表驱Kirchhoff叠前时间偏移角度域成像方法
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摘要
为解决垂向变速介质中的射线弯曲效应问题,获得可直接用于AVO分析和反演的角度域共成像点道集,提出了一种基于射线追踪的表驱Kirchhoff叠前时间偏移方法。方法实现的基本原理是:首先基于横向均匀介质中的反射时距关系,利用改进的两点射线追踪算法建立走时和反射张角的数值表;然后在偏移过程中利用该数值表得到成像孔径内各反射路径对应的双程走时与入射角信息;进而通过脉冲响应叠加方法得到角度域共成像点道集和偏移成像剖面。由于加权函数部分考虑了射线弯曲效应的影响,因此更有利于振幅的相对保真。角度域共成像点道集波形拉伸效应的时不变特征也有利于后续的波形恢复处理。理论模型和实际地震资料验证了该方法的可行性。
For dealing with ray-bending effect in vertically varied velocity media and directly providing the common imaging point gathers within angle-domain for AVO analysis and inversion,the table- driven Kirchhoff pre-stack time migration based on ray tracing al- gorithm was proposed.The basic principles are that,according to the reflection time-distance equation in laterally homogeneous media,numerical tables of travel-time and reflecting angle are es- tablished through improved two points ray tracing algorithm,and then,during the course of migration,the information of two-way travel-time and incidence angle of each reflection path in imaging aperture can be obtained from these tables,finally,the angle-do- main common-image gathers and migration sections are obtained by using the impulse responses stacking method.For partially consid- ering the ray-bending effect into the weighting function,the ima- ging amplitudes should be more accurate.Moreover,the time in- variant feature of waveform stretching in angle domain is beneficial to the sequent waveform correction.Test results of synthetic data and actual seismic data have verified the feasibility of this method.
For dealing with ray-bending effect in vertically varied velocity media and directly providing the common imaging point gathers within angle-domain for AVO analysis and inversion,the table- driven Kirchhoff pre-stack time migration based on ray tracing al- gorithm was proposed.The basic principles are that,according to the reflection time-distance equation in laterally homogeneous media,numerical tables of travel-time and reflecting angle are es- tablished through improved two points ray tracing algorithm,and then,during the course of migration,the information of two-way travel-time and incidence angle of each reflection path in imaging aperture can be obtained from these tables,finally,the angle-do- main common-image gathers and migration sections are obtained by using the impulse responses stacking method.For partially consid- ering the ray-bending effect into the weighting function,the ima- ging amplitudes should be more accurate.Moreover,the time in- variant feature of waveform stretching in angle domain is beneficial to the sequent waveform correction.Test results of synthetic data and actual seismic data have verified the feasibility of this method.
引文
1 Fowler P J,Mobley E.The importance of anisotropy and turning rays in prestack time migration[J].Ex- panded Abstracts of 74~(th) Annual Internat SEG Mtg, 2004,1 013～1 016
2王棣，王华忠．叠前时间偏移方法综述[J]．勘探地球物理进展，2004，27(5)：310～320
3 Alkhalifah T,Tsvankin I.Velocity analysis for trans- versely isotropicmedia[J].Geophysics,1995,60(5): 1 550～1 566
4 Sun C,Martinez R D.3D Kirchhoff PS-wave prestack time migration for v(z)and VTI media[J].Expanded Abstracts of 73~(rd) Annual Internat SEG Mtg,2003, 957～960
5 Castle R J.A theory of normal moveout[J].Geophys- ics,1994,59(6):983～999
6 Zheng Y.Seismic azimuthal anisotropy and fracture a- nalysis from PP reflection data[D].Calgary:Univer- sity of Calgary,2006
7 Perez G,Marfurt K J.Improving lateral and vertical resolution of seismic images by correcting for wavelet stretch in common-angle migration[J].Geophysics, 2007,72(6):95～104
8 Walden A T.Making AVO sections more robust[J]. Geophysical Prospecting,1991,39(7):915～942
9 Zhang Y,Gray S,Young J.Exact and approximate weights for Kirchhoff migration[J].Expanded Ab- stracts of 70~(th) Annual Internat SEG Mtg,2000, 1 036～1 039
10 Dellinger J A,Gray S H,Murphy G E,et al.Efficient 2.5-D true-amplitude migration[J].Geophysics,2000, 65(3):943～950
11 Tygel M,Schleicher J,Hubral P.Pulse distortion in depth migration[J].Geophysics,1994,59(10): 1 561～1 569
12 Roy B,Anno P,Phillips C,et al.Analytic correction for wavelet stretch due to imaging[J].Expanded Ab- stracts of 75(th) Annual Internat SEG Mtg,2005, 234～237
13 Slotnick M M.Lessons in seismic computing,a memo- rial to the author[M].Lawrence:The Society of Ex- ploration Geophysicists,1959.1～268
14田玥，陈晓非．水平层状介质中的快速两点间射线追踪方法[J]．地震学报，2005，27(2)：147～154
15 Lee S,King D.Efficient true-amplitude weights in Kirchhoff time migration[J].Expanded Abstracts of 74~(th) Annual Internat SEG Mtg,2004,1 089～1 092
2王棣，王华忠．叠前时间偏移方法综述[J]．勘探地球物理进展，2004，27(5)：310～320
3 Alkhalifah T,Tsvankin I.Velocity analysis for trans- versely isotropicmedia[J].Geophysics,1995,60(5): 1 550～1 566
4 Sun C,Martinez R D.3D Kirchhoff PS-wave prestack time migration for v(z)and VTI media[J].Expanded Abstracts of 73~(rd) Annual Internat SEG Mtg,2003, 957～960
5 Castle R J.A theory of normal moveout[J].Geophys- ics,1994,59(6):983～999
6 Zheng Y.Seismic azimuthal anisotropy and fracture a- nalysis from PP reflection data[D].Calgary:Univer- sity of Calgary,2006
7 Perez G,Marfurt K J.Improving lateral and vertical resolution of seismic images by correcting for wavelet stretch in common-angle migration[J].Geophysics, 2007,72(6):95～104
8 Walden A T.Making AVO sections more robust[J]. Geophysical Prospecting,1991,39(7):915～942
9 Zhang Y,Gray S,Young J.Exact and approximate weights for Kirchhoff migration[J].Expanded Ab- stracts of 70~(th) Annual Internat SEG Mtg,2000, 1 036～1 039
10 Dellinger J A,Gray S H,Murphy G E,et al.Efficient 2.5-D true-amplitude migration[J].Geophysics,2000, 65(3):943～950
11 Tygel M,Schleicher J,Hubral P.Pulse distortion in depth migration[J].Geophysics,1994,59(10): 1 561～1 569
12 Roy B,Anno P,Phillips C,et al.Analytic correction for wavelet stretch due to imaging[J].Expanded Ab- stracts of 75(th) Annual Internat SEG Mtg,2005, 234～237
13 Slotnick M M.Lessons in seismic computing,a memo- rial to the author[M].Lawrence:The Society of Ex- ploration Geophysicists,1959.1～268
14田玥，陈晓非．水平层状介质中的快速两点间射线追踪方法[J]．地震学报，2005，27(2)：147～154
15 Lee S,King D.Efficient true-amplitude weights in Kirchhoff time migration[J].Expanded Abstracts of 74~(th) Annual Internat SEG Mtg,2004,1 089～1 092
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