加权平面波叠前深度偏移

Weighted plane wave prestack depth migration.

常规平面波偏移具有计算效率高的特点,但是它的偏移精度却受慢度取值范围的影响:慢度范围太小,在断层位置处,平面波偏移会产生平滑作用,偏移效果不明显;慢度范围较大,在断层位置和浅层地层中,平面波偏移会产生低频化人工混淆。为了克服常规平面波偏移的这些缺点,提出了加权平面波偏移。它根据不同慢度取值范围对偏移结果的不同影响,在常规共平面波道集偏移结果上进行加权叠加,即对常规平面波偏移结果进行“带通”滤波。Marmousi模型的数值试验分析表明,加权平面波偏移方法偏移计算速度与常规平面波偏移基本相同,并能保证构造偏移效果的稳定性,提高叠前深度平面波偏移方法的偏移效果。

Plane wave migration has an advantage of high computational efficiency. Its migration precision, however, depends on the range of slowness. Plane wave migration will smear images along fault if the range of slowness is too small, or will generate aliasing along fault and in the shallow if the range of slowness is too large. To cope with these problems, we proposed a method called weighted plane wave migration. This method performs weighted summation over conventional coplanar wave gathers, which is equivalent to perform bandpass filtering on conventional plane wave migration. Numerical experiments on Marmousi model showed that the weighted plane wave migration and conventional plane wave migration are matched in computational efficiency, whereas the weighted plane wave migration ensures the image quality of structures.