最小二乘叠前时间偏移在川东南复杂构造成像中的应用

Application of least-squares migrationin imaging of complex structures in Southeast Sichuan

地震偏移成像本质上是地下反射系数经过Hessian算子滤波后的模糊化结果,成像分辨率和振幅保真度较低。为了消除Hessian算子的影响,将地震成像看作最小二乘意义下的反演问题,通过引入一对互为共轭关系的叠前时间偏移/反偏移算子,采用共轭梯度法迭代求取与地震数据相匹配的反射系数最优解。理论模型和实际资料处理表明,最小二乘叠前时间偏移(LS-PSTM)能够压制偏移噪声并提高成像分辨率和振幅保真度,有利于改善川东南地区茅口组岩溶缝洞体、高陡构造以及断裂成像质量。

Seismic migration imaging is essentially the fuzzy result of underground reflection coefficient filtered by Hessian operator,and the imaging resolution and amplitude fidelity are low.In order to eliminate the influence of the Hessian operator,the seismic imaging is regarded as an inversion problem in the sense of least squares,by introducing a pair of pre-stack time migration/demigration operators that are conjugate relations with each other,the conjugate gradient method is used to iteratively obtain the optimal solution of the reflection coefficient matching the seismic data.The theoretical model and actual data processing show that the least squares pre-stack time migration(LS-PSTM)can suppress the migration noise and improve the imaging resolution and amplitude fidelity,which is beneficial to improve the imaging quality of karst fractures and caves,high-steep structures,and faults in the Maokou Formation in southeastern Sichuan.