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1、Slipslidin'away-implicationsofvelocityanisotropyondepthimagingofseismicdataDonLawtonUniversityofCalgaryCalgary,Alberta,CanadaFold-faultResearchProject...youknowthecloseryourdestination,themoreyou’reslipslidin’away...(PaulSimon,1977)VerticalTransverseIsot
2、ropy(VTI)V(fast)90ε=ε=(ε=(V-V)/V9000δ=4[V/V-1]-[V/V-1]450900V(slow)0PhotocourtesyD.SprattIsotropicwavefrontε=0.0δ=0.0VVAnisotropicwavefront(VTI)ε=0.2δ=0.05V90V0Anisotropicwavefront(VTI)ε=0.2δ=−0.2V90V0Tiltedtransverseisotropy(TTI)wavefrontSlowFastGroupPh
3、aseImplementation–prestackKirchhoffsourcereceivermidpointAplanaticsurface•Raytracethroughvelocitymodelatallsourcesandreceivers•Creategriddedtraveltimetables•Foreachtrace,sumsourceandreceivertables•DistributeweightedtraceamplitudesoveraplanaticsurfacesFRP
4、phenolicTTIstepmodelFRPTTIstepmodel0m5100mAnisotropicV=2925m/s1500moε=0.22δ=0.10480m1580mMultichannelrecord,stepmodelBaseofanisotropiclayerTopstepBasestepIsotropicmigrationoperatormidpointAnisotropicmigrationoperatormidpointFRPTTIstepmodelShotpointgeopho
5、ne0mmidpoint5100m1500mAnisotropicSideslip480m1580mMigratedsection(isotropic)Depth(m)Migratedsection(anisotropic)Depth(m)Lateralpositionerrorintargethinterlandforelandt)Vs(fas(loVw)DEPTHImagedpositionActualposition(isotropic)Lawtonetal.,2001Thrustfaultmod
6、el(layeredfibreglass,homogeneous,anisotropic)0.0Distance(km)5.00.01.0Depth(km)2.0Migratedsection(isotropic)Migratedsection(anisotropic)IsotropicdepthmigrationDatacourtesyHusky&Talisman.Vestrumetal.,1999AnisotropicdepthmigrationDatacourtesyHusky&Talisman.
7、Vestrumetal.,1999TarataThrustZone,TaranakiBasinfromBlackburn(1998)Timemigration“imagingvelocity”Anisotropicdepthmigration[V,ε,δ,θ]0AzimuthalrefractionlinelayoutDipe4ik5otrSMultioffsetVSPVSPABwellV0(sV45t)lows(fa)90VConclusions•Clasticrocksareanisotropic•
8、Anisotropyimpactsdepthimaging•Depthandpositionerrorswilloccurifisotropicmigrationvelocitiesareused•Vεδθmodelsarerequiredformigration•ValuesofanisotropyparametersareneededAcknowledgementsRobVestrum,JenniferLeslie,GraziellaK
