3D Pre-Stack Depth Migration: Velocity Sensitivity and its Effects on Reservoir Definition

3-D pre-stack depth migration is a viable imaging process when implemented on parallel super-computers. Run times for complete output volumes that would have been years on conventional computers are now on the order of weeks. An iteration on the important velocity model, however, can be done with a small subset of the output volume and hence can be accomplished in a few days. Sub-salt imaging is a particularly difficult imaging problem that requires 3-D pre-stack depth migration. A 3-D sub-salt case history from the Gulf of Mexico illustrates the benefits of and effort behind 3-D prestack depth migration and migration-velocity analysis and underscores the perils of 2-D pre-stack depth migration in imaging complex structure.