逆时偏移剖面假象产生机制及其消除方法
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摘要
逆时偏移是实现地震偏移成像的有效手段,逆时偏移采用双程波方程,允许波沿各个方向传播,对地下介质没有倾角限制,偏移精度较高,适用于速度任意变化的模型。可是在逆时偏移过程中,会受到各种因素的影响,导致成像剖面中存在着一些偏移假象,因此分析这些假象产生的机制和研究其消除方法是逆时偏移成像的关键问题。从偏移假象产生的机制出发,重点分析了逆时偏移假象产生的各种原因,主要包括直达波的影响、边界反射的影响,并针对这些原因提出了解决的方法;特别针对成像条件引入的低频噪声,采用了拉普拉斯滤波算法消除噪声。应用结果表明,该算法有高通滤波的功能,但比高通滤波更平滑,效果较好。
Reverse-time migration was an effective way for seismic migration image,the reverse-time migration used dual wave equation,allowed waves spreading in all directions without restrictions on dip angles to underground medium.It was suitable for any speed-changing models with high accuracy.But in the reverse-time migration process,it would be affected by various factors,therefore some migration illusions were caused in imaging profiles,so analyzing these mechanisms of the illusions and studying its elimination methods were the key problems of the reverse-time migration.Based on the mechanism of migration illusion,all kinds of causes of the reverse-time migration which included the influences of the direct wave and boundary reflection were emphatically analyzed.Based on the analysis,some methods are proposed according to these causes and Laplace filtering algorithm is used for removing the low frequency noise introduced by imaging conditions.Application results show that the algorithm has high-pass filter function,but it is much smoother and effect is better than that of high-pass filter.
Reverse-time migration was an effective way for seismic migration image,the reverse-time migration used dual wave equation,allowed waves spreading in all directions without restrictions on dip angles to underground medium.It was suitable for any speed-changing models with high accuracy.But in the reverse-time migration process,it would be affected by various factors,therefore some migration illusions were caused in imaging profiles,so analyzing these mechanisms of the illusions and studying its elimination methods were the key problems of the reverse-time migration.Based on the mechanism of migration illusion,all kinds of causes of the reverse-time migration which included the influences of the direct wave and boundary reflection were emphatically analyzed.Based on the analysis,some methods are proposed according to these causes and Laplace filtering algorithm is used for removing the low frequency noise introduced by imaging conditions.Application results show that the algorithm has high-pass filter function,but it is much smoother and effect is better than that of high-pass filter.
引文
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[15]丁亮,刘洋.逆时偏移成像技术研究进展[J].地球物理学进展,2011,26(3):1085～1100.
[2]Chang W F,McMechan G A.Elastic reverse-time migration[J].Geophysics,1987,52(4):1365～1378.
[3]Yoon K,Marfurt K J.Reverse-time migration using the Poynting vector.Exploration Geophysics,2006,37(1):102～107.
[4]Liu Faqi,Zhang,Guanquan,Morton S A,et al.An effective imaging condition for reverse-time migration using wavefield decomposi-tion[J].Geophysics,2011,76(1):S29～S39.
[5]Mulder W A,Plessix R E.A comparison between one way and two way wave equation migtation[J].Geophysics,2004,69(6):1491～1504.
[6]Valenciano A A,Biondi B.Deconvolution imaging condition for reverse-time migration[J].Stanford Exploration Project,2002,Re-port 112:83～96.
[7]Liu Faqi,Zhang G,Morton S A,et al.Reverse-time migration using one-way wavefield imaging condition[A].2007SEG AnnualMeeting[C].San Antonio,2007-09-23～28.
[8]Guitton A,Kaelin B.Least-squares attenuation of reverse-time migration artifact[J].Geophysics,2004,69(6):1491～1504.
[9]Rickett J,Sava P.Offset and angle-domain common image-point gathersfor shot-profile migration[J].Geophysics,2002,67(7):883～889.
[10]Fletcher R P,Fowler P J.Suppressing unwanted internal reflections in prestack reverse-time migration[J].Geophysics,2006,71(6):79～82.
[11]红伟,刘洪,邹振.地震叠前逆时偏移中的去噪与存储[J].地球物理学报,2010,53(9):2171～2180.
[12]张军华,吕宁,田连玉,等.地震资料去噪方法技术综述评述[J].地球物理学进展,2006,21(2):546～553.
[13]杨仁虎,常旭,刘伊克.叠前逆时偏移影响因素分析[J].地球物理学报,2010,53(8):1902～1913.
[14]陈可洋.基于高阶有限差分的波动方程叠前逆时偏移方法[J].石油物探,2010,49(2):153～157.
[15]丁亮,刘洋.逆时偏移成像技术研究进展[J].地球物理学进展,2011,26(3):1085～1100.
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