速度扫描法共聚焦点道集偏移速度分析

Migration Velocity Analysis of Common Focus Point Gathers Based on Velocity Scanning

共聚焦点(CFP)偏移是基于等时原理,通过激发聚焦和检波聚焦的双聚焦实现叠前深度偏移的地震成像方法.在速度模型正确的情况下,聚焦点响应和它的逆时聚焦算子的聚焦度差异时差(DTS)等于零.此时,二者的相关能量最大.若速度不正确,则差异时差不为零,相关能量弱,但根据差异时差,可以进行算子的更新.基于差异时差分析、速度扫描和相关能量准则,实现了正确算子的求取和偏移速度的估算.模型试算和实际资料试处理表明了所用方法的正确性和有效性.

Common focus point（CFP） migration based on the equal travel-time principle is a kind of pre-stack depth migration method through focusing in both emission and detection. That is, to correct macro velocity model, differential time shift （DTS）is zero between the focus-point response and its time-inverse focus operator. Correlative energy between the operators and focus point responses is maximal. If the velocity is not correct, DTS is not zero any more and the correlative energy is small. But, according to DTS, we could update the erroneous operators. Through velocity scanning and maximum energy criterion, the optimal velocity corresponding to correct focusing operator could be obtained based on updated operators. In this way, the whole velocity could be modified and updated. Model tests and processing of real seismic data show the correctness and validity of our method.