基于共聚焦的三维最大能量积分法叠前深度偏移
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摘要
本文从WRW模型理论出发,提出了基于共聚焦成像理论的最大能量积分法成像技术,其原理为:分别假设地下某深度点存在一个虚拟接收点和一个虚拟理想震源,通过对数据矩阵进行时移后加权叠加的方法,实现针对该深度点的上行波场反向延拓的检波聚焦,通过对CFP道集进行时移后加权叠加的方法,实现针对该深度点的下行波场反向延拓的震源聚焦,生成该网格点成像结果,最后可提取t=0时刻的成像波场。其核心技术在于对聚焦算子(格林函数)的计算。本文基于单程波动方程,在地震波的有效频带范围内计算携带最大能量的三维聚焦算子,在此基础上完成基于共聚焦成像理论的最大能量积分法深度成像。文中方法成像精度接近波动方程方法,同时又具有常规积分方法适应野外观测系统、计算效率高的优点,因此是一种兼具精度和效率的实用方法。
Starting from WRW model theory,the paper proposed max-energy integration imaging technique based on common focus imaging theory, which supposes there exist a virtual receiver point and a virtual source point at a certain underground depth point.The receiver focus of backwards continuation of upgoing wavefield at that depth point can be fulfilled by using data matrix to carry out post-time-shift weighted stack, The source focus of backwards continuation of downgoing wavefield at that depth point can be fulfilled by using CFP gathers to carry out post-time-shift weighted stack,producing the imaging results at that grid point,and finally the imaging wavefield at t=0 can be detected.The kernel technique lies in computation of focus operator (Green function).Based on one-way wave equation, the paper computes the 3-D focus operator with maximum energy within useful band scope of seismic waves,and finishes max-energy integration depth imaging based on common focus imaging theory.The imaging precision of the approach presented by the paper closes to that of wave equation approach, and the approach has same characters of suitable to field geometry and high computational efficiency as common integration method has, and is practical approach with both precision and efficiency.
Starting from WRW model theory,the paper proposed max-energy integration imaging technique based on common focus imaging theory, which supposes there exist a virtual receiver point and a virtual source point at a certain underground depth point.The receiver focus of backwards continuation of upgoing wavefield at that depth point can be fulfilled by using data matrix to carry out post-time-shift weighted stack, The source focus of backwards continuation of downgoing wavefield at that depth point can be fulfilled by using CFP gathers to carry out post-time-shift weighted stack,producing the imaging results at that grid point,and finally the imaging wavefield at t=0 can be detected.The kernel technique lies in computation of focus operator (Green function).Based on one-way wave equation, the paper computes the 3-D focus operator with maximum energy within useful band scope of seismic waves,and finishes max-energy integration depth imaging based on common focus imaging theory.The imaging precision of the approach presented by the paper closes to that of wave equation approach, and the approach has same characters of suitable to field geometry and high computational efficiency as common integration method has, and is practical approach with both precision and efficiency.
引文
[1]Berkhout A J.Pushing the li mits of seismic i maging,part I:Prestack migration in terms of double dynamic focusing.Geophysics,1997,62:937~953
[2]Nichols D E.Imaging complex structures using band li mited green functions.Ph Dthesis,Stanford Univer-sity,1994
[3]李振春等.基于共聚焦点道集的叠前深度偏移及其应用.石油大学学报(自然科学版),2003,27(4):27~31
[4]匡斌等.任意复杂介质中主能量法地震波走时计算.地球物理学报,2005,48(2):390~394
[2]Nichols D E.Imaging complex structures using band li mited green functions.Ph Dthesis,Stanford Univer-sity,1994
[3]李振春等.基于共聚焦点道集的叠前深度偏移及其应用.石油大学学报(自然科学版),2003,27(4):27~31
[4]匡斌等.任意复杂介质中主能量法地震波走时计算.地球物理学报,2005,48(2):390~394
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