逆时偏移中用Poynting矢量高效地提取角道集

Extracting efficiently angle gathers using Poynting vector during reverse time migration

逆时偏移在提高复杂介质的成像质量方面表现出了优越的性能,但逆时偏移对速度精度的要求比较高.共成像点道集是一种非常重要的叠前深度偏移输出,它除了能为深度偏移处理提供速度信息外,还能够提供振幅和相位等信息,为后续的属性解释提供依据.本文提出一种在逆时偏移成像过程中提取角度域共成像点道集的方法,该方法采用矢量波动方程进行波场传播,并用能流密度矢量(Poynting vector)计算反射角,最后应用互相关成像条件输出角度域共成像点道集.该方法简单易于实现,且几乎不需要额外的计算量和存储量,非常适合于进行逆时偏移速度分析,同时提出的角道集也能用于进行AVA等分析.最后通过模型算例和实际数据检验了方法的有效性和优越性.

Reverse time migration has shown its superior performance for imaging the complex subsurface structures, but it needs a more accurate velocity model. Common-image gathers are an important output of prestack depth migration. They not only can provide velocity model for depth migration, but also can provide amplitude and phase information for subsequent subsurface attribute interpretation. In this paper, we have developed a method for extracting angle domain common-image gathers during reverse time migration. In our method, vector wave equation is used to calculate the wavefield, energy flux density vector （Poynting vector） is used to calculate the reflection angle, and finally cross-correlation imaging condition is used to obtain the angle domain common-image gathers. Finally, a model and a field marine data are done to show the effectiveness and advantages of this new method.