Calculation of full-density Common Image Gathers (CIGs) in Reverse Time Migration (RTM) allows access to all the information acquired in wide azimuth towed streamer (WATS) seismic surveys on sub salt or other complex targets. The surface-offset RTM CIGs described in Giboli et al (2012) are relatively inexpensive to calculate and are exact analogues of standard Kirchhoff offset gathers. They can therefore be used in the same post-processing sequences that we have developed previously for Kirchhoff migrations, but allow application of similar flows to regions around and below salt and in other areas where Kirchhoff migration would be inadequate.
This paper presents a recent 3D depth imaging case history in which RTM gathers were calculated from WATS data, in the context of exploration and development in the Gulf of Guinea. We discuss the motivation for the use of RTM CIGs, the advanced pre-stack and post-stack workflow that was applied, and we demonstrate the improvement in the imaging results.
