一种改进的转换波快速成像方法研究（英文）
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摘要
常规转换波快速成像方法直接利用反传的纵波和转换横波进行联合成像,由于所有传播方向的波场均参与转换波成像,导致成像剖面存在大量背景干扰噪声。针对这一问题,本文从以下两个方面对常规方法进行改进。一方面,本文采用改进的空间域波场分离方法对原始弹性波场解耦,得到保幅的纵、横波场。另一方面,构建了基于方向行波分离的转换波成像条件,在成像过程中只利用同向传播波场进行互相关成像,有效消除了不同方向传播波场的成像假象;为了提高方向行波分离的效率,在波场反传时采用复数波场延拓技术对解耦的纵、横波场进行方向行波分离。模型试算结果表明,改进后的方法转换波成像精度高于常规方法。而且,由于其与震源无关的特性,该方法还具有在微地震及被动震源勘探中的应用潜力。
The conventional fast converted-wave imaging method directly uses backward Pand converted S-wavefield to produce joint images. However, this image is accompanied by strong background noises, because the wavefi elds in all propagation directions contribute to it. Given this issue, we improve the conventional imaging method in the two aspects. First, the amplitude-preserved P-and S-wavef ield are obtained by using an improved space-domain wavef ield separation scheme to decouple the original elastic wavef ield. Second, a convertedwave imaging condition is constructed based on the directional-wavefield separation and only the wavefields propagating in the same directions used for cross-correlation imaging, resulting in effectively eliminating the imaging artifacts of the wavefields with different directions; Complex-wavefi eld extrapolation is adopted to decompose the decoupled P-and S-wavefield into directional-wavefields during backward propagation, this improves the eff iciency of the directional-wavef ield separation. Experiments on synthetic data show that the improved method generates more accurate converted-wave images than the conventional one. Moreover, the improved method has application potential in micro-seismic and passive-source exploration due to its source-independent characteristic.
The conventional fast converted-wave imaging method directly uses backward Pand converted S-wavefield to produce joint images. However, this image is accompanied by strong background noises, because the wavefi elds in all propagation directions contribute to it. Given this issue, we improve the conventional imaging method in the two aspects. First, the amplitude-preserved P-and S-wavef ield are obtained by using an improved space-domain wavef ield separation scheme to decouple the original elastic wavef ield. Second, a convertedwave imaging condition is constructed based on the directional-wavefield separation and only the wavefields propagating in the same directions used for cross-correlation imaging, resulting in effectively eliminating the imaging artifacts of the wavefields with different directions; Complex-wavefi eld extrapolation is adopted to decompose the decoupled P-and S-wavefield into directional-wavefields during backward propagation, this improves the eff iciency of the directional-wavef ield separation. Experiments on synthetic data show that the improved method generates more accurate converted-wave images than the conventional one. Moreover, the improved method has application potential in micro-seismic and passive-source exploration due to its source-independent characteristic.
引文
Aki,K.,and Richards,P. G..,1980,Quantitative seismology:Theory and methods:W. H. Freeman&Co., San Francisco, USA.
Audebert,F.,Nichols,D.,Rekdal,T.,Biondo,B.,Lumley,D. E.,and Urdaneta, H,,1997,Imaging complex geologic structure with single-arrival Kirchhoff prestack depth migration:Geophysics,62(5), 1533-1543.
Baysal,E.,Kosloff, D. D.,and Sherwood,J. W. C.,1983, Reverse time migration:Geophysics,48(11),1514-1524.
Chang, W., and McMechan, G. A., 1987, Elastic reversetime migration:Geophysics, 52(10), 1365-1375.
Chang,W.,and McMechan,G. A.,1994,3D elastic prestack reverse-time depth migration:Geophysics,59(4),597-609.
Claerbout,J. F.,1970, Coarse grid calculations of waves in inhomogeneous media with application to delineation of complicated seismic structure:Geophysics, 35(3), 407-418.
Claerbout,J. F.,1971,Toward a unified theory of reflector mapping:Geophysics, 36(3), 467-481.
Chattopadhyay, S., and McMechan G. A., 2008, Imaging conditions for prestack reverse-time migration:Geophysics, 73(3), S81-S89.
Chen,T.,and He,B.,2014, A normalized wavefield separation cross-correlation imaging condition for reverse time migration based on Poynting vector:Applied Geophysics, 11(2), 158-166.
Du,Q.,Gong,X.,Zhang,M.,Zhu,Y.,and Fang,G.,2014a, 3D PS-wave imaging with elastic reverse-time migration:Geophysics,79(5),S173-S184.
Du,Q.,Zhang,M.,Chen,X.,Gong,X.,and Guo, C.,2014b, True-amplitude wavefield separation using staggered-grid interpolation in the wavenumber domain:Applied Geophysics, 11(4),437-446.
Du,Q.,Guo, C..,Zhao, Q.,Gong, X.,Wang C.,and Li,X.,2017, Vector-based elastic reverse time migration based on scalar imaging condition:Geophysics, 82(2),S111-S127.
Du,S.,Chen,J.,and Liu,H.,2011,Accuracy analysis of the optimal separable approximation method of one-way wave migration:Applied Geophysics,8(4),328336.
Fletcher, R. P.,Fowler,P. J.,Kitchenside,P.,and Albertin,U.,2006,Suppressing unwanted internal reflection in prestack reverse-time migration:Geophysics,71(6),E79-E82.
Gabor,D.,1946,Theory of communications:Part 1:The Analysis of Information:Journal of Institution of Electrical Engineers, 93(26), 429-441.
Hu,L.,and McMechan,G. A.,1987,Wave-field transformations of vertical seismic profiles:Geophysics, 52(3), 307-321.
Liu,F.,Zhang,G.,Morton, S. A.,and Leveille, J. P.,2011, An effective imaging condition for reverse-time migration using wavefield decomposition:Geophysics,76(1), S29-S39.
Liu,Y., 2014, Optimal staggered-grid finite-difference schemes based on least-squares for wave equation modelling:Geophysical Journal International, 197(2),1033-1047.
McMechan, G. A.,1983, Migration by extrapolation of time-dependent boundary values:Geophysical Prospecting, 31(3),413-420.
Morse,P. M.,and Feshbach,H.,1953,Methods of theoretical physics:McGraw-Hill Book Company,New York, USA.
Mulder,W. A.,and Plessix,R. E.,2004, A comparison between one-way and two-way wave-equation migration:Geophysics,69(6),1491-1504.
Nihei, K. T.,Nakagawa,S.,and Myer,L. R.,2001,Fracture imaging with converted elastic waves:Lawrence Berkeley National Laboratory, Berkeley,USA.
Nguyen, B. D.,and McMechan, G. A.,2015, Five ways to avoid storing source wavefield snapshots in 2D elastic prestack reverse time migration:Geophysics,80(1), S1-S18.
Qu, L.,Liu,Y.,and Yong,P.,2016, A Method for fast elastic wave imaging:78th EAGE Conference and Exhibition,Extend Abstracts,We SRS3 02.
Ren.,Z.,and Liu,Y., 2015, Acoustic and elastic modeling by optimal time-space-domain staggered-grid finitedifference schemes:Geophysics, 80(1), T17-T40.
Schneider, W., 1978, Integral formulation for migration in two and three dimensions:Geophysics,43(1),49-76.
Shabelansky, A. H.,Fehler,M. C.,and Malcolm, A.E.,2013, Converted phase seismic imaging of the Hengill region:southwest Iceland:AGU Fall Meeting,Extended Abstracts, A2461.
Shabelansky, A. H.,Malcolm, A. E.,and Fehler,M. C.,2015, Converted-phase seismic imaging amplitudebalancing source-independent imaging conditions:77th EAGE Conference and Exhibition, ExtendedAbstracts,We N106 02.
Shabelansky,A. H.,Malcolm,A. E.,and Fehler,M. C.,2017, Converted-wave seismic imaging:Amplitudebalancing source-independent imaging conditions:Geophysics,82(2),S99-S109.
Sun, R., and McMechan, G. A., 2001, Scalar reversetime depth migration of prestack elastic seismic data:Geophysics, 66(5), 1519-1527.
Virieux,J.,1986,P-SV wave propagation in heterogeneous media:Velocity-stress finite difference method:Geophysics,51(4),889-901.
Wang,W., McMechan,G. A.,Tang,C.,and Xie.,F.,2016, Up/down and P/S decompositions of elastic wavefields using complex seismic traces with applications to calculating Poynting vectors and angledomain common-image gathers from reverse time migrations:Geophysics,81(4),S181-S194.
Wu,X.,Liu.,Y., and Cai, X.,2017, Comparison of three elastic wavefield decomposition methods and their applications in multidirectional vector imaging:87th SEG Annual International Meeting, Expanded Abstracts, 2486-2490.
Xiao,X.,and Leaney,W. S.,2010, Local vertical seismic profiling(VSP)elastic reverse-time migration and migration resolution:Salt-flank imaging with transmitted P-to-S waves:Geophysics, 75(2), S35-S49.
Zhang,Q.,and McMechan,G. A.,2010,2D and3D elastic wavefield vector decomposition in the wavenumber domain for VTI media:Geophysics,75(3),5D13-D26.
Zhu, H.,2017, Elastic wavefield separation based on the Helmholtz decomposition:Geophysics,82(2),S173-S183.
Audebert,F.,Nichols,D.,Rekdal,T.,Biondo,B.,Lumley,D. E.,and Urdaneta, H,,1997,Imaging complex geologic structure with single-arrival Kirchhoff prestack depth migration:Geophysics,62(5), 1533-1543.
Baysal,E.,Kosloff, D. D.,and Sherwood,J. W. C.,1983, Reverse time migration:Geophysics,48(11),1514-1524.
Chang, W., and McMechan, G. A., 1987, Elastic reversetime migration:Geophysics, 52(10), 1365-1375.
Chang,W.,and McMechan,G. A.,1994,3D elastic prestack reverse-time depth migration:Geophysics,59(4),597-609.
Claerbout,J. F.,1970, Coarse grid calculations of waves in inhomogeneous media with application to delineation of complicated seismic structure:Geophysics, 35(3), 407-418.
Claerbout,J. F.,1971,Toward a unified theory of reflector mapping:Geophysics, 36(3), 467-481.
Chattopadhyay, S., and McMechan G. A., 2008, Imaging conditions for prestack reverse-time migration:Geophysics, 73(3), S81-S89.
Chen,T.,and He,B.,2014, A normalized wavefield separation cross-correlation imaging condition for reverse time migration based on Poynting vector:Applied Geophysics, 11(2), 158-166.
Du,Q.,Gong,X.,Zhang,M.,Zhu,Y.,and Fang,G.,2014a, 3D PS-wave imaging with elastic reverse-time migration:Geophysics,79(5),S173-S184.
Du,Q.,Zhang,M.,Chen,X.,Gong,X.,and Guo, C.,2014b, True-amplitude wavefield separation using staggered-grid interpolation in the wavenumber domain:Applied Geophysics, 11(4),437-446.
Du,Q.,Guo, C..,Zhao, Q.,Gong, X.,Wang C.,and Li,X.,2017, Vector-based elastic reverse time migration based on scalar imaging condition:Geophysics, 82(2),S111-S127.
Du,S.,Chen,J.,and Liu,H.,2011,Accuracy analysis of the optimal separable approximation method of one-way wave migration:Applied Geophysics,8(4),328336.
Fletcher, R. P.,Fowler,P. J.,Kitchenside,P.,and Albertin,U.,2006,Suppressing unwanted internal reflection in prestack reverse-time migration:Geophysics,71(6),E79-E82.
Gabor,D.,1946,Theory of communications:Part 1:The Analysis of Information:Journal of Institution of Electrical Engineers, 93(26), 429-441.
Hu,L.,and McMechan,G. A.,1987,Wave-field transformations of vertical seismic profiles:Geophysics, 52(3), 307-321.
Liu,F.,Zhang,G.,Morton, S. A.,and Leveille, J. P.,2011, An effective imaging condition for reverse-time migration using wavefield decomposition:Geophysics,76(1), S29-S39.
Liu,Y., 2014, Optimal staggered-grid finite-difference schemes based on least-squares for wave equation modelling:Geophysical Journal International, 197(2),1033-1047.
McMechan, G. A.,1983, Migration by extrapolation of time-dependent boundary values:Geophysical Prospecting, 31(3),413-420.
Morse,P. M.,and Feshbach,H.,1953,Methods of theoretical physics:McGraw-Hill Book Company,New York, USA.
Mulder,W. A.,and Plessix,R. E.,2004, A comparison between one-way and two-way wave-equation migration:Geophysics,69(6),1491-1504.
Nihei, K. T.,Nakagawa,S.,and Myer,L. R.,2001,Fracture imaging with converted elastic waves:Lawrence Berkeley National Laboratory, Berkeley,USA.
Nguyen, B. D.,and McMechan, G. A.,2015, Five ways to avoid storing source wavefield snapshots in 2D elastic prestack reverse time migration:Geophysics,80(1), S1-S18.
Qu, L.,Liu,Y.,and Yong,P.,2016, A Method for fast elastic wave imaging:78th EAGE Conference and Exhibition,Extend Abstracts,We SRS3 02.
Ren.,Z.,and Liu,Y., 2015, Acoustic and elastic modeling by optimal time-space-domain staggered-grid finitedifference schemes:Geophysics, 80(1), T17-T40.
Schneider, W., 1978, Integral formulation for migration in two and three dimensions:Geophysics,43(1),49-76.
Shabelansky, A. H.,Fehler,M. C.,and Malcolm, A.E.,2013, Converted phase seismic imaging of the Hengill region:southwest Iceland:AGU Fall Meeting,Extended Abstracts, A2461.
Shabelansky, A. H.,Malcolm, A. E.,and Fehler,M. C.,2015, Converted-phase seismic imaging amplitudebalancing source-independent imaging conditions:77th EAGE Conference and Exhibition, ExtendedAbstracts,We N106 02.
Shabelansky,A. H.,Malcolm,A. E.,and Fehler,M. C.,2017, Converted-wave seismic imaging:Amplitudebalancing source-independent imaging conditions:Geophysics,82(2),S99-S109.
Sun, R., and McMechan, G. A., 2001, Scalar reversetime depth migration of prestack elastic seismic data:Geophysics, 66(5), 1519-1527.
Virieux,J.,1986,P-SV wave propagation in heterogeneous media:Velocity-stress finite difference method:Geophysics,51(4),889-901.
Wang,W., McMechan,G. A.,Tang,C.,and Xie.,F.,2016, Up/down and P/S decompositions of elastic wavefields using complex seismic traces with applications to calculating Poynting vectors and angledomain common-image gathers from reverse time migrations:Geophysics,81(4),S181-S194.
Wu,X.,Liu.,Y., and Cai, X.,2017, Comparison of three elastic wavefield decomposition methods and their applications in multidirectional vector imaging:87th SEG Annual International Meeting, Expanded Abstracts, 2486-2490.
Xiao,X.,and Leaney,W. S.,2010, Local vertical seismic profiling(VSP)elastic reverse-time migration and migration resolution:Salt-flank imaging with transmitted P-to-S waves:Geophysics, 75(2), S35-S49.
Zhang,Q.,and McMechan,G. A.,2010,2D and3D elastic wavefield vector decomposition in the wavenumber domain for VTI media:Geophysics,75(3),5D13-D26.
Zhu, H.,2017, Elastic wavefield separation based on the Helmholtz decomposition:Geophysics,82(2),S173-S183.