几种叠前逆时偏移成像条件的比较

Imaging condition comparison of prestack reverse-time migration

叠前逆时偏移常用的成像条件主要有初至时成像条件、最大振幅到达时成像条件和互相关成像条件。初至时成像条件以成像网格点初至波的到达时间作为成像时间,计算速度快,适用于介质相对简单的情况。最大振幅到达时成像条件以成像网格点出现最大入射振幅的时间作为成像时间,选取能量最强的绕射波聚焦成像,提高了成像质量。互相关成像条件利用的是入射波和反射波的互相关,偏移前需要模拟整个放炮过程,计算量和存储量都很大,但能够充分利用全波场信息,可使各成像网格点多次成像,从而有效压制成像噪声。Marmousi模型叠前逆时偏移成像结果表明,互相关成像条件的抗噪性能优于初至时成像条件和最大振幅到达时成像条件,当偏移速度场足够准确时,互相关成像条件可以实现多次波成像。

The first arrival imaging condition,maximum amplitude imaging condition and cross-correlation imaging condition are three main imaging conditions used in prestack reverse-time migration.The arrival time of the incident waves in the grid were used by both the first arrival imaging condition and the maximum amplitude imaging condition.The first arrival imaging condition considers the first arrival time obtained by ray tracing or eikonal equation as imaging time,and is suitable for simple medium.However,the maximum amplitude imaging condition considers the time at which maximum amplitude appeared as imaging time,and has improved imaging quality.The cross-correlation imaging condition uses the cross-correlation between incident waves and reflected waves.However this condition needs to simulate field recording of wave propagation before migration.Imaging condition computation and data storage are huge.The advantage of cross-correlation imaging condition is that it can image repeatedly.Marmousi model examples demonstrates that the cross-correlation imaging condition has good multiple imaging and better denoising performance than the first arrival time imaging condition and the maximum amplitude imaging condition.