共炮域波动方程叠前深度偏移技术在委内瑞拉探区的应用

Application of wave-equation prestack depth migration of common shot domain data in Venezuela exploration area

委内瑞拉探区为盐丘、剌穿、逆冲构造发育的复杂构造区,共炮域波动方程叠前深度偏移技术被认为是复杂构造区地震偏移成像的一个重要而有效的工具,该技术主要分为两步:第一步利用单程波波动方程,分别从炮点和检波点对波场进行向下延拓;第二步为成像调整,即在每一个成像点上,对延拓得到的连续的检波点和炮点波场进行相关处理。共炮域波动方程叠前深度偏移技术的不足之处是高频成分损失较多,造成剖面的相干性较强,偏移背景较差。本文分析了共炮域波动方程叠前深度偏移技术的参数试验及存在的问题,认为强相干背景、CPU计算能力、对地震资料的振幅补偿精度要求更高等因素影响该技术的推广使用。文中认为可在偏移耗时可以接受的条件下,尽可能地选择较大输入频率范围,能够改善偏移背景。实例分析表明,在构造复杂地区,叠前深度偏移成像效果要好于叠前时间偏移,共炮域波动方程叠前深度偏移成像效果要好于Kirchhoff叠前深度偏移。

The Venezuela exploration area is complex structural zone developed salt dome,diapir and o-verthrust structure, the wave-equation prestack depth migration of common shot domain data is considered as an important and effective tool for seismic migration imaging in complex structural area. The technique is mainly divided into two steps: the first step is to use wave equation of one-way wave for downward continuation of wavefield from shot and receiver points respectively; the second step is imaging adjustment,that is,at each imaging point, the relevant processing is implemented for continuous wavefield at receiver and shot points obtained from the continuation. The shortcoming of wave-equation prestack depth migration of common shot domain data is more losses of high-frequency components that make the section strong cohenrence and poor migration background. The paper analyzed the parameters tests and existed issues of wave-equation prestack depth migration of common shot domain data,and considered that the factors such as strong coherent background, CPU computational capacity, higher demand on amplitude compensation precision of seismic data have influence on popularization of the technique. The paper considered that in a receivable migration time-consuming condition, the migration background could be improved by doing our effort to select the higher input frequency rage. The cases showed that in structure-complex area, the imaging effects of prestack migration is better than that of prestack time migration and wave-equation prestack depth migration of common shot domain data is better than the Kirchhoff prestack depth migration.