基于特征能量梯度算子的时间域全波形反演  

Time domain full waveform inversion based on eigen energy gradient equation

作　　者：张文祥 吴国忱[1] 王玉梅[2] 

机构地区：[1]中国石油大学(华东)地球科学与技术学院,青岛266580 [2]中国石化胜利油田物探研究院,东营257000

出　　处：《地球物理学进展》2015年第1期363-371,共9页Progress in Geophysics

基　　金：国家重点基础研究发展计划(2013CB228604)资助

摘　　要：全波形反演中构建常规梯度算子过程中需要三步骤:震源子波的正向传波场传播,波场残差的反传波场和波场互相关构建梯度算子,其过程存在数据量大、效率低等缺点,为提高反演的效率,本文针对常规时间域梯度算子进行优化,提出了基于特征能量的梯度算法.在正传过程中计算每一个网格点上的正传波场的最大激发能量及其对应的时间步,保存一个子波时间长度的利用特征能量以构建梯度算子.在构建梯度算法中利用保存的子波长度的特征能量进行构建梯度算子.该算法无需保存震源的正传波场,可以减少运算过程中的磁盘读写,提高全波形反演的计算效率.在Mamousi模型梯度测试和实际资料的反演测试中表明:该算法在可以保证梯度算子的精度,具有数据读写量小的优点,效率高的优点.The time-domain full waveform inversion is a nonlinear inverse problem,which is needed to compute the gradient of the error function.The adjoint-state method for computing gradient needs three main steps：a forward propagation of wavefied using actual wavelet,backward propagation of wavefield residual and correlation between these two wavefields at each space point.The adjoint-state method for gradient of FWI needs very large disk storage and vast amounts data input/output operation.We present a new method for the time-domain FWI＇ s gradient to improve the efficiency and the new algorithm is named the excitation main energy gradient equation.In the process of forward propagation,it calculates the maximum amplitude and corresponding occurrence time step.And then it calculates a wavelet length of time windows at each grid point to save the wavefiled.Through the time window,the new schemes extract the eign energy of each grid points and the energy in the time windows called the eign energy and time step length of wavefiled reduced a length of wavelet.Using eign energy to compute the gradient need no more to save all snapshot and it improve the disk storage and it decrease the mount of I/O operation.In this paper we apply the new method to invert theoretical model and actual data.Compared with the conventional equation,the excitation main energy gradient equation can remain same accuracy,shorten I/O time and improve the efficiency of inversion.

关 键 词：全波形反演 梯度算子 特征能量 正传波场 

分 类 号：P631[天文地球—地质矿产勘探]