1000mLofairflow,20mL/min

Figure5.2.Crosssectionofsandsamplecontainingalayerofdiatomaceousearth(DE)andbariumsulfate.Flowwasfromthebottomtothetopofthesample.

39

Figure5.3.greyvaluevariationsalongwiththewaterflowdirection

Figure5.4.BaSO4layerhistogramdistribution.Theredandbluelinesindicatebeforeandafterwaterflowrespectively.

flow

Slice 193

w Slice 182

40

(a)

(b)

(c)

Figure5.5.DeformationofF110sandasaresultof(a)increasingeffectivestress(b)gasflowand(c)waterflow.Outletwasunpluggedtoallowsandflow.

(a)(b)Figure5.6.X-rayCTimagesoflayeredmud(toplayer)andsand(bottomlayer).(a)Samplebeforehydrateformationandwater/methaneflows(b)sampleafterwater

andmethaneflows,andafterhydratedissociation.

41

Figure 5.7. Evidence for fine particles migration (end cap).

References

Barree,R.D.,&Conway,M.W.(2004,January1).BeyondBetaFactors:ACompleteModelforDarcy,Forchheimer,andTrans-ForchheimerFlowinPorousMedia.SocietyofPetroleumEngineers.doi:10.2118/89325-MS

Kamath,V.A.,G.D.Holder,DissociationHeatTransferCharacteristicsofMethaneHydrates,AIChEJ.33(1987),347-350.

Kim,H.,Cho,G.,Lee,J.,Kim,S.(2013).Geotechnicalandgeophysicalpropertiesofdeepmarinefine-grainedsedimentsrecoveredduringthesecondUlleungBasinGasHydrateexpedition,EastSea,Korea.MarineandPetroleumGeology.47.56-65.10.1016/j.marpetgeo.2013.05.009.

Lee,C.,Byun,Y.Lee,J.(2015).GeotechnicalandGeoacousticPropertiesofVolcanicSoilinUlleungIsland,EastSeaofKorea.MarineGeoresources&Geotechnology.34.150725145132000.10.1080/1064119X.2015.1070387.

Malek,K.andM.O.Coppens,Knudsenself-andFickiandiffusioninroughnanoporousmedia.JournalofChemicalPhysics,2003.119(5):2801-2811.

Oyama,H.,Abe,S.,Yoshida,T.,Sato,T.,Nagao,J.,Tenma,N.,Narita,H.(2016).Experimentalstudyofmuderosionattheinterfaceofanartificialsand-mudalternatelayer.JournalofNaturalGasScienceandEngineering.34.10.1016/j.jngse.2016.07.067.

Shi,H.,Holmes,J.A.,Durlofsky,L.J.,Aziz,K.,Diaz,L.,Alkaya,B.,Oddie,G.,(2005)"Drift-FluxModelingofTwo-PhaseFlowinWellbores."SPEJ.10(1):24-33.

Yun,T.S.,C.Lee,J.-S.Lee,J.J.Bahk,andJ.C.Santamarina(2011),Apressurecorebasedcharacterizationofhydrate-bearingsedimentsintheUlleungBasin,SeaofJapan(EastSea),J.Geophys.Res.,116,B02204,doi:10.1029/2010JB007468.

42

LBNL-KIGAMCollaborationintheInvestigationoftheGasProductionPotentialofHydrateDepositsintheKoreanEastSea

Aproposalsubmittedtothe

KoreaInstituteofGeoscienceandMineralResources(KIGAM)

and

NationalEnergyTechnologyLaboratory(NETL)

by

LawrenceBerkeleyNationalLaboratory(LBNL)

EnergyGeosciencesDivision

1CyclotronRd.

Berkeley,California94720

USA

PrincipalInvestigator:TimothyJ.Kneafsey

Co-PI:GeorgeJ.Moridis

Co-PI:MatthewT.Reagan

May27,2016

43

PROJECTDESCRIPTION

I. IntroductionThis proposal discusses two groups of tasks having the goal of improvingunderstanding of the future production ofmethane from hydrate deposits in theUlleungBasin (UB).The firstgroupof tasksarenumerical, tobeperformedusingTOUGH+HYDRATE and other codes developed at Lawrence Berkeley NationalLaboratory. The second group of tasks are experimental, to be performed inlaboratoriesatLawrenceBerkeleyNationalLaboratory.AlltasksaretobeperformedincollaborationwithorwithinputsfromKIGAM.NumericalSimulationsLawrenceBerkeleyNationalLaboratory(LBNL)isaworldleaderinhydrateresearchand the developer of the TOUGH+HYDRATE code [Moridis et al., 2008] for thesimulation of fluid and heat flow and transport in hydrate-bearing sediments.TOUGH+HYDRATE(T+H)wasdesignedtomodelnon-isothermalCH4release,phasebehavior and flow under conditions typical of CH4-hydrate deposits (i.e., in thepermafrostandindeepoceansediments)bysolvingthecoupledequationsofmassandheatbalance,andisamongthemostadvancedhydratecodesintheworld.T+His currently involved in practically every hydrate-related research project in theworld. Because of its very large computational requirements of the T+H code, aparallelversion,pT+H,[Zhangetal.,2008]hasbeendevelopedandisusedbyseveralresearchorganizations.

TheT+HcodehasbeencoupledwiththeFLAC3Dgeomechanicalcode[RutqvistandMoridis,2009; Rutqvist et al.,2009;Kim et al., 2012a] to investigate coupled flow,thermalandgeomechanicalprocessesfortheanalysisofthemechanicalstabilityoftheHBSandofthewellboreassembliesinhydratedepositsunderproduction,andtodeterminetheenvelopeofgeomechanicallysafeoperations.Morerecently,T+HwascoupledwithROCMECH[Kimetal.,2012b],apowerfulgeomechanicscodedevelopedatLBNL,whichhastheaddedbenefitofparallelization(aproblemwithFLAC3D).

A multi-year collaboration between KIGAM and LBNL has resulted in extensiveresearch into the potential for production from gas hydrates for several UBreservoirs.Tocontinuethiscollaborativework,theobjectivesofthisproposedstudyare:(a) LeveragerecentLBNLworkinthesimulationofshalegas/shaleoilsystemsto

addnon-Darcy flow, inertial effects, turbulent, andotherphysicsof flow invery high-k and low-k porous media to T+H/pT+H. This will allow more

44

realisticmodelingofthenear-wellborezoneinthethinlybeddedmud/sandsystemsfoundinUBgashydratesystems.

(b) To improve the reliability of the prediction of production behavior andwellborestabilityinUBgashydratesystems.Forthis,wewillincorporatethemostcompletegeomechanicalmodelingcapabilitiesintothecoupledpT+H-ROCMECH simulator, implement a detailed, realistic representation of thewellboreitself,andfurtherinvestigatetheeffectofhydratedissociationonthereservoirandthestabilityofthewellassembly.

(c) Via(a)-(c),createcapabilitiestobeusedinfuturecollaborativeworkbetweenKIGAMand LBNL—in the planning ofupcomingUB expeditions and in thedesignoffuturefieldtests.

(d) ToparticipateinapossibleDOE-ledcodecomparisonstudyforgeomechanicalsimulatorsandcoupledflow-geomechanical(T-H-M)codes.

TheresultsofthisworkinformsKIGAM’sProductionTechnologyStudy,whichwilldesign optimal production schemes and evaluate the safety and stability ofboreholes/wellsandthestabilityofthereservoirduringproduction.Assuchitcanhelpdeterminelocationsbestsuitedtotheupcoming3rdUBGHDrillingExpeditionandthefutureproductionfieldtest.

ExperimentalStudies

SedimentscontainingmethanehydrateintheUBhavebeendescribedtobehighplasticityclayeysiltswithaclayfractionlessthan10-20%andasandfractionlessthan10%andhavingpermeabilitiesontheorderof10-3to10-1mD,[Kwon,Leeetal.2011],organicclayofmediumtohighplasticityordiatomaceoussiltyclay[Yun,Leeetal.2011],andhigh-plasticitysiltswithspecificsurfaceSa~21to31m2/gconsistingofmicrofossilswithsomeillite,kaolinite,andchlorite.Diatomsdetermineparticlesizedistributionandcausebothadualporositymicrostructure,andhighinitialvoidratio[Leeetal.2011].Otherdescriptionsincludemethanehydratecontainedin~meter-scalethicksandlayersbetweenlayersofsedimentsasdescribedabove.

Forgasproductionfromhydrate,issuesassociatedwiththesestratigraphiesincludepermeablemudslimitingtheeffectivenessoftheseal,finesmigrationwithfluidsremoval,reductioninsedimentstrengthwithhydratedissociationandgasmigration,andthepossiblelackofgas-flowpathways.Strategiestoextractandcollectgasfromnoduleandvein-fillinghydrateconfigurationsareunderconsiderationandaddressedinthenumericalsimulations,butnoidealstrategyhasbeendeveloped.Approachingthelower-hangingfruitofproducinggasfromhydrate-bearingsandbetweenclayandsand-containingplasticsiltsisconsideredhere.

45

Hydrateproductionusingdepressurizationisconsideredherebecauseitismorelikelytohaveagreaterreachfromawellthaninhibitororthermaltechniques.Twoconfigurationsareconsidered–verticalwellsandmulti-stagehorizontalwells(Figure1).Intheverticalwellgeometry,awellisdrilledintoandfinishedinthehydrate-bearinglayer.Fluidextraction(orintroduction)isthroughthewell,andasimpleconceptualmodelofflowisradial.Fluidflowtoorfromthewellwillhavethegreatesteffectintheimmediatevicinityofthewell,thusanydamagetherefrommechanicalfailureofthemediumorwellwillaffectfutureproduction.Inthemulti-stagehorizontalwell,ahorizontalwellwouldbedrilledandfinishedwithalumberofstagesinthehydrate-bearingzone,probablytowardsthetoptotakeadvantageofgasbuoyancy.Fluidproductionthroughthefirststage(atthefarend)wouldbeperformedinitially.Ifmechanicalfailureofthewellorsedimentinthatvicinityoccurred,thatstagewouldbeshutoffandproductionfromthesecondstageimplemented.Thiswouldcontinueuntilproductionreachedstage“n”atwhichtimeanotherhorizontalmulti-stagelateralwouldbecompletedinanotherdirectionandtheprocessrepeated.Ifthehydrate-bearinglayeristhin,thismethodarrangesthewelltobeclosertoalargerquantityofthehydrateresource,andallowsformechanicalfailurewithouttotalsystemfailure.Analternativemethodforproducinggasfromalternatingmud-sandsedimentlayerswithaverticalwellistoproducegasatmultiplestagesfromdeeperlevelsoftheverticalwell.Similarlytothehorizontalwellcase,thesectionofthewellisabandonedasthereservoirisdepletedandthesedimentssubside.Toavoidshearingofthecasing,productionschedulesfrommultiplewellsneedtobecoordinatedcarefully,withmonitoringofthereservoircompactionandseafloorsubsidence.Thistypeofreservoirmanagementhasbeenproposedandimplementedinoilfieldswithshalelayerswhichcauseswellshearfailureduetoslipatsedimentaryboundariesinducedbysubsidence.Systemoptimizationwouldberequiredincludingunderstandingofthegeometries,mechanicalandhydrologicalcharacteristicsofthedeposit,andeconomicsofoperation.

46

Figure1.(Left)multi-stageverticalwellgeometry,(Right)multi-stagehorizontal

wellgeometry,(Bottom)Multi-stagewelleliminatingendstage.

Regardlessofthewellgeometry,anumberofissuesneedtobeaddressed:mechanicalandhydrologicalbehaviorofthereservoirmaterialsunderproducingconditions.

II. ProjectTasksTheproposedprojectisacontinuationofongoingLBNL-KIGAMcollaborativestudiesonthesubjectofgasproductionfromhydrates.Intheensuingdiscussion,referencesto“effort”aretoindicatethetimeneededbyLBNLscientiststoaccomplishthetasksdescribedlaterinthissection.NumericalsimulationstudiesaredescribedinTasks1-3, and Laboratory studies are described in Tasks 4 and 5. Regarding some of thegeomechanicalnumericalsimulationworkinTask2,LBNLwillcoordinatewiththeresearchteamofDr.KimatTexasA&MUniversityforbettercouplingalgorithmfornumerical stability and accuracy, and LBNL will also share and discuss thegeomechanicalsimulationresultswithDr.Kim,asrequired.NumericalSimulationTasksTask1: Enhanced flow simulation capabilities for the simulation of complex

mud/silt/sandhydrate-bearingsystemsSubtask1.1:Non-DarcycapabilitiesforT+HcodesDuration: 6months,i.e.,from10/1/2016to3/31/2017Budget:$25K(LBNLportion-fundedbyUSDOE)

47

Previousstudieshavedemonstratedthetechnicalfeasibilityofgasproductionfromhydrate deposits in general, and the feasibility of production from the reservoirsidentifiedintheUBGH1andUBGH2drillingexpeditions.Thesystemsmodeledtodateinvolved sandy production zones layered betweenmud/silt barriers, and have berepresentedbytraditionalDarcy’sLawtreatmentofflowinporousmedia.Currentwork at KIGAM involves review of UBGH1 and UBGH2 data (sedimentology andgeochemical analysis, geophysical inversion and seismicmodeling) and geologicalmodeldevelopmenttobetterunderstandandcharacterizethesereservoirs.Tomodelsuchdepositsmay requiremoreadvancedsimulation capabilities that include thecomplex behavior of low effective permeability fracturedmud/clay systems, low-permeability/high-saturation hydrate inclusions, and transport through high-permeability pathways.We propose to expand the capabilities of the T+H/pT+Hcodesthroughtheadditionalofseveralnon-Darcyfloweffects:(1) Implementation of non-Darcy flow effects for high-permeability media

(fracturedhydrates,verticalpathwaysinfracturedmuds/silts),including:(a) The Drift-Flux model [Shi et al., 2005; Livescu et al., 2010] to allow the

simulationoffluidflowandaccuratephasesegregationinhigh-permeabilitypathways,i.e.,wellboreflowandflowinpathwayscreatedbydissociationofhydrates.

(b) Forchheimer flow; for the representation of high-velocity turbulent flowthroughhigh-kmedia,particularlyinhydrate-freeregionsnearthewellbore.

(2) Implementation of non-Darcy flow effects for very low-k media (muds, highhydratesaturation,otherlow-effectivepermeability),including:(a) Knudsendiffusion;forsystemswherethegasmean-freepathiscomparable

totheporediameter.(b) Klinkenberg effects; to correctly represent gas flow in low-

permeability/tightmedia.Theinclusionofsuchinertialeffectsisdeemedimportantbecausetheeffectivepermeabilitiesofhydrate-bearingmedia(HBM)areoftenatalevelcomparabletothatofultra-tightmedia(suchasshalegasreservoirs),andbecausetheyareapossibleexplanationofthehigherthanexpectedpermeabilitiesobservedinHBMunderproduction.

Notethat,althoughthedurationofthisprojectisshortandthebudgetislimited,thenewsimulationcapabilitieswillleveragerecentNETL-fundedworkoncoupledT-H-Msimulationofshalegasandshaleoilsystems.Thecapabilitiesneededtorepresentmud/clay systems are similar to those currently implemented in theTOUGH+RealGasBrine and TOUGH+MultiComponentMultiphase simulators, andthesefeatureswillbeadaptedtoT+H/pT+H.Subtask1.2:Simulationofcomplexmud/silt/sanddepositsDuration: 6months,i.e.,from12/1/2016to6/30/2017Budget:$25K(LBNLportion-fundedbyUSDOE)

48

UsingthecapabilitiesdevelopedinSubtask1.1andgeologicalmodelsdevelopedincollaborationwithKIGAM, this subtaskwill evaluate via numerical simulation theproduction behavior the mud/silt/sand discovered in the previous UBGH1 & 2expeditions. Given the limited budget and duration, a limited set of “schematic”systemswillbeexaminedtodeterminetheeffectoftheadditionalmodeledprocesseslistedinSubtask1.1,andtodeterminethepotentialproductivityofsuchsystems.Iftheseresultsprovetobepromising,futurecollaborativeworkmaybeproposedtofurtherevaluatetheimportanceoftheseeffects.This taskwill also leverage the resultsof the laboratorywork proposed by otherKIGAMcollaborators(Kneafsey,Seol)andincorporateanynewinformationgainedabout effective permeability and flow through sand/mud/silt systems. Suchlaboratory data, if suitable, will be incorporated as options (describing newrelationshipsbetweenkeffandSHformud/siltsystems)intotheT+Hcodeandwillbeusedtovalidateavailableflowmodelsandre-analyzetheresultsofearliertests.Task2: Enhancedgeomechanicalcapabilitiesforthepredictivesimulationof

potentialUBGHfieldtestsitesDuration: 6months,i.e.,from5/16/2017to11/31/2017Budget:$80K(fundedbyKIGAM)Recent collaborative studies between KIGAM and LBNL have demonstrated theimportanceofconsideringgeomechanicsduringproductionfromgashydrates,andhowgeomechanicalstabilitylimitationsmay inhibitproduction fromanotherwisepromisinghydratedeposit.Themost recentUBGH2simulations,performed in3Dwithcoupledgeomechanics(usingT+H-ROCMECH) indicatethatsubsidenceof theoverburdenandpotentialupliftoftheunderburdenmayjeopardizewellborestabilityforsystemswithcertaingeomechanicalproperties.DiscussionswithKIGAMindicatethatwellborestability isofparticularconcern infield-testdesign.Inthistask,weproposedtoimplementarealisticrepresentationofthewellboretobetterunderstandthehazardscreatedduringproduction fromUBreservoirs.ThesimulationsinthistaskaretobeconductedusingT+HcoupledtotheROCMECHcode(Kimetal.,2012).Inaddition,thistaskwillleverageotherresearchbeing conducted at LBNL and we will consider the use of new, more advancedgeomechanicalsimulatorsthatarecurrentlyunderdevelopmentifsuchmethodsaredeemedmoresuitabletosolvingthisproblem.Withthefull-wellboretreatmentinplacefortheUBGH2-6case,wewillassesswellstability and the possibility of cement failure during production for variousproductionscenariosusing3Dparallelcoupledflow-geomechanicalsimulation.Wewillalsore-evaluatethegeomechanicalstabilityoftheformationandtheproductivityofthereservoirbyconsideringplasticityandlarge-deformationgeomechanics.ThisworkwillalsoincludeanefforttovalidatecoupledTOUGH+ROCMECHvs.thepre-existingexperimentaldata.

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Becauseoftheverydemandingcomputationalrequirementsofthiswork,itwillnotbe possible to analyze the geomechanical behavior ofmore than one deposit. Toleverage previous work, we propose to limit the simulations to the UBGH2-6reference case developed during the previous round of LBNL-KIGAM collaboratorstudies.Task3: Project Management, Communication, Reporting and Technology

TransferDuration: 20months,i.e.,from10/1/2016to5/30/2018Budget:$5K(LBNLportion–fundedbyUSDOE)As in any collaborative project, significant communications and interactions arenecessary between LBNL and KIGAM. These include telephone discussions,telephone- and video-conferencing, e-mail communications, in addition to reviewmeetings(attheLBNLcampusand,possibly,attheKIGAMheadquartersinKorea)forjointstudiesandforprojectprogressreview.Reportingrequirementsinclude(a)theLBNLsubmissionofquarterlyprogressreportstotheKIGAMteambye-mailand(b)afinalprojectreportby6/1/2017,inadditionto(c)notificationswhensignificantmilestonesarereached.Technologytransferincludesthepublicationofpapersandscientific presentations at professional meetings. Technology transfer may alsoincludetrainingofKIGAMscientistsintheuseoftheenhancedLBNLT-H-Mcodes(possiblyconductedatLBNLfacilitiesinBerkeley,afteracommensurateincreaseintheprojectbudget).LaboratoryStudyTasksTask4: Gasproductionfromasandlayerinasand/mudlayeredsystem

Duration: 12months,i.e.,from5/16/2017to4/13/2018Budget:$70K(LBNLportion–fundedbyKIGAM)

Theessentialquestionis:Cangasbeeffectivelyproducedfromthelayeredsand/mudsystem?

Proposedstudy:

Alayeredsand/mudsystemwillbeconstructedinalaboratorypressurevesselusingreal(fromKorea)orsimulatedmedia.Itisenvisionedthata2-layersystembeinitiallyinvestigatedbecausethatcontainstheessenceoftheproblem.Oneofthelayerswillbecomposedofsiltsanddiatoms,theotherofsandalsocontainingsomesiltsanddiatoms(Figure2).Methanehydratewillbeformedinthesample(primarilyinthesandusingtheexcessgasmethod),andthesamplewillthenbe

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saturatedwithwater.Uponwatersaturation,thesamplewillbeflowedinitiallyunderconditionswheregashydrateisstable,examininganyfinesmigrationusingX-rayCTandpossiblyanopticalmethodintheflowingfluid.Aftereitherequilibrationorasufficienttime,thesystemwillbe1.slowly,or2.rapidlydepressurizedtomimica1.smalleror2.largerchangeineffectivestressrepresentingdistancefromthewell.Theexcessstresswillbecarefullycontrolledandthefluids,solids,andgasproductionwillbeobservedusingavarietyoftechniques.

Figure2.Gasproductiontestschematic.

Followingeachtest,bothsandandmudfractionswillbecarefullysampledforfurtheranalysisbyKIGAMworkingwiththeUSGStoevaluatethetransportoffinesinbothmedia.

Task5: Mechanicalandchemicalbehaviorofdiatomaceousmediumandfiltrationbehaviorofsand

Duration: 12months,i.e.,from10/1/2016to8/30/2017Budget:$70K(LBNLportion–fundedbyUSDOE)

Mechanicalbehavior:Theliteraturecitedhereindicatesthatthediatomaceousnatureofthemediummustbeconsidered,asthediatomsarelikelytobreakunderreasonablestress[Kwonetal.2011,Leeetal.2011,Yunetal.2011]causingcompaction,andproductionofsmallerfinesthatmaybetransported.

Chemicalbehavior:TheeffectoffresheningwasbroughtupbyKwonetal.[2011].Althoughitwasnotpossibletodifferentiatetheeffectofmediumalterationbygasgenerationandfreshening,thiswasusedtopartiallyexplainhighercompressionindicesuponhydratedissociation.

Filtration:Apumpedwellwilldrawfluidthroughthesand,andthatfluidmaycarryfines.Productionofgasinthehydratemaystirupthemedium(typicallysand)

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whichisunderloweffectivestress,orgasbubblesmaymechanicallyscrubparticlesfromsandgrains,allowingthemtobetransported.

Proposedstudy:

a. UsingnumericalsimulationofrealisticUBconditionseitherfromtheliteratureorfromKIGAM,asetofrealisticeffectivestresschangesrelatedtoproductionwillbedetermined.Thesewillbecomparedtotheliteraturefordiatomaceousporousmediumbehaviortoestimatetheextentofthisissue.Notethatforeitherwellgeometry,conditionsnearthewellarecritical.Forahorizontalwellinsand,thechangeineffectivestressonthediatomaceousmediumwillbemitigatedbythepresenceofthesandlayer.Laboratorytestswillbeperformedtoexaminecompactionofreal(suppliedbyKorea)orsimulateddiatomaceousporousmedia,andtheproductionandtransportofcreatedfines.Asdiatomaceousearthisafiltermaterial,transportmaynotbeanissue,howeverthistransportduringconsolidationparticularlywherepossiblediatombreakagecouldoccurhasnotbeeninvestigated.

b. Thecompositionofclaysintheanalysesrevieweddoesnotindicateastrongswellingfraction.Theinitialpartofthestudywillinvolvereviewingclaycompositionfromliteratureandreportsanddeterminingthemagnitudeofpotentialswelling.Laboratorytestsusingrealpreservedsedimentsaredesiredtoexaminethemagnitudeoftheswellingeffect.Inthesetests,themediumwillbeappropriatelycompactedintoinanoedometric(~zero-lateralstrain)cell,andsaturatedwithwaterhavingadesiredsalinity(e.g.seawater).Thesamplewillbeloadedcompressively,andthenfreshwatersuppliedwhilemonitoringswelling.

c. UsingrealisticconditionsfromnumericalmodelingorsuppliedfromKIGAM,thepotentialforfinesmigrationwillbeconsidered.Usingreal(suppliedbyKorea)orsimulatedmedia,themagnitudeofthisproblemandhowitcouldaffectgasproductionfromhydratewillbeinvestigatedusingsimplifiedsetups.

V. DeliverablesThedeliverablesofthisprojectinclude:

(1) AminimumofonepaperonthetopicofT-H-MmodelingofproductionandwellborestabilityinUBgashydratereservoirs,submittedforpublicationinapeer-reviewedjournal.

(2) Samplesfromtestsperformedforanalysis(e.g.Task4)byKIGAM.

(3) AreportonthenumericalsimulationstoKIGAMby10/31/2017.(4) Shortmid-termprogressreporttoKIGAMby10/31/17.(5) Finalreportincludingall5tasksbyMay30,2018.

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VI. ProjectLocation,DurationandBudgetTheprojectwilllastfromOctober1,2016toMay30,2018.MostoftheworkwillbeconductedattheLBNLcampusinBerkeley,California.Thetotalrequestedbudgetfortheprojectis$275K.Ofthe$275K,$150KwillbeprovidedbyKIGAM;theremaining$125KwillbeprovidedbytheU.S.DepartmentofEnergy(DOE)astheircontributiontotheU.S.-Koreacollaborativestudiesongasproductionfromhydrates.TheKIGAM-fundedportionincludes$30KfundingwithinTask2forDr.KimatTexasA&MUniversity.Theeffortrequirementsdescribedinthisproposalcorrespondtotheentireproject,andnotonlytothepartfundedbyKIGAM.

References:Kim,J.,Moridis,G.J.,Yang,D.,Rutqvist,J.(2012a).“NumericalStudiesonTwo-WayCoupledFluidFlowandGeomechanicsinHydrateDeposits.”SPEJ.June2012,485-501.

Kim,J.,Moridis,G.J.,Rutqvist,J.(2012b).“CoupledflowandgeomechanicalanalysisforgasproductioninthePrudhoeBayUnitL-106wellUnitCgashydratedepositinAlaska.”J.Pet.Sci.Eng.92-93,143-157.

Kwon,T.-H.,K.-R.Lee,G.-C.ChoandJ.Y.Lee(2011)."GeotechnicalpropertiesofdeepoceanicsedimentsrecoveredfromthehydrateoccurrenceregionsintheUlleungBasin,EastSea,offshoreKorea."MarineandPetroleumGeology28(10):1870-1883.

Lee,C.,T.S.Yun,J.-S.Lee,J.J.BahkandJ.C.Santamarina(2011)."GeotechnicalcharacterizationofmarinesedimentsintheUlleungBasin,EastSea."EngineeringGeology117(1–2):151-158.

Livescu,S.,Durlofsky,L.J.,Aziz,K.,Ginestra,J.C.(2010)."Afullycoupledthermalmultiphasewellboreflowmodelforuseinreservoirsimulation."J.Pet.Sci.Eng.71:138-146.

Moridis,G.J.,Kowalsky,M.B.,Pruess,K.,(2008)."TOUGHþHYDRATEv1.0User’sManual:ACodefortheSimulationofSystemBehaviorinHydrate-BearingGeologicMedia."ReportLBNL-00149E,LawrenceBerkeleyNationalLaboratory,Berkeley,CA.

RutqvistJ.,MoridisG.J.(2009)."NumericalStudiesontheGeomechanicalStabilityofHydrate-BearingSediments."SPEJ.14:267-282.SPE-126129.(2009).

Rutqvist,J.,Moridis,G.J.,Grover,T.,Collett,T.(2009)."Geomechanicalresponseofpermafrost-associatedhydratedepositstodepressurization-inducedgasproduction."J.PEt.Sci.Eng.67:1-12.

Shi,H.,Holmes,J.A.,Durlofsky,L.J.,Aziz,K.,Diaz,L.,Alkaya,B.,Oddie,G.,(2005)"Drift-FluxModelingofTwo-PhaseFlowinWellbores."SPEJ.10(1):24-33.

Yun,T.S.,C.Lee,J.-S.Lee,J.J.BahkandJ.C.Santamarina(2011)."Apressurecorebasedcharacterizationofhydrate-bearingsedimentsintheUlleungBasin,SeaofJapan(EastSea)."JournalofGeophysicalResearch:SolidEarth116(B2):n/a-n/a.

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Zhang,K.,Moridis,G.J.(2008)."Adomaindecompositionapproachforlarge-scalesimulationsofcoupledprocessesinhydrate-bearinggeologicmedia."Proc.6thInternationalConferenceonGasHydrates,July6–10.Vancouver,BritishColumbia,Canada.

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