Electrical_Logging

1OpenHoleElectricalLoggingLecturePresentationOctober18,21,and23,2002CarlosTorres-Verdín,Ph.D.AssistantProfessorPGE368Fall2002SemesterObjectives:•Tounderstandthephysicalprinciplesbehindtheoperationoflaterologandinductiontools,•Tounderstandtheprinciplesbehindtheinterpretationofapparentresistivitycurvesacquiredwithlaterologandinductiontools,•Tounderstandtheimportanceofenvironmentalcorrections,and•TointroducethephysicalprinciplesbehindtheoperationofLWDresistivitytools.2ComplementaryReadingAssignments:1.Bassiouni,Z.,1994,Theory,Measurement,andInterpretationofWellLogs,Chapter5:“ResistivityLogs.”2.Schlumberger’sComputerAnimatedPresentationsonInductionPrinciplesandLaterologPrinciplesavailablefromourcoursewebsite.OpenHoleBoreholeEnvironment3Open-HoleLoggingEnvironmentDynamicMudFiltrateInvasionandMudCakeBuildupSource:OilfieldReview,SchlumbergerLABORATORYSAMPLEBrine-WaterSaturation+-++++----VIR=VIR4ELECTRICALLOGGINGTOOLSInductionGalvanic(Laterolog)LowFrequencyExcitation:10Hz–500KHzELECTRICALLOGGINGTOOLSInductionLaterologElectricalConductivityofMudisanImportantIssue5250cm200150100500cm80cm80cm40cm30cm20cm60cm5cm2cm0cmINDUCTIONLOGLATEROLOGNEUTRONGAMMARAYDENSITYSONICMICRORESISTIVITYMICROLOGDIPMETERDEPTHOFINVESTIGATIONRESOLUTIONRESISTIVITYRADIOACTIVITYRESISTIVITYACOUSTICLoggingToolsINDUCTIONvs.LATEROLOG,When?6NORMALMEASUREMENTINABOREHOLEResistivityinaHomogeneousMedium−=====−∫∞IrdrdVRIVrRrRIrdrRIVdrrRIdVr22244444πππππCurrentlinesEquipotentialspheres7LATERALMEASUREMENTGUARDEDELECTRODEMEASUREMENT816”ShortNormal-1979•1927:1stwirelineresistivity•1stresistivitywhiledrilling•Rapparent=GV/I•Requiresconductive,water-baseddrillingfluid–LargeboreholeeffectslimitrangeRbR20Rb–Lowqualitysuitableforcorrelationandresistivitytrends–Insulationpronetofailure–ObsoletetechnologyLATEROLOG79DUALLATEROLOGLATEROLOG(GALVANIC)TOOLS10LATEROLOGTOOLCONFIGURATIONACTUALTOOLELECTRICALCONDUCTIONPHENOMENALaterologTools11LATEROLOGTOOLDifferentCurrentFocusingStrategiesLLDCORRECTIONCHARTFORBOREHOLEEFFECTS12LLDCORRECTIONCHARTFORINVASIONEFFECTSLLDCORRECTIONCHARTFORBEDTHICKNESS13LLSCORRECTIONCHARTFORBEDTHICKNESSMICROLATEROLOGDEVICE:aPadTool14MSFLTOOL:aMicro-LaterologDeviceFORMATIONMICRO-IMAGINGTOOL15PHYSICALPRINCIPLEOFINDUCTIONTOOLSPHYSICALPRINCIPLEOFINDUCTIONTOOLS16INDUCTIONSOUNDINGPHYSICALPRINCIPLEOFINDUCTIONTOOLS17DualPhasorArrayInductionMulti-FrequencyAcquisitionPRINCIPLEOFINDUCTIONFOCUSING18INDUCTIONTOOLSENSITIVITYIdealRadialGeometricFactorsActualRadialGeometricFactors19SENSITIVITIESFORDIFFERENTCOILSUBARRAYSLINEARAPPROXIMATIONTHEORY(GeometricFactorApproximation)20FOCUSEDSENSITIVITYFUNCTIONSSKINEFFECTCORRECTION(CorrectionforFrequency-DependentPropagationEffects)21BOREHOLECORRECTION(CorrectionforMudConductivityAndBoreholeSize)BOREHOLECORRECTION(CorrectionforMudConductivityAndBoreholeSize)22BEDTHICKNESSCORRECTION(InductionLog)INVASIONCORRECTION(InductionLog)23SUMMARYApproximateInterpretationCycleEXAMPLESkinandBoreholeCorrectedInductionCurves24EXAMPLEFocusedInductionCurvesMODERNINTERPRETATIONTECHNIQUES25COMPREHENSIVEINTERPRETATIONPROCESS(NumericalSimulationandInversion)EXAMPLE2-DInversionResults26LWDRESISTIVITYTOOLS16”ShortNormal-1979•1927:1stwirelineresistivity•1stresistivitywhiledrilling•Rapparent=GV/I•Requiresconductive,water-baseddrillingfluid–LargeboreholeeffectslimitrangeRbR20Rb–Lowqualitysuitableforcorrelationandresistivitytrends–Insulationpronetofailure–Obsoletetechnology272MHzPropagation-1984•1967patentbyM.Gouilloud•TransverseE-field•Worksinconductiveorinsulatingdrillingfluids•Smallboreholeeffectsinsmoothboreholes•1stquantitativeLWDresistivitymeasurement•~0.1–200ohm-mrange2MHzPropagation-1988•Symmetricarray-increasedaccuracy-reducedeffectsinrugoseholes•TworesistivitiesderivedfromPhaseShiftandAttenuation•Dualradialdepths-of-investigation•Anisotropicformations28Loopantennaslocatedunderslottedmetalshields.Close-UpofTool•PhaseShiftprovidesashallowresistivitywithhighaxialresolution•AttenuationprovidesadeepresistivitywithloweraxialresolutionDualDepths29AdvancesinPropagationResistivity•1991–Arraywith4depths-of-investigation•1995–Arraywith10depths-of-investigation•1995–Dualfrequencies400kHzand2MHz•Differentsizedrillcollars(3”to9”OD)1993:ToroidalResistivity•Electrodesheldatcollarpotential¤tsmeasured•ImprovesS/N,dynamicrange&provideshighspatialresolution•1stazimuthalresistivity•Providesboreholeimagesanddip•Multipledepths-of-investigation•Activefocusingtechnique•0.1-20,000ohm-mrange•MinimalboreholeeffectsRbR100,000Rb306.75”ToroidalResistivityButtonsToroidRingToroidLocationofdrillbitBoreholeResistivityImaging•Eachbuttonscans360°ascollarrotates•Stackedscansprovidecontinuousimage•Geologicalfeatures:–Beds–Dippingformations–Fractures–Faults•Geosteering31Acknowledgements•Schlumberger•BakerAtlas•Repsol-YPF