弹性波全波形反演中时频域单频能量谱初始建模技术  

Establishment method of initial model for elastic full waveform inversion based on single-frequency energy spectrum in time-frequency domain

作　　者：李芳 任婷 黎孝璋 姜占东 李远芳 郭昊 LI Fang;REN Ting;LI Xiaozhang;JIANG Zhandong;LI Yuanfang;GUO Hao(CNOOC China Limited,Hainan Branch,Haikou,Hainan 570100,China;Ocean University of China,Qingdao,Shandong 266100,China)

机构地区：[1]中海石油(中国)有限公司海南分公司,海南海口570100 [2]中国海洋大学,山东青岛266100

出　　处：《中国海上油气》2024年第6期50-58,共9页China Offshore Oil and Gas

基　　金：中国海洋石油集团有限公司关键核心技术攻关项目“基于海底节点资料的模糊区、底辟带波及区地震成像和储层描述研究(编号:CNOOC-KJ GJHXJSGG YF 2022-01)”;有限公司综合科研项目“莺歌海盆地超压低渗气藏勘探开发关键技术研究(编号:KJZH-2023-2102)”部分研究成果。

摘　　要：弹性波全波形反演(EFWI)是一个高度病态的非线性过程,反演精度十分依赖初始纵横波速度模型的精度和多分量炮集中的可用低频成分。当初始模型精度过低且输入的三分量炮集中缺少有效的低频信息时,反演往往不能收敛于全局极小,导致反演失败。本文研究了一种基于时频域单频能量谱反演的EFWI初始模型构建方法:先利用S变换从缺失低频信息的炮集数据中提取不同频率的单频能量谱,然后推导了时频域能量谱反演的目标函数、梯度表达式以及伴随震源公式,实现了多分量数据的弹性波单频能量谱反演,以单频能量谱反演结果作为初始模型进行混合域多尺度EFWI,最终实现了低频信息缺失情况下多波数据的高精度的EFWI。模型数据测试结果表明:该方法能够在多分量地震数据缺失低频信息时反演得到良好的初始纵横波速度模型,进而提高EFWI的反演精度。Elastic full waveform inversion(EFWI)is a highly ill-conditioned nonlinear process,and its inversion accuracy heavily depends on the accuracy of the initial model of compression wave velocity and shear wave velocity as well as the available low-frequency components in multi-component shot gathers.When the accuracy of the initial model is too low,and the input three-component shot gathers lack effective low-frequency information,the inversion often cannot converge to the global minimum,which leads to inversion failure.The paper studies a method for constructing initial models of EFWI based on single-frequency energy spectrum inversion in time-frequency domain.Firstly,S-transform is used to extract single-frequency energy spectra of different frequencies from shot gathers which lack low-frequency information.The objective function,gradient expression,and accompanying seismic source formula for energy spectrum inversion in time-frequency domain are also derived,and then an elastic single-frequency energy spectrum inversion of multi-component data is achieved.By using the single-frequency energy spectrum inversion results as the initial models for multi-scale EFWI in the mixed domain,a high-precision EFWI of multi-component data is achieved in the absence of low-frequency information.The model testing results show that the method can establish a good initial model of compression wave velocity and shear wave velocity when multi-component seismic data lack low-frequency information,effectively improving the inversion accuracy of EFWI.

关 键 词：弹性波全波形反演 S变换 单频能量谱反演 低频模型 目标函数 

分 类 号：TE132.14[石油与天然气工程—油气勘探]