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1、The Marmousi2 Elastic Model and Synthetic Data,Gary Martin,GX TechnologyRobert Wiley and Kurt Marfurt,AGL/University of Houston,Outline,IntroductionThe Marmousi2 modelMarmousi2 acquisitionMarmousi2 synthetic dataProcessing and migration examplesConclusion,Introduction,This work has been performed as
2、 part of the Next Generation Numerical Modeling and Imaging project.New suite of shared seismic modelsUpdate the popular and very useful Marmousi model using modern computing power.,The Marmousi2 Model,Original Marmousi,Geologic ModelCreated in 1988 by IFPBased on real geology from West Africa(Angol
3、a)Complex model(160 layers)9.2 km x 3 kmSimulationAcoustic simulation using a second order(in time and space)finite difference algorithm4m grid size,frequencies up to 55HzMaximum offset 2.5 km,Marmousi2,ModelLarger model(2X length)Deep water(450m)Longer offsets(up to 17km)Hydrocarbons with AVO effec
4、tsStratigraphic features,Marmousi,Marmousi-2,Marmousi,Marmousi models,Lithology and Features,Layer Properties,Determined by lithology,fluid content,and original Marmousi P-wave velocity.,LithologiesSandShaleMarlSalt,FluidsWaterGasOil(varying GOR),P-wave Velocity,Extracted from original Marmousi mode
5、lModifications for Hydrocarbon saturated layersSalt velocity,reduced to 4500m/sVelocity parameterizationConstantsVertical velocity gradientsP-wave velocity is the source for both density and S-wave transforms,P-wave Velocity,km/s,1,5,4,2,3,S-wave Velocity,Determined directly from P-wave velocity usi
6、ng Greenburg and Castagna(1992)Sand:Vs=0.804Vp 856Shale:Vs=0.770Vp 867Limestone:Vs=1.017Vp 0.055Vp2 1030Marl:30%limestone,70%shaleUsing mixing laws and effective medium theory,m/s,S-wave Velocity,km/s,0,3,2,1,Density,Determined directly from P-wave velocity using Castagnas(1993)transforms Sand:r=0.2
7、736Vp.261Shale:r=0.2806Vp.265Limestone:r=0.3170Vp.225Marl:30%limestone,70%shaleUsing mixing laws and effective medium theory,g/cm3 and m/s,Density,g/cm3,1.0,3.0,2.5,1.5,2.0,2.0,Hydrocarbons,Gas and oil emplaced into some sand layers.5 gas sands3 oil sands1 oil and gas cap,Fluid substitution used to
8、provide realistic properties that will be useful for AVO calibration.Seismic responses verified using simplified models and ray-tracing.,Data Acquisition,Marmousi2 Acquisition,Acquisition objectivesElastic simulation.Simultaneous streamer,OBC,and VSP acquisition.Multi-component recording for OBC and
9、 VSPs.Record Wave-front snapshots.Reflecting boundary at free surface.,Acquisition Geometry,Source,An Ormsby wavelet with frequencies up to 80 Hz,(5-10,60-80).,Near field,Far field,Computation Considerations,Grid size To ensure adequate sampling(to prevent numerical problems)a grid size of 1.25m was
10、 required.,Marmousi grid:4m x 4m,Marmousi2 grid:1.25m x 1.25m,Computation,AlgorithmE3D:National Labs.elastic modeling code2nd order time,4th order space finite difference elastic modelingComputation TimeSun 6800 Starfire system at UH20 CPUs for 5 months4 CPU days per shotTotal hours 70,000 8 CPU yea
11、rs,Marmousi2 Synthetic Data,Synthetic Data,Wavefront snapshotsSynthetic Shot Records StreamerOBCVSP,Wave Propagation Example,2,Shot 2:Complex Geology,x=9000,Shot 2:Complex Geology,0,time,Shot 2:Complex Geology,0.25,time,Shot 2:Complex Geology,0.50,time,Shot 2:Complex Geology,0.75,time,Shot 2:Complex
12、 Geology,1.00,time,Shot 2:Complex Geology,1.25,time,Shot 2:Complex Geology,1.50,time,Shot 2:Complex Geology,1.75,time,Shot 2:Complex Geology,2.00,time,Shot 2:Complex Geology,2.25,time,Shot 2:Complex Geology,2.50,time,Shot 2:Complex Geology,2.75,time,Shot 2:Complex Geology,3.00,time,Shot 2:Complex Ge
13、ology,3.25,time,Shot 2:Complex Geology,3.50,time,Shot 2:Complex Geology,3.75,time,Shot 2:Complex Geology,4.00,time,Shot Record Examples,1,2,Shot 1:Streamer and OBC Pressure,-4 Offset(km)8-4 Offset(km)8,t(s),0,4,Streamer pressure,OBC pressure,Shot 1:OBC Velocity components,Vx,Vz,-4 Offset(km)8-4 Offs
14、et(km)8,t(s),0,4,Shot 1:VSP records at offset=500m,3.5 Z(km)0 3.5 Z(km)0 3.5 Z(km)0,t(s),0,4,pressure,Vx,Vz,Shot 2:Streamer and OBC Pressure,t(s),0,4,Streamer pressure,OBC pressure,-4 Offset(km)8-4 Offset(km)8,Shot 2:OBC Velocity components,t(s),0,4,-4 Offset(km)8-4 Offset(km)8,Vx,Vz,Shot 2:VSP reco
15、rds at offset=500m,t(s),0,4,pressure,Vx,Vz,3.5 Z(km)0 3.5 Z(km)0 3.5 Z(km)0,Data Sets,Four datasets are available from UH:Full dataset(all offsets,all components)Acoustic dataset(all offsets)A 6km acoustic towed streamer subsetWavefront snapshotsA Marmousi2 website is being createdwww.uh.edu/Geoscie
16、nces/Marmousi2?,Processing and Migration Examples,Processing and Migration Examples,Using the 6km acoustic streamer subsetMinimum processingCorrect for source/receiver depthsShift data by 72ms(correct for wavelet)NMO/StackPoststack time migrationPoststack depth migrationPrestack time migrationPresta
17、ck depth migration,Simple NMO/Stack,ProMAX Stolt PoSTM,ProMAX Kirchhoff PoSDM,PrimeTime Kirchhoff PreSTM,Primus Kirchhoff PreSDM,Shortest path,Primus Kirchhoff PreSDM,Max energy,Optimus Wave Equation PreSDM,Conclusion,Conclusion,A complex structure 2D elastic model with realistic hydrocarbons and st
18、ratigraphic features has been created.A high quality elastic finite difference synthetic data set has been created.Model and data are freely available.,Conclusion,UsesAVO calibrationVelocity estimationMigration algorithm evaluationMulti-component and VSP evaluationMultiple suppression,etc.LimitationsModel and data are 2D.,GX Technology CorporationDon Larson,GX TechnologyAline Bougeois,IFPFred Hilterman,GDC,Acknowledgements,
