叠前弹性波逆时深度偏移及波场分离技术探讨  

THE DISCUSSION OF REVERSE TIME DEPTH MIGRATION AND WAVEFIELD SEPARATION FOR PRESTACK ELASTIC DATA

作　　者：李文杰[1] 魏修成[1] 宁俊瑞[1] 张建伟[1] 王红旗[1] 

机构地区：[1]中国石化石油勘探开发研究院,北京100083

出　　处：《物探化探计算技术》2008年第6期447-456,共10页Computing Techniques For Geophysical and Geochemical Exploration

基　　金：国家"863"科技攻关项目(2006AA06Z203)

摘　　要：这里探讨了Sun和McMechan提出的叠前弹性波标量逆时深度偏移方法,即在地表附近,对地表接收到的弹性波波场分量进行波场逆时延拓,然后分别对在波场延拓过程中通过波场分离得到的纯纵、横波反射波场进行偏移。在模型中,每个网格点的纵、横波成像时间,为震源到该网格点的纵波初至时间。利用纵波速度模型和声波传播方程的有限差分解,对反射纵波进行逆时延拓和成像,利用横波速度模型和声波传播方程的有限差分解,对转换横波进行逆时延拓和成像,并在偏移前进行极性校正。然后,在Sun和McMechan偏移成像方法的基础上,提出了直接偏移成像方法,即对地表接收到的弹性波波场分量在整个模型范围内进行波场逆时延拓。在波场延拓过程中,对符合成像条件的网格点进行波场分离、偏移成像和转换波极性校正。最后,通过数值模拟对二种偏移成像方法的结果进行了比较。In the paper,the scheme for scalar reverse-time depth migration of prestack ealastic seismic data by Sun and McMechan is discussed,that is,the migration of pure P-and S-waves extracted by wavefields separation during(shallow)extrapolation of the elastic data recorded at the earth' surface,and for both P-to-P and P-to-S converted reflected waves,the imaging time at each point is the P-wave traveltime from the source to that point.the extracted P-wave is reverse-time extrapolated and imaged with a P-velocity model using a finite difference solution of the scalar wave equation,the extracted S-wave is reverse-time extrapolated and imaged similarly,but with an S-velocity model,and converted S-wave data requires a polarity correction prior to migration to ensure constructive interference between data from adjacent source.Then,on the basis of imaging scheme offered by Sun and McMechan,a new imaging scheme called direct migration and imaging was offered,which implemented wavefields separation and imaging and converted S-wave's polarity correction for those points satisfying imaging condition during extrapolation of the elastic data recorded at the earth' surface with entire velocity model.Finally,the results obtained with the two imaging schemes were compared.

关 键 词：各向同性介质 弹性波 纵波 转换横波 波场分离 逆时深度偏移 

分 类 号：P631.412[天文地球—地质矿产勘探]