伪深度域弹性波有限差分数值模拟及逆时偏移  

Elastic-wave numerical simulation and reverse time migration in pseudo-depth domain

作　　者：邹强 黄建平[1] 李庆洋 雍鹏 辛天亮 ZOU Qiang;HUANG Jianping;LI Qingyang;YONG Peng;XIN Tianliang(Geophysics Department,School of Geosciences,China University of Petroleum(East China),Qingdao,Shandong 266580,China;Geophysical Exploration Research Institute,Sinopec Zhongyuan Oilfield Company,Puyang,Henan 457001,China)

机构地区：[1]中国石油大学(华东)地球科学与技术学院地球物理系,山东青岛266580 [2]中国石化中原油田分公司物探研究院,河南濮阳457001

出　　处：《石油地球物理勘探》2020年第2期321-330,I0004,共11页Oil Geophysical Prospecting

基　　金：中国科学院战略性先导科技专项“深层结构RTM成像及裂缝预测-1(A)”(XDA14010303-1);国家自然科学基金优秀青年科学基金项目“油气勘探地球物理”(41922028);国家科技重大专项“基于多次散射理论的散射波地震成像技术”(2016ZX05014-001-008)联合资助。

摘　　要：有限差分法地震波场外推通常基于笛卡尔坐标系,当地下介质速度差异很大时,会导致波场的局部过采样现象,增加计算量。为此,将伪深度域的思想引入到弹性波有限差分数值模拟。首先通过坐标转换的链式法则,推导了深度域到伪深度域的坐标映射关系,获得了伪深度域下的弹性波方程(PDD-EWE),在保证精度的前提下,在伪深度域进行波场外推能减少大量内存占用;引入变长度差分算子,即在一定的误差范围内,根据速度的不同设计了不同长度的差分算子。模型测试结果表明,与常规深度域方法相比,伪深度域变长度差分算子弹性波正演模拟和成像算法在保证精度的前提下,既能减少内存占用又能提高计算效率。Wave field extrapolation using finite-difference method is usually accomplished in the Cartesian coordinate system.Oversampling may occur locally when subsurface velocity varies greatly;this will increase the workload of computation.To address this issue,we fulfill finite-difference numerical simulation in pseudo-depth domain.In accordance with the chain rule of coordinate conversion,we formulate the mapping relation between the Cartesian coordinate system and pseudo-depth domain as well as consequent elastic wave equation(PDD-EWE)in pseudo-domain.Memory consumption may be significantly reduced for wave field extrapolation in pseudo-depth domain,provided that the accuracy is guaranteed.A variable difference operator is adopted,and its length varies with velocity.The model tests show that for the similar accuracy,elasticwave forward modeling and imaging with a variable difference operator in pseudo-depth domain is better than conventional finite-difference method in depth domain in view of less memory consumption and higher computational efficiency.

关 键 词：弹性波 数值模拟 逆时偏移 伪深度域 变长度差分算子 内存占用 计算效率 

分 类 号：P631[天文地球—地质矿产勘探]