逆时偏移波场分解成像条件研究及应用  

Research and application of reverse time migration using wavefielddecomposition imaging condition

作　　者：许璐[1] 张永生 李博[1] 刘定进[1] 王小青[1] XU Lu;ZHANG Yong-sheng;LI Bo;LIU Ding-jin;WANG Xiao-qing(Sinopec Geophysical Research Institute,Nanjing 211103,China;Research Institute of Petroleum Exploration and Production,Sinopec Northwest Company,rümqi 830011,China)

机构地区：[1]中国石油化工股份有限公司石油物探技术研究院,南京211103 [2]中国石化西北油田分公司研究院,乌鲁木齐830011

出　　处：《地球物理学进展》2019年第4期1541-1547,共7页Progress in Geophysics

基　　金：国家重点研发计划(2017YFC0602804-02)资助

摘　　要：逆时偏移是处理复杂高陡构造成像的一种有效技术.然而,互相关成像条件会在成像过程中产生低波数、强振幅的偏移噪声,降低成像精度.实际数据应用结果表明,叠后滤波方法虽然高效但会损失成像剖面中的低波数信息,影响着高陡断裂构造的成像质量.常规基于波场分解的逆时偏移方法可在消除偏移噪声的同时保持数据频带不受损失,但对存储及计算有较高要求,不能满足实际海量数据的生产应用.为了兼顾效率与效果,本文在分析了常规波场分解逆时偏移方法的基础上,在成像过程中采用基于解析波场隐式分解的逆时偏移成像条件,高效地实现了时间-空间域波场的隐式分解,提高波场分解效率的同时显著改善了成像质量.理论模型测试和实际数据应用验证了方法的正确性和有效性.Reverse time migration based on two-way wave equation is an effective method to deal with steeply dipping structures and complicated velocity models.However,low-frequency,high-amplitude noises contaminate the signals in the image.Conventional imaging condition for RTM is comprised with the wavefields traveling upward and downward for source and receiver sides,respectively.The noise is more serious when there is a strong reflection interface in the velocity model to produce strong backscattering.The Laplasse filtering method will lose the low frequency information in the data,and make the frequency band move to the high frequency,which is not conducive to get the image of the steeply dipping structures and fracture structure.The traditional wavefield decomposition method can suppress the low-frequency noise,but it needs to be implemented in the frequency wavenumber domain,or it needs to solve the wave equation twice,it usually requires extremely heavy cost in computation in the 3D application due to Fourier transforms on both time and vertical axes.We proposed an effective wavefield decomposition method for reverse time migration using analytical wavefield in the time domain,which is computed by just solving the wave equation once.Our proposed method can improve the computation of wavefield separation.For time extrapolation,we are using the rapid expansion method to compute the wavefield and then compute the analytical wavefield,we can separate the wavefield into down-going and upgoing components for each time step in an implicit way.Taking the wavefields traveling opposite direction into account by decomposition for source and receiver sides,respectively,suppresses low wavenumber backscattered noise,We can bring the new imaging condition into practice.Applications to synthetic and real data sets demonstrate that the new imaging condition by an effective wavefield decomposition method for reverse time migration using analytical wavefield can effectively remove the undesired low-frequency noises which is common in

关 键 词：逆时偏移 偏移噪声 低频信息 波场分解 

分 类 号：P631[天文地球—地质矿产勘探]