VSP上下行反射波联合成像方法研究

VSP资料上下行波场发育丰富.本文在分析VSP直达波、上行反射波、下行反射波传播路径及其照明范围的基础上,指出了常规VSP波动方程偏移方法缺陷,进而通过修改波场延拓方式,提出了上下行反射波联合成像方法,并在高频近似下分析了该方法的成像原理.该方法不需要进行VSP上下行反射波场分离,能够同时对VSP资料中的一次反射波、自由表面多次波、层间多次波进行成像,比常规成像剖面具有更宽的成像范围和更好的成像效果.该方法能够对下行一次反射波进行成像,从而可以实现常规偏移方法难以处理的高陡倾角构造成像.模拟资料和实际资料处理证明了本文方法的正确性.

Joint imaging method of VSP upgoing and downgoing reflection wave

Upgoing and downgoing waves are rich in VSP data. Based on the analysis of propagation paths and illumination ranges of VSP direct, upgoing, and downgoing reflection wavefields, we pointed out the defects of the conventional VSP wave equation migration method, and then proposed a joint imaging method of upgoing and downgoing waves by modifying wavefield continuation pattern. Under high-frequency approximation, we analyzed the imaging principle. This method can simultaneously image VSP primaries, free surface multiples, and interbed multiples without the needs of separating upgoing and downgoing waves. It has wider imaging range and better imaging results than the conventional imaging profiles. Moreover, this method is able to image downgoing primaries, thus it can image steep dip structures which can't be imaged by the traditional method. Processes of simulated and real field data proved the correctness of this method.