Kirchhoff弯曲射线叠前时间偏移及应用

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 CURVED-RAY PRESTACK TIME MIGRATION AND ITS APPLICATION

Kirchhoff prestack time migration based on ra y tracing is a high-frequency approximation method, and the velocity field need s to be smoothly processed while the ray tracing is used for calculating diffrac tion travel-time. In order to raise the accuracy of calculating 3-D travel-ti me in complex geologic media, to avoid a large number of calculation workloads a nd to reduce the cost of processing data, Kirchhoff curved ray prestack time mig ration has been developed and applied to real data processing in recent years. T his method synthesizes the advantages of both the quick speed of Kirchhoff prest ack time migration and the high imaging accuracy of Kirchhoff prestack depth mig ration, 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 pr inciple of Kirchhoff curved ray prestack time migration and the method of calcul ating 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 in dicated that not only the calculation efficiency can be guaranteed but also the migration homing under complex geologic conditions may be well realized by use o f the high-frequency approximation method.