双复杂条件下带误差补偿的频率空间域有限差分法叠前深度偏移

Xwfd pre-stack depth migration based on dual-complexity with error compensation correction

油气勘探的重点正转向复杂地表条件和复杂地质条件的区域.双复杂条件下的叠前深度偏移方法是解决复杂地表条件和复杂地质构造成像的有效手段,基于"逐步累加"的"直接下延"法和"波场上延"法都是解决复杂地表成像的有效手段.波动方程的频率空间域有限差分深度偏移对介质速度横向变化有较强的适应性,适宜于复杂构造的偏移成像.然而,频率-空间域有限差分法求解时引入的误差影响了成像的质量,我们用了带误差补偿的频率-空间域有限差分偏移改善了起伏地表条件下的频空域有限差分偏移质量,对模型和实际资料进行了试算,得到了较好的成像效果.误差补偿可以在若干个外推步长上进行,通过对比分析,我们发现,相对于基于起伏地表的傅立叶有限差分法偏移来说,该方法在改善起伏地表条件下偏移成像质量的同时,也具有较高的运算效率.

Oil and gas exploration is turning to the areas with irregular topography and complex geologic structures. Prestack depth turns out to be a valid way to deal with irregular topography and complex geologic structures. ＂wave field downward continuation＂ and ＂wave field upward continuation＂ are valid way to solve the problem of irregular surface migration, xwfd pre-stack migration based on wave equation has strong adaptability to the medium which has strong variable transverse velocity and it can be used for migration with dual-complexity. However the error arise from xwfd equation affect the quality of dual-complexity migration. We use the xwfd prestack migration with error compensation to improve the migration quality of dual-complexity. Numerical tests in theoretical model and actual data have been done and get better result. The error compensation can be done among several steps. We can find from the analysis that comparing to the ffd depth migration based on irregular surface, it has both advantages in migration quality and efficiency.