基于双平方根方程的保幅地震偏移

Amplitude-preserved seismic migration based on double square root

本文提出了一种基于双平方根方程的保幅叠前深度偏移方法,首先从保幅的单平方根算子方程出发,将保幅的上、下行波场进行组合近似表示为全声波波场,然后推导出由双平方根算子定义的单程波方程;根据摄动理论把速度场分裂为层内常速背景和变速扰动,求得整个均匀层波场深度延拓的偏移时移量及振幅校正系数、各层的偏移时移量及振幅校正系数,得到最终的波场延拓值,实现了共炮域公式到CMP域公式的转换。理论模型试算和实际资料处理表明,该方法不但具有较高的计算效率和成像精度,而且可以输出正确反映地下反射系数的振幅信息,有利于AVO/AVA地震属性分析,提供精确的岩性识别与储层预测地震数据。

The paper presented a method of amplitude-preserved prestack depth migration based on double square root equation. Firstly, starting from the amplitude-preserved equation of single square root operator and combining the amplitude-preserved up-going wavefield with down-going wavefield to approximately represent full acoustic wavefield, then, deducing one-way wave equation defined by double squave root operator; according to perturbation theory, the velocity field is divided into constant velocity background in layer and velocity-changed disturbance to compute time-shifted values of migration and correction coefficients of amplitude for depth continuation of wavefield in whole uniform layer as well as in separate layers, obtaining final continuation value of wavefield and fulfilling the formula transformation from common-shot domain to CMP domain. It is shown by the tests of theoretical model and real data processing, the method not only has higher computational efficiency and imaging precision, but also can show the amplitude information reflecting underground reflection coefficients correctly, benefit to analyze the AVO/AVA seismic attributes, providing accurate seismic data for lithologic identification and reservoir prediction.