EPAWorkshoponHydraulicFracturing,WorkshopNo.1,ChemicalsFractureFluidAdditiveandFormationDegradationsGeorgeE.KingApacheCorporationFractureAdditiveandFormationddReactionsanDegraationsSubsurfaceReactiveTargetsChemical&PhysicalReactionControlsReactiveTargets•Rock(shale,sandstone,limestone,etc.)–MatrixReactionControls•Access(inhibitioncontrols)–Permeability(canreactantsreacheachother?)–NaturalFractures–HydraulicFractures–Fluids(nonHCgases,waters,–Area‐to‐volumeratio(howmuchdiffusioncanoccur?)–Inhibition– (diffusion,viscosity,coatings,form,etc.)hydrocarbons)•Tubulars(variousalloys)•Cement•Reactionvariables–FlowRateandPressure–Temperature–Pressure•Drillingcomponents•FractureAdditives–Time(averagefrac3hrsatpressure,2to4weekscleanup)–Volumes–By‐productsolubility–Re‐precipitationWellDescribedShale/ dReactionDegraationChemicalPhysical•IonTransfer,CEC•Solutionandre‐precipitationPhysical•Creep(Deenadayalu,2010)•OsmoticSolutionandreprecipitationRxw/proppant.Osmotic•Dispersion(breakage)•Saltimbalancedisaggregation(drilling)–Resolvedbymorecloselymatchingsalinity.ShalePorosityvs.PermeabilityPermeabilityProppantDiagenesisSPE131782,LaFollette andCarman•Proppants–theconductivityofproppedProppantsconductivityaproppedfracturecandecomposeinsomeconditions.–ProppantdecompositionfluidreactionProppantdecompositionfromprop‐reaction–Propembedmentintotheformationgougesout/liberatessmallformationparticlesformationparticles.ChangesinRecoveredWaterh ll dComposition:Sae+Prop+FuiZeolitesarethemostcommonprecipitatedmineralwhenshalesandproppantareheatedwithsaltwater.ZeolitesCZ litInordertobeazeolite,theratio(Si+Al)/Omustequal1⁄2andtypicallyhavelargevacant,interconnectedspacesintheirstructurethatformlong,widechannelsofvaryingsizes.CommonZeolitesy gThefirstzeolite formedisoftenalteredtoanotherspecies.SPE139875ManyFormationDegradationsDirectlyTiedtoHLdMi lA idp–owpHCreatebyCO2orneracReductionofConductivitywithStressConductivityDecompositionReactionsofMost‐dd(f)CommonFracAitives1o3•Proppant–Physical•Embedment(pushesupparticlesfractureface)Embedment(pushesparticlesoffracture•Erosive– minoreffectwithmaximumimpactonperforationsinthecasing(largeparticles,roughsurfacesandhighvelocities)–Chemical•Diagenesis–solutionandcommonre‐precipitationofsilicaandsomealuminumoxides.Strengthloss=20%.DecompositionReactionsofMost‐dd(f)CommonFracAitives2o3•FrictionReducer–Physical– lowersfrictioninpipeby25to35+%(decreaseshorsepower&resultantemissions)ChemicalhighMWpolyacrylamideabsorbsinrock–Chemical–polyacrylamideabsorbs•Surfactants– (flow‐back,dispersion,IFT,etc)–mostadsorbandarelost.•Gellants– guar,cellulosederivatives,etc.–Physical– increasesviscosity&proppantcarryingabilitydecreasesleakoffabsorbsformationability,decreasesleakoff,absorbsinformation–Chemical– breakers&temperatureinduceddegradationleavespartlybrokenpolymerinpores.DecompositionReactionsofMost‐dd(f)CommonFracAitives3o3•GelBreakr–ammnimpersulfate–reducese sousu ategelviscosityinlowertemperatureformations.Thematerialsremainwithfluids.•Biocides–oxidizingbiocidevs.metabolictoxin?Besthavelowbioaccumulationandbio‐d d tiUViidegradation.Someusenclearflus.•ScaleInhibitors– phosphonates,phosphateestersPolymerssorptionlossesno,Polymers–sorption,degradationofphosphonate orphosphates.Polymerbreakdowniscommondegradation.ObservationsConventionalRockssandstone&carbonatesUnconventionalRocksshalesmudstonessiltstonesetcsandstone&carbonates•ReactionsarewelldescribedinLiterature– 60+yearsofdatashales,mudstones,siltstones,etc.•ReactionsonlystartingtobedescribedinLiterature•Accessismajorlimiter‐allRx•Adsorption,absorption&gradedreleaseverycommon.•Access– the0.1to5000+mDAccessismajorlimiterallRx–Shaleperm100to500nano‐Darcies(0.0001to0.0005mD)limitsrateoffluidmovementtomillimeters/yr.–Shaleporesizeof0.3micronbarsperm&Area‐to‐Volumeratiosof20,000to30,000aremajorchemical&physicalreactiont lpwaterentryintothematrix.–Area‐to‐volumeratiosreducedintothe100to1000:1range,notthe30,000+:1ofamatrixreactionorthe100 000:1rangeofgroundupshalecontrols•Meaningfulworkdoneoncoreandappearsreflectiveofwhathappensintherock100,000:1rangeofgroundupshaleparticles.–Reactionstudiesinvolvingground‐upshalearehighlysuspectandaworst‐possible(unachievable?)case.happensintherock.p( )Support(fortherecord)Slidesrecord)•ShaleCharacteristics•ReferencesMolecularDiameterFreeman,SPE141125pH5FluidEffectonHaynesvilleShaleHaynesvillepHatVariousintheFlowBackVariousPointsProppantDiagenesisConclusionsfromSPE139875ChangesinRecoveredWaterl dComposition:Prop+FuiTestTestofOnsetofProppantDiagenesis–requiresformationpresentformationtobepresent.Diagenetic materialsformedonalltypesofproppant– sand,ceramic,glass,resincoatedmaterials,steelballs,etc.SameTestwithAnotherShaleShaleReactivity•Shalesreactivefollowingmanners:reactiveinthefollowingmanners:–ChemicalReactivity•Shaleunitsarelaminatedandcontainacidhighlylaminatedcontainsolubleminerals•Acidsolublemineralsarehomogenizedintheshalebulkmatrixandnaturalfractures•Reactivefluidsmaybecapableofetchingthefaceofshalefractures.•Aluminumoxide,Al2O3WaterChemistryChanges•Waterchemistryinthepresenceofshalechemistrypresence(Haynesville)changedoutto240days–Ca++Si+/‐Cl‐HCO‐increasessharplyandthen–Ca,Si/,Cl,HCO3increasessharplyandthendecreased=>dissolutionfollowedbyprecipitation–Theformationinitiallyweakensthenstrengthensformationinitiallyweakens,strengthens.–Thereisabouta10%to20%netstrengthloss,butthatchangesmoisturelevelsmaybeduetochangesinmoistureoradjustmentofmineralstructurestosalinitychange.Additive&FormationDegradationConclusions•SeveralchemicalandphysicalactionsoccuringSeveralchemicalphysicalactionsoccuringovertime•Shortmisleadingtimetestsmaybemisleading–Re‐precipitationandProp/Shalestrengtheningobserved–Additivesoftendisappeartoabsorption,adsorptionprecipitationormodification,precipitationmodification–“Lost”additivesmayormaynotcomebackasextremelydilutesolutions.ProppantChangesAfter120daysofexposure,allthesilicaintheproppanthadbeenleachedout,leavingaluminumoxidebehind.Precipitationofmineralsontheproppantgrainswasvaried.VariablesthatInfluenceRockTypingInfluence1. Porosity2TOC.3. Quartz4. Calcite5. Dolomite6. Illite7. MixedClay8. Siderite9Totalfeldspar.10. TotalCarbonate11. TotalClayContentThefirstthreeprincipalcomponentsexplainalmost70%ofthevariationinthedataset.InteractionsofComponentsExposuretoFlowbackWaterLaFollette,SPE140110TDS=158,000w/barium,strontium,sodiumandcalcium.pH=5.8.PetrofaciesVariationShales‐Composition•SedimentaryinNature–Sealandgumboshaleshighclaycontent– 40%+claysOrganiccontentto30+%,Organiccontentof10–Gasproductiveshales– calledashalebecauseofparticleActuallysiltstonemudstone.particlesize.Actuallyasiltstoneormudstone.<10to30%clayandTOCusually1%to8%.–Young’smodulusofasrosectiveshalesplotsgp pwithtightgassands– distinctlydifferentfromsealandgumboshales(Britt,2009)CoreChemistryMineralogy/MineralogyReferences•Al‐Bazali,T.M.,et.al.:“AnexperimentalInvestigationontheImpactofCapillaryPressure,DiffusionOsmosis,andChemicalOsmosisontheStabilityandReservoirHydrocarbonCapacityofShales,”SPE121451paperandpresentation,SPEOffshoreEuropeOilandGasConferenceandExhibition,Aberdeen,UK,8‐11September2009.•Beihoffer,T.W.,Dorrough,D.S.,Schmidt,D.D.:“TheSeparationofElectrolyteEffectsfromRheologicalEffectsinStudiesofInhibitionofShaleswithNaturalMoistureContent,”SPE18032,63rdAnnualConferenceandTechnicalExhibition,Houston,2‐5October1988.•Britt,L.K.,Shoeffler,J.:“TheGeomechanicsofaShalePlay:WhatmakesaShaleProspective!”SPE125525,Presentedat2009SPEEasternRegionalMeeting,Charleston,WV,USA,23‐25September2009.•Dacy,J.M.:“CoreTestsforRelativePermeabilityofUnconventionalGasReservoirs,”SPE135427paperandpresentation,SPEAnnualTechnicalConferenceandExhibition,Florence,Italy,19‐22September2010.•Deenadayalu,C.,Suarez‐Rivera,R.:“TheEffectofHorizontalCompletionsontheBreakdownPressuresofAnisotropicGasShale,”ARMA10‐477,SaltLakeCityUtah,27‐30June2010.•Duenckel,R.,et.Al.:“ProppantDiagenesis– IntegratedAnalysisProvideNewInsightsintoOrigin,Occurrence,andImplicationsforProppantPerformance,”SPE139875paperandpresentation,SPEHydraulicFracturingTechnologyConferenceandExhibition,TheWoodlands,TX,USA,24‐26•Freeman,C.M.:ANumericalStudyofMicroscaleFlowBehaviorinShaleReservoirSystems,”SPEandpresentation,SPEAnnualTechnicalConferenceandFreeman,NumericalMicroscaleBehaviorTightGasandGasReservoirSystems,141125paperpresentation,TechnicalConferenExhibition,Florence,Italy,19‐22September2010.•Grieser,B.,Wheaton,B.,Magness,B.,Blauch,M.,Loghry,R.:“SurfaceReactiveFluid’sEffectonShale,”SPE106815,2007SPEProductionandOperationsSymposium,OklahomaCity,OK,USA,31March– 3April2007.•Kale,S.,Rai,C.S.,Sondergeld,C.H.:“RockTypinginGasShales,”SPE134539paperandpresentation,SPEAnnualTechnicalConferenceandExhibition,Florence,Italy,19‐22September2010.•King,G.E.:“ThirtyYearsofGasShaleFracturing:WhatHaveWeLearned?,SPE133456paperandpresentation,SPEAnnualTechnicalConferenceandExhibition,Florence,Italy,19‐22September2010.•King,G.E.,Lee,R.M.:“AdsorptionandChlorinationofMutualSolventsUsedinAcidizing,”SPE14432,SPEProductionEngineering,May1988,p205‐•LaFolletteRFP:“ProppantDiagenesis:Results”SPEpresentationUnconventionalerencePittsburgh‐25FebruaryLaFollette,..,Carman,.S.ProppantDiagenesis:ResultsSoFar,131782presentationandPaper,SPEUnconventionalGasConf,Pittsburgh,PA,23February2010.•LaFollette,R.F.,Carman,P.S.:“LongTermStabilityofProppantsExposedtoHarshShaleReservoirConditions,”SPE140110paperandpresentation,SPEHydraulicFracturingTechnologyConferenceandExhibition,TheWoodlands,TX,USA,24‐26•Milner,M.,Petriello,J.,McLin,R.,Gathogo,P:“ImagingTextureandPorosityinMudstoneandShale:FindingsfromPetrographic,Secondary,andIon‐MilledBackscatter,SEMMethods,”4thB.C.UnconventionalGasTechnicalForum,April2010.•Muniz,E.S.,da Fontoura,S.A.B.,Lomba,R.F.T.:“DevelopmentofEquipmentandTestingMethodilogy toEvaluateRock‐DrillingFluidInteraction,”ARMA/NARMS04‐599,20046thNorthAmericaRockMechanicsSymposium,Houston,TX,5‐9June2004.•Muniz,E.S.,da Fontoura,S.A.B.,Durate,R.G.,Lomba,R.F.T.:“EvaluationoftheShale‐DrillingInteractionforStudiesofWellboreStability,”ARMA/USRMS05‐816,AlaskanRocks2005,Anchorage,Alaska,25‐29June2005.•SarwarMU:“GelDegradationStudiesOxidativeBreakersOptimizeBreakerConcentrationEffectiveeakProfilesatLowandMediumTemperature,..DegradationStudiesofOxidativeandEnzymeBreakerstoOptimizeBreakerTypeandConcentrationforEffectiveBrProfilesTemperatureRanges,”SPE140520paperandpresentation,SPEHydraulicFracturingTechnologyConferenceandExhibition,TheWoodlands,TX, USA,24‐26January2011.•Tutuncu,A.N.:“Anisotrophy,CompactionandDispersionCharacteristicsofReservoirandSealShales,”ARMA10‐344,SaltLakeCityCity,UT,27‐30June2010.•VanOort,E.,Hale,A.H.,Mody,F.K.:“ManipulationofCoupledOsmoticFlowsforStabilizationofShalesExposedtoWater‐BasedFluids,” SPE20499.AnnualTechnicalConferenceandExhibition,22‐25October1995.