Kirchhoff弯曲射线叠前时间偏移及应用

KIRCHHOFF CURVED-RAY PRESTACK TIME MIGRATION AND ITS APPLICATION

基于射线追踪的Kirchhoff叠前时间偏移是一种高频近似方法,且利用射线追踪计算衍射走时需对速度场进行平滑处理。为了提高复杂介质中三维旅行时的计算精度,避开巨大的计算量,减少资料处理的成本,Kirchhoff弯曲射线叠前时间偏移近几年被提出来并逐步应用到实际资料处理中。该方法综合了Kirchhoff叠前时间偏移速度快、叠前深度偏移成像精度高的优点,利用层速度模型代替均方根速度模型来计算三维旅行时间。文章介绍了Kirchhoff弯曲射线叠前时间偏移的基本原理及利用层速度模型计算旅行时间的实现方法,并对四川某油气田资料进行了偏移成像。计算结果表明,Kirchhoff弯曲射线叠前时间偏移在保证计算效率基础上,较好地实现了复杂地质条件下资料的偏移归位。

Kirchhoff prestack time migration based on ray tracing is a high-frequency approximation method, and the velocity field needs to be smoothly processed while the ray tracing is used for calculating diffraction travel-time. In order to raise the accuracy of calculating 3-D travel-time in complex geologic media, to avoid a large number of calculation workloads and to reduce the cost of processing data, Kirchhoff curved ray prestack time migration has been developed and applied to real data processing in recent years. This method synthesizes the advantages of both the quick speed of Kirchhoff prestack time migration and the high imaging accuracy of Kirchhoff prestack depth migration, and the interval velocity model is used instead of the root mean square velocity model for calculating the 3-D travel-time in the method. The basic principle of Kirchhoff curved ray prestack time migration and the method of calculating the travel-time by applying the interval velocity model are introduced in the paper. By means of the migration imaging of one field in Sichuan, it was indicated that not only the calculation efficiency can be guaranteed but also the migration homing under complex geologic conditions may be well realized by use of the high-frequency approximation method.