苏北大陆科学钻探靶区深反射地震的叠前深度偏移

PRESTACK DEPTR MIGRATION OF DEEP SEISMIC REFLECTION DATA AT THE CONTINENTAL SCIENTIFIC DRILLING SITE IN SULU

由于深反射地震数据具有信噪比低和记录长度长等特点，叠前深度偏移方法的应用有许多困难．为此，我们研究了一种适合于深反射地震的叠前深度偏移方法；包括：用逆风有限差分方法计算程函方程；在常规速度扫描的基础上，用协方差控制提高速度分析精度；用联合反演算法计算层速度，再插值后得到初始速度模型；用Ｋｉｒｃｈｈｏｆｆ法作为偏移速度分析工具，求得最终的速度模型；最终的速度模型作为有限差分深度偏移的输入，求得最终的偏移结果．用该方法对“中国大陆科学深钻工程”东海二维深反射地震数据ＤＨ－４线进行了叠前深度偏移，取得了良好的效果。

Due to the low signal-to-noise ratio and long recording length of deep seismic data, the application of prestack depth migration has some difficulties. We developed a depth migration method for deep seismic data processing as follows. The upwind finite-difference method is used for traveltime calculations; a high resolution velocity analysis by co-variance analysis, a joint inversion method for internal velocity, and a Kirchhoff prestack depth migration scheme are sequentially used for the velocity analysis on semblance gathers; and finally the finite-difference reverse time migration is employed for final imaging. We used our prestack depth migration scheme to process 2D deep seismic reflection data in Donghai for site selection of Chinese Continental Scientific Drilling Program. The resulting migrated profile has higher resolution and is more informative than those obtained by conventional migration processing.