面向崎岖海底界面的声-弹最小二乘偏移  

Least-squares reverse time migration in acoustic-elastic coupling media with irregular seabed interfaces

作　　者：柳世光[1] 孙晶波[1] 张东伟[1] 张高[1] 吴佳乐[1] 袁安龙 LIU ShiGuang;SUN JingBo;ZHANG DongWei;ZHANG Gao;WU JiaLe;YUAN AnLong(PetroChina Liaohe Oilfield Branch,Panjin 124010,China)

机构地区：[1]中国石油辽河油田分公司,盘锦124010

出　　处：《地球物理学进展》2024年第2期851-866,共16页Progress in Geophysics

基　　金：辽河油田科技专项“复杂目标区地震勘探关键技术研究”(2023KJZX-01)资助。

摘　　要：在海洋环境中,地震波通过声波介质和弹性波介质进行传播.在海水层中,地震波以纵波的声波形式传播;而在下伏海底构造层中,地震波以既有纵波又有横波的弹性波形式传播.海底界面存在多种干扰波.本文推导出适用于起伏海底界面的声-弹耦合方程,旨在消除起伏海底界面所引起的散射和绕射干扰,从而实现声波场和弹性波场之间的稳定传递和转换.为解决起伏海底界面所产生的虚假散射噪声问题,本文提出了分层贴体网格剖分策略,通过坐标变换将起伏海底界面转换为水平海底界面,将物理域中的贴体网格转换为计算域中的矩形网格,以消除起伏海底和复杂构造的影响.模型测试结果表明,本文方法能够准确模拟起伏海底声-弹耦合介质的波场传递,产生稳定且清晰的波形.与传统的矩形网格声-弹耦合和单一弹性波方法相比,起伏海底声-弹耦合介质的最小二乘逆时偏移成像结果在信噪比和分辨率方面有显著的提高.In the marine environment,seismic waves propagate through both acoustic and elastic wave media.In the seawater layer,seismic waves propagate in the form of longitudinal acoustic waves,while in the submarine tectonic layer,seismic waves propagate in the form of elastic waves with both longitudinal and transverse waves.A variety of interference waves exist at the seafloor interface.In this paper,the coupled acoustic-elastic equations applicable to the undulating seafloor interface are derived,aiming at eliminating the scattering and bypassing interference caused by the undulating seafloor interface,so as to realize the stable transmission and conversion between the acoustic and elastic wave fields.In order to solve the problem of false scattering noise generated by the undulating seafloor interface,this paper proposes a hierarchical veneer mesh dissecting strategy,which converts the undulating seafloor interface into a horizontal seafloor interface through coordinate transformation,and converts the veneer mesh in the physical domain into a rectangular mesh in the computational domain,so as to eliminate the influence of the undulating seafloor and the complex structure.The model test results show that the method can accurately simulate the wave field transfer in the undulating seafloor acoustic-elastic coupling medium and produce stable and clear waveforms.Compared with the traditional rectangular grid acoustic-elastic coupling and single elastic wave methods,the results of the least-squares inverse time offset imaging of the undulating seafloor acoustic-elastic coupling medium show a significant improvement in signal-to-noise ratio and resolution.

关 键 词：起伏地表 起伏海底 声-弹耦合 贴体网格 最小二乘逆时偏移 

分 类 号：P631[天文地球—地质矿产勘探]