Reverse Time Migration Using Vector Offset Output to Improve Subsalt Imaging – A Case Study at the Walker Ridge GOM

Technology advances, such as WAZ/FAZ acquisition, reverse time migration (RTM) and iterative salt imaging in model building, have greatly improved subsalt image quality. However subsalt imaging under complex salt overburden is still challenging. The fundamental issue lies with the imperfect illumination from limited acquisition. In the illumination shadow zones, the migration-generated artifacts and coherent noises, such as residual multiples and converted waves, become prevalent and can severely contaminate the images to cause interpretation difficulty. Migration vector offset output provides a domain in which the true imaging energy and noise can be separated as the imaging contributions focus in different vector offset tiles according to the subsurface structure orientation (azimuth and dip). Thus selective stacking the migration vector offset outputs based on the structural interpretation can achieve migration noise reduction and improve subsalt images.