叠前逆时深度偏移中的激发时间成像条件  

Prestack reverse-time depth migration and the imaging condition

作　　者：丁仁伟[1] 李振春[1] 孙小东[1] 仝兆岐[2] 

机构地区：[1]中国石油大学(华东)地球资源与信息学院,东营257061 [2]中国石油大学(华东)计算机与通信工程学院,东营257061

出　　处：《地球物理学进展》2008年第6期1859-1865,共7页Progress in Geophysics

基　　金：国家自然科学基金(40474041);国家863专题(2006AA06Z206);CNPC中青年创新基金(04E7040);中原油田博士后科研工作站和CNPC物探重点实验室中国石油大学(华东)研究室联合资助

摘　　要：与其他偏移方法相比,逆时偏移基于精确的波动方程而不是对其近似,用时间外推来代替深度外推.因此,它具有良好的精度,不受地下构造倾角和介质横向速度变化的限制.激发时间成像条件的求取是叠前逆时偏移的难点之一,本文采用求解程函方程的方法得到地下各点的初至波走时,以此作为叠前逆时偏移的成像条件.基于任意矩形网格和局部平面波前近似的有限差分初至波走时计算方法精度较高并适用于强纵横向变速的复杂介质.试算结果表明,在复杂介质模型中利用叠前逆时深度偏移收到了很好的成像效果.Compared with the other migration methods, reverse-time migration is based on the accurate wave equation but not its approximate formula and extrapolates wave field along time axes instead of depth axes. So it has good precision and has no dip restriction or velocity variation restriction. Calculation on the excitation-time imaging condition is very important work in prestack reverse-time migration. Start from eikonal equation, derive primary wave traveltime of each point in the subsurface and take it as the imaging condition of prestack reverse-time migration. The finite- difference method of calculation on primary wave traveltime based on any rectangular grid and a local plane wavefront approximation has high precision and can apply to complex media with violent velocity variation. The results prove that perfect imaging result can be obtained from complex model using prestack reverse-time migration.

关 键 词：逆时偏移 激发时问成像条件 程函方程 初至波走时 

分 类 号：P631[天文地球—地质矿产勘探]