Reverse VSP prestack depth migration with multiples

Abstract

Summary Reverse VSP (RVSP) can lead to good subsurface images, although the corresponding data processing is quite challenging due to the presence of strong down-going waves and multiples. We have modified a pseudospectral prestack depth migration (Hou and Zhou, 1999a,b) for the case of RVSP. This method uses a numerical solution of full wave equation to propagate forward wavefield from each source and backward wavefield from each receiver. The depth imaging of RVSP is achieved by one step, without the often tedious preprocessing of multiple attenuation and separation of up-going and down-going waves. We use synthetic reflection gathers and RVSP data to test the concepts and algorithm. Prestack depth migration of synthetic reflection data shows that internal multiples can make significant contribution to depth imaging. The synthetic RVSP image verified that the multiples (and down-going waves) can be used for imaging, including the subsurface structures above the source location. As a field data test, a RVSP data set from Michigan shows that the up-going and down-going waves can not be separated in a reliable fashion due to a narrow range of source depths. Nevertheless, the depth imaging using the full wave method reveals the structures above the sources.