不同介质模型的双聚焦计算方法

Double-focus algorithm of models in different medium.

双聚焦计算方法模拟了两个三维波场响应过程:一是三维波场正演过程;二是三维波场叠前偏移过程,因此双聚焦算法的关键在于波场外推。不同介质模型采用不同的波场外推方法:直接外推法适用于最简单的均匀介质模型;大步长逐层递推法适用于层状均匀介质模型;小步长三维网格递推法适用于复杂介质模型。实际应用表明:针对复杂地质目标的双聚焦成像空间分辨率和照明强度预测,对于优化三维观测系统设计和提高地震成像质量具有重要作用。考虑到三维正、反向波场递推的计算量极大,建议在多节点的并行机上进行复杂介质双聚焦方法的软件开发。

Double-focus algorithm simulates two processes of 3-D wavefield response: one is forward process of 3-D wavefield, the other is the process of prestack migration of 3-D wavefield, so that the key of double-focus algorithm is extrapolation of wavefield. Different extrapolation methods are used for the models in different media: the direct extrapolation is suitable for the model in the simplest homogeneous model; the recursive method layer by layer in large step is suitable for the model in layered homogeneous medium; the 3-D grid recursive method in small step is suitable for the model in complex medium. The practical application showed that the prediction of double-focus imaging spatial resolution and illuminating power for complex geologic targets plays an important role in optimum design of 3-D geometry and in improvement of seismic imaging quality. Considering a great mount of computational efforts in forward and inversive recursive computation of 3-D wave-field, we suggest that software development of double-focus algorithm in complex media should be carried out in parallel computer with multiple nodes.