In deep water Gulf of Mexico (GOM), defining accurate salt geometry is essential for imaging geological structures beneath complex salt bodies. Reverse time migration (RTM) handles complex wave propagations in any direction without dip limitation, and is now the standard imaging algorithm in salt model building. With increasing computing capacity and integrated imaging and interpretation, our ability to use RTM imaging as an interactive tool for delineating salt geometry has been significantly improved. The conventional RTM salt model building is a top-down approach which consists of various steps of migration and interpretation: sediment flood RTM and picking the Top of Salt (TOS), salt flood RTM and picking the Base of Salt (BOS), and overhang RTM and interpretation as needed. However, in the areas with complex salt geometry, such as narrow mini-basin with surrounding salt bodies, the conventional top-down salt building approach may not be conducive to correct salt body interpretation and can lead to poor images beneath the salt. In this paper, we demonstrate the application of RTMbased prismatic wave imaging in complex salt model building, in particular the introduction of dual flood RTM to evaluate the prism waves and correctly interpret the salt horizon. A 2D synthetic case study is utilized to demonstrate the prismatic wave work flow. The technique is then applied to a marine wide azimuth dataset in Walker Ridge, Gulf of Mexico, in order to improve subsalt imaging in the complex structural setting.

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