起伏地表直接叠前时间偏移

Direct pre-stack time migration on rugged topography

针对起伏地表直接进行叠前时间偏移是目前复杂山地地震资料叠前成像处理的方向。如今研究的侧重点是通过参考面计算起伏地表条件下的地震波走时,进而进行叠前时间偏移,但是这一过程存在两个问题:其一是参考面选择不当会因高差和替换速度的不准确而带来走时计算误差;其二是地震数据经常规处理返回到采集地表面时可能破坏高频静校正效果。基于此,本文提出了以共成像孔径面为参考面且在共反射点道集上进行剩余时差校正的起伏地表叠前时间偏移的方法。文中分别应用简单模型、SEG起伏地表模型以及实际资料对该处理方法进行了测试,表明该方法是有效的。

Directly conducting pre-stack time migration on rugged tomography is the future direction for seismic data pre-stack imaging in complex mountain areas. The current key point is to calculate the travel time from the reference plane under the rugged topography condition, and then the pre-stack time migration is conducted. However two problems exist for the calculation, at first travel time calculation error can be caused by inaccurate elevation and replacement velocity which is actually resulted from wrong selection of reference plane, secondly high frequency static correction effect can be damaged by routine seismic data processing. In order to solve the problems the authors in this paper presented a new method in which common imaging aperture plane was taken as reference plane, then residual moveout correction was conducted on common reflection point gathers, and at last pre-stack time migration was carried out on rugged topography. The simple model, SEG rugged topography model and field data were respectively applied to test the new method, the testing results show that the new method is effective.