追踪积分偏移法

Tra(?)ing integral migration,

传统的绕射积分偏移是以波动方程的克希霍夫积分解为基础,将散射信号以加权形式加到绕射曲线的顶点来完成的。由于它不能使界面完全归位,在水平方向上存在偏离现象,因此,必需使用成像射线追踪再进行一次深度偏移,才能将能量归位于散射点。实践表明,该方法在积分区间或偏移范围大的情况下会严重地降低剖面的信噪比。为此,我们基于该方法,提出一种沿法向进行射线追踪的追踪积分偏移法,这种方法通过两次射线追踪即可实现界面的完全归位。然后换算到垂直方向上进行时—深转换,所得深度剖面可克服成像射线追踪深度偏移有时出现空白区的缺陷。理论模型试算的结果表明,追踪积分偏移方法是切实可行的,并具有速度快、运算简单、信噪比高等优点,可为波动理论深度偏移提供准确的速度模型。

Conventionai diffraction integral migration, based on Kirchoff's integral of wave equation, is accomplished by putting scattered signals on the apex of diffraction hyperbola according to weighting coefficients. This migration method can not make a full migration to result in horizontal deviation; therefore, we have to use image ray tracing for an additional depth migration so as to focus energy on the scatter points. It is practically proved that this method reduces seriously signal-noise ratio of seismic section in the case of big migration aperture, or big limits of integration. On the basis of this diffraction integral migration method, we developed a normal ray-tracing integral migration method, which can achieve full migration of reflection interface after twice ray traings. Then time-depth conversion is made in vertical direction. The depth section produced in this way has no blank area, which sometimes results from image ray-tracing depth migration. The theoretical modeling result shows that the tracing integral migration method is feasible, has some advantages such as fast operation, high signal-noise ratio, etc., and provides accurate velocity model for wave theory depth migration.