叠前深度偏移技术在东海地区的应用

A Prestack Depth Migration Example in the East China Sea

叠前深度偏移是目前理论最先进、精度最高的地震波成像技术,它主要包括Kirchhoff积分法和波场外推法(也称波动方程法)。文章首先简要介绍了Kirchhoff叠前深度偏移的基本原理。然后从初始速度模型建立、粗网格叠前深度偏移与共成像点道集输出、基于共成像点道集的偏移速度分析与速度模型更新、最终精细成像处理等方面,详细讨论了Kirchhoff叠前深度偏移处理的实现流程。接着介绍了该技术对东海钱塘凹陷二维和西湖凹陷三维地震资料的成像效果,以及相对于叠前时间偏移在构造成像精度与振幅保持方面的优势。最后探讨了与该项技术实际应用有关的其他一些问题。

Prestack depth migration is by now one of the most advanced and accurate seismic imaging technology, which mainly includes Kirchhoff integral method and wave-field continuation method （wave equation method）. First we describe the principle of Kirchhoff prestack depth migration. Then the detailed procedure of application is discussed： initial velocity model creation, output of common imaging gather with large grid, migration velocity analysis and velocity model updating, and final prestack depth migration. A case study on 2-D and 3-D seismic data is played in the East China Sea and the imaging results are compared with that of prestack time migration. Finally we discuss some issues for the application of prestack depth migration.