Slickwater-Fracturing

ThefollowingispresentationisbasedprimarilyoninformationcontainedinSPE115766SlickwaterFracturing–FoodforThoughtT.T.Palisch,CARBOCeramics,Inc.M.C.Vincent,InsightConsultingP.J.Handren,DenburyResourcesApril8,2009SPEArkansasSection,Ft.Smith,AROutline•SlickwaterFracturing–“FoodforThought”–Introduction/Definitions–FracGeometry/Complexity/Width–ProppantSettling,Transport&Deposition–ConductivityRequirements&Proppants•ClosingThoughtsDefinitions•Slickwaterfrac,Waterfrac,Riverfrac–“Slickened”toreducefrictionintubing/casing•FrictionReducerand/orLinearGel–Lowviscosity,highpumprate–Lowproppantconcentrations,butstilllargeproppantvolumes•TheseareNOTproppantlesswaterfracs•“Hybrids”–Typicallyuseacombinationofcross-linkedstagesandslickwaterpad/sweepsSlickwaterFracPros&Cons•Benefits–Potentialforreducedgeldamage•SomeconcernbreakingPAfrictionreducers–Typicallylessexpensive–Typicallyresultinmorecomplexfracturing–“Disposal”and/orreuseofproduced/loadwater•Concerns–ProppantTransport•bothfraclengthandverticalcoverage–Water•bothsupplyandformationsensitivity–FractureWidthFracWidthXLGelvsSlickwaterXLFluids“Moderate/low”conc.XLFluidsHighconcentrationSlickwaterFluidsVeryLowconcentrationGelFiltercakeweffIsitpossiblethatourslickwaterproppedwidthisactuallywiderthanourcurrentXLgelfracs?0.00000.05000.10000.15000.20000.25000.30000204060801001201402%KCL,Xf=1000'2%KCL,Xf=300'PumpRate,BPMEffectiveWidth,inchesEffectiveWidths-SlickwatervsXLGelledWater*Doesnotincludeanyproppanteffectsonviscosity*Assumes:E=6E6psiH=100'WaterfracFluidsEffectiveProppedWidth-30#XL,8PPA,40BPMEffectiveProppedWidth-25#XL,6PPA,50BPMEffectiveFracWidthComparisonFractureComplexityDoFracsresembleourmodels?-500050010001500200025003000-50005001000150020002500Easting(ft)Northing(ft)ObservationWell1ObservationWell2Perforations-1000-500050010001500200025003000-1000-50005001000150020002500West-East(ft)South-North(ft)ObservationWell1ObservationWell2PerforationsSlickwaterFracXLGelfracFracComplexitySPE95568…iscurrentlydifficultatbest…iscriticalforoptimization-3000-2500-2000-1500-1000-500050010001500-1000-500050010001500200025003000West-East(ft)South-North(ft)FractureStructuresObservationWellModelingSlickwaterFracs….SPE90051Microseismicmappinghelpsusunderstandwherethefracfluidwent.…Butwhereistheproppant?Stokes’Law•PredictsSingleParticleSettlingRate•Asμdecreases,settlingvelocityincreases.•Ifρpρf,thentheproppantsettles•Asproppantdpgetslarger,settlingincreasesexponentially.Vsistheparticlesettlingvelocity,ρpisthedensityoftheparticles,ρfisthedensityofthefluid,gistheaccelerationofgravity,μisthefluidviscosity,anddpisthediameteroftheparticleProppantSettling0510152025300.000.501.001.502.002.503.003.504.0020/40Proppant30/50Proppant40/70ProppantASG,g/ccSettlingRateHighStrengthIntermediateStrengthLightweight/RCS/Sand40/70LWC/RCS/Sand2.01.25SettlingRatesComparisonBasedonSLB’s“iHandbook”,singleparticlesettling,60F(In2%KCLFluid)Sizevsdensity:A40/70LWC/RCS/Sandsettlesslowerthana20/401.75ASGproppantIntermediateDensityIfyourdadisanengineer,whatdoyoudoforyourschoolsciencefairprojects?Howdoestemperatureaffectviscosity?ProppantSettling/Transport•Stoke’sLaw:Assumeslaminarsettling,stagnantliquid,singlesphericalparticles,noparticleinteractionandnowalleffects.•Reality:Thereisturbulentflow,particle-particleinteractionandsignificantwalleffects.•Transport/Settlinggovernedby:Equilibriumbedheight,fluidizationandsedimentationEquilibriumBedHeight•StimLabvideoofproppanttransportinslickwaterConditions:•1cp•20/40sand•10gpm•1ppg•3evenlyspacedperfs•Slotwidth8mm(0.315inch)Observations:•Turbulence•Voidnearwellbore•Proppantdropsquicklyfromsuspension•QuicklyreachesequilibriumFluidization(Lift)Fluidization(Lift)andSedimentation(Drag)ProppantSettling/TransportEquilibriumBedHeightCourtesyStimLabSweepstage–cleanfluiderosion•StimLabvideoofproppanttransportinslickwaterConditions:•1cp•Cleanfluid(nosand)•10gpm•1ppg•3evenlyspacedperfs•Slotwidth8mm(0.315inch)Observations:•Erosion•Transportviasaltation•SlowlyreachesequilibriumAftercirculatingcleanfluidfor…4minutes14minutes24minutesWhydowepump“sweeps”…CourtesyStimLabWhathappenstoTailinProppants?(FromPatankar,2002andKerns,Perkins,andWyant,1959)EquilibriumheightNewEquilibriumheightEarlyproppant(i.e.40/70)Tail-inproppant(i.e.20/40)AsdocumentedinSPE110451EquilibriumheightNewEquilibriumheight20/40ELWC30/50ELWCAsdocumentedinSPE110451ProppantSettling/Transport•StokesLawisgreatforcomparingsettlingratebetweenproppants,fluids,rates,etc.•Proppanttransportisdominatedbyfluidizationandsedimentation,notlaminarsettling.•Proppantlikelybeingtransportedfurtherthanwemightimagine(SPE110809)–40/70sizedtracerfound800’offset–100Meshtracerfound1200’offsetProppantConductivitywfcf=kf*wfkfIsConductivityimportantinSlickwaterfracs?154057206854310225141085547243930100020003000400050006000EffectiveConductivity(md-ft)ISO13503-5TestInertialFlowwithNon-DarcyEffectsMultiphaseFlowLowerAchievedWidth(1lb/sqft)FinesMigration/CyclicStressJordanSandLightweightCeramicCumulativeConductivityReductions0.0001D-m0.029D-mConditions:YM=5e