Reciprocity and double plane-wave migration

Abstract

In plane-wave migration techniques, plane-wave data sets with seismic energy in both positive and negative ray-parameter sections are more desirable than those with seismic energy only in either positive or negative ray-parameter sections. Such plane-wave data sets are often referred to as optimal plane-wave data sets because they can be used to illuminate the subsurface from both sides of the targets and, therefore, can produce sharp images. Traditionally, to obtain optimal plane-wave data sets from one-sided gathers generated by marine seismic acquisition geometry, one needs to invoke the reciprocity principle to sort split-spread gathers prior to implementing plane-wave decomposition. We have investigated the applicability of the reciprocity principle in the double plane-wave (DPW) domain. We have developed an easy and efficient merging method that generates optimal plane-wave data sets in the DPW domain using one-sided shot gathers. We call this resultant plane-wave data set the “optimal DPW data set.” We find that an optimal DPW data set transformed from one-sided gathers is a good approximation to a DPW data set transformed from split-spread gathers with the same maximum offset as that of the one-sided gathers. We find that ray-parameter common-image gathers with continuous events in both positive and negative ray-parameter sections can be generated by migrating optimal DPW data sets. This helps migration velocity analysis and improves the subsurface illumination. In addition, we show that the computational cost of DPW migration methods could be reduced with the help of the reciprocity principle. We test our proposed method using a synthetic model to demonstrate its effectiveness.