稳定的保幅高阶广义屏地震偏移成像方法研究

The method of preserved-amplitude seismic migration imaging with stable generalized high order screen

以先进的波动理论为基础的波动方程保幅地震偏移成像是在给出正确位置的同时也给出真实振幅的一种特殊完善.作者从保幅单程波动方程的非稳态相移公式出发,基于反问题求解中常用的摄动理论,利用单平方根算子的渐进展开,从而推导出保幅叠前深度偏移方程的高阶广义屏形式;针对散射波场计算项对于横向变速介质的不稳定性,通过数学近似提出一个有效提高稳定性的策略,应用到波场递归外推过程中,从而得到一种稳定的保幅高阶广义屏叠前深度偏移算子.理论模型试算和实际资料处理表明,该方法不但可以更精确地使散射能量聚焦、归位,提高成像精度;而且可以输出正确反映地下反射系数的振幅信息,使AVO响应更加清晰,提高了AVO资料的分析精度.

Wave equation preserved-amplitude seismic migration imaging has a special function that can give true amplitudes as well as the correct locations based on advanced wave theories. The author first starts from the unstable phase shift expression of preserved-amplitude one way wave equation. Based on perturbation theory which is often used in reversed question solution, the author uses the progressive expansion of single square root operator to drive a high-order generalized screen form of preserved-amplitude prestack depth migration equation. To solve the unstable problem in lateral variable speed media caused by computation items of the scattering wavefield, the author proposes a strategy which can effectively improve the stability by math approximation. Then this strategy is applied to the wavefield recursion extrapolation, so a kind of stable preserved-amplitude prestack depth migration operators of high-order generalized screen are obtained. Theoretical model testing and real data processing indicate that this method can not only make scattering energy be focused and migrated to the correct position to improve imagingaccuracy but also output the amplitude information which reflects coefficients. So this method has clearer AVO response and can AVO data. the correct subsurface reflection enhance analytic precision for