地应力技术研究裂缝的渗透性

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FracturePermeability FromaJointtoaFaultFaultingiskeytoincreasingthepermeabilityofaformation TheCriticallyStressedFractureConceptPre-existingfracturesandfaultsareveryimportantincontrollingpermeabilityinmanyreservoirsModeIIandIIIfracturesthatareoptimallyorientedtotoday’sstressfieldtobeopeninshear(criticallystressedfractures)providethepermeablepathwaysforfluidflow.ModeIfractures(openingmodejoints)areunlikelytobeasimportantincontrollingflowasmodeIIandIIIshearfractures(faults)inmanyreservoirsunlesseffectivestressisextremelylow(i.e.,porepressureisclosetolithostatic).Wellboreimageloggingisneededtoprovidedetailedinformationaboutfracturesatdepth.The3-Dstressstateisanessentialcomponentoftheanalysisofcriticallystressedfracturesandfaults.Doesnotpredictfractureorientationsanddensities 3-DMohrCircle ts1s2s3Friction(m)s1s2s3s1s2s3tFriction(m)Friction(m)SHEARSTRESSEFFECTIVENORMNALSTRESSSHEARSTRESStSHEARSTRESSEFFECTIVENORMNALSTRESSConventionalThinking(veryrareinnature)FracturePermeabilityMechanismsMapviewoffracturesHydraulicallyConductive,CriticallyStressed(RepeatedFaultSlipIsPreservingPermeability)HydraulicallyNon-Conductive;StableFaultsMohr-CoulombCriterion RelationshipBetweenCritically-StressedFracturesandFluidFlowPermeableFractureImpermeableFracture CorrelationBetweenNaturalFracturesandReservoirFluidFlow FractureDiscriminationBasedonThermalPerturbationsintheBoreholeStatistically,thehydraulicallyconductivefracturesdisplayinganenhancementinpermeabilityarealsocriticallystressed BusinessImpact–PermeabilityEnhancementOptimizingwelltrajectoriestointersectpermeablefracturesetscanincreaseproductionratesbyanorderofmagnitude.Withknowledgeofthedistributionofcriticallystressedfracturesets,operatorscanoptimizehydrauliccommunicationwiththereservoir,ANDcansuccessfullyimplementenhancedrecoveryandredrillingstrategies.Understandingcriticallystressedfracturedistributioninreservoirscanhelptoavoidcostlydrillingproblemsassociatedwithcasingshear. PermeabilityofFracturedReservoirs-Workflow NaturalFractureCharacterization CaseStudy-Geothermal DixieValleyGeothermalProduction ConceptualModel ShminOrientationsfromImageAnalysis StressOrientationandMagnitudes Conductivevs.Non-ConductiveFractures CentralNevada–PermeabilityEnhancementBreakoutsrotateatactivefaultsduetolocalizedstressdropAdistinctcorrelationbetweencriticallystressedfracturesandhydraulicconductivityACTIVEFAULT BusinessImpact–CentralNevadaTheoperatorofthislargeGeothermalfieldcannowlocateanddesignproductionandinjectionwellstooptimizehydrauliccommunicationwiththereservoir.Knowledgeofwhichfractureandfaultsprovideconduitsforflowhasenabledtheoperatortodesignenhancedrecoveryandredrillingstrategies(massivehydrofracstimulationoperations,sidetracks).Itisnowpossibletoidentifylocationsanddepthswhereexcessivefluidlossesmightpresentadrillingproblem. CriticallyStressedFracturescanOccurinAllStressRegimes CompositeofFracturesFromThreeDifferentStressStates Oil-filledbrecciaMonetreyShaleSeismicactivityprovidesdirectevidenceofcriticallystressedfracturesandfaultsHydrocarbonSaturatedBrecciaZonesFromPt.ArguelloAreaoilstaining DST’sinWellAHighpermeabilityobtainedfromdrillstemtestsinWellAsuggestacorrelationofaclusteredfracturepopulationthatiswellorientedforslipinthePt.Arguellostrikeslipfaultingregime BusinessImpact–SantaMariaBasinCaliforniaTheoperatoroftheseoffshoreandonshorewellsmarkedlyimprovedtheirunderstandingoffracturepermeabilityintheSantaMariaBasin.CarefuldelineationoffracturesetswithinspecificlithologiesoftheMonetreysequenceprovidedanimportanttooltodistinguishzoneswherebrittlefracturingofthechertsanddolostonesdominatesthemoreductilemechanicalbehaviorofshales.Fluidmigrationpathwaysinthisbasinarelimitedtothesetofoptimallyoriented,criticallystressedfracturesinthemorebrittledolostonesandcherts.Thisdistinction,basedonthemechanicalbehaviorofthesefracturessets,enabledtheoperatorstopreciselyselectthedepthforwellplacement. NorthAmerica–ProductionEnhancementSHmaxorientationisstructurallycontrolled-needstressorientationmeasurementsatthewelllocationratherthanusingregionalstressdataProductionisenhancedwhenwellsaredrilled~70ºtotheNorthwest BusinessImpact–NorthAmericaSincetheapplicationofGMI’stechnologiestheoperatorsreportremarkablesuccess.Theoverallwellplacementstrategyhashada“100%economicsuccessrate,[productioninthis]structurehasperformedbetterthanyoumighthaveanticipated”.Productionincomparablehorizontalwellshasincreasedfrom~800BOPDto~5000BOPDKnowledgeofthestressfieldhasalloweddrillingofhighlysuccessfulhorizontalwellsinseveralfieldsutilizingthecritically-stressedfaulthypothesisofGMI.Knowledgeofthefullstresstensoralsoenabledtheoperatorstoselectwelltrajectoriesandmudweightsthatavoidedwellborestabilityproblemsandoptimizedhydraulicfracturingoperations. FracturePermeability-FinalRemarksAstrongcorrelationexistsbetweencriticallystressedfaultsandhydraulicconductivityinhighlyfracturedcrystallinerock.Thiscorrelationcanbeusedtohelppredictdrillingtrajectoriesthatwilloptimizereservoirdrainageaswellasimprovehydrofracturingefficiencyandsecondaryrecoveryefforts.Theseprinciplescanalsobeappliedtofaultsealintegrityandcolumnheight.Theymayalsobeusedtoassessfracture/faultreactivation