起伏地表条件下基于复Pade逼近的叠前深度偏移

Prestack depth migration using complex Pade approximations for irregular surfaces

叠前深度偏移是解决复杂地表和复杂构造地震成像的有效技术,而波场"直接下延"法实现了复杂地表条件下的地震成像.基于上述成果,结合高精度的波场延拓算子,本文提出了一种新的叠前深度偏移方法,这种方法是在波场延拓时,对声波方程中的平方根项进行复Pade逼近,通过推导得到基于复Pade逼近的傅里叶有限差分算子,结合波场"直接下延"法,实现了起伏地表条件下的叠前深度偏移,该算法减少了偏移噪音,从而得到准确、稳定的偏移成像结果.通过理论模型试算和实际资料试处理,验证了该方法的有效性.

Oil and gas exploration is turning to the areas with irregular topography and complex geologic structures.Prestack depth migration is a valid way to deal with irregular topography and complex geologic structures.＂Wave field downward continuation＂ based on accumulating step by step is a valid way to solve the problem of irregular surface migration.Based on these achievements,this paper shows a new prestack depth migration method combined with high-precision wave field continuation operator.A complex Pade approximation of the square root of the acoustic wave equation is used for wavefield extrapolation.We derive the Fourier finite difference operator based on complex Pade approximation.Based on this operator,we use the method of ＂wave field downward continuation＂ to achieve the prestack depth migration of irregular topography.It produces images with fewer noises and yields accurate and stable imaging results.Tests on the Marmousi model data set and the real seismic data show that the superiority of the proposed migration method.Compared to other migration methods,this method has better migration quality.