逆时偏移中的归一化加权互相关成像条件及应用

成像条件是决定声波方程叠前逆时深度偏移效果的重要因素。常规的归一化互相关成像条件能补偿深部地层的反射波能量,但无法压制地震波逆时偏移过程中产生的偏移噪声。针对归一化互相关成像条件的主要缺陷,从二维声波方程出发,在交错网格空间中推导了声波方程逆时延拓的高阶有限差分格式和PML吸收边界条件,进而在对常规互相关成像条件分析的基础上对其进行改进,给出了一种加权互相关成像条件,即在成像过程中利用炮检波场的夹角进行加权校正,以实现只利用炮点下行波场与接收点上行波场进行成像的目标。模型数据和实测资料偏移结果表明,归一化加权互相关成像条件成像效果明显优于常规归一化互相关成像条件。

Normalized Weighted Mutual Correlation Imaging Condition in Reverse Time Migration and Its Application

The imaging condition is an important factor to determine acoustic wave equation prestack reverse time depth migration effec- tiveness. The conventional normalized mutual correlation imaging condition can compensate deep strata reflected energy, but can not suppress noises from seismic wave reverse time migration. In allusion to main defect in normalized mutual correlation imaging condi- tion, starting from 2D acoustic wave equation, deduced the equation＇ s reverse time extrapolation high order finite difference scheme and PML absorbing side boundm7 condition in staggered grid, then carried out improving based on conventional mutual correlation im- aging condition analysis. A kind of weighted mutual correlation imaging condition puts out, that is using shot-detector wave fields in- cluded angle to carry out weighted correction, realize imaging use only shot point downward wave field and receiver site upward wave field. The model data and measured data migration has shown that the normalized weighted mutual con-elation imaging condition is ob- viously superior to conventional normalized mutual correlation imaging condition.