Velocity Model Building Using Pre-Stack Depth Migration

Abstract

Time migration algorithms prove to be inadequate when trying to correctly image seismic sections in areas of complex geology. In such media, velocities vary both vertically and laterally giving rise to non-hyperbolicity in the observed moveout of the seismic reflections. To deal with this situation, a depth migration must be employed. However, a dilemma arises in that the performance of the pre-stack depth migration is sensitive to errors in the velocity model supplied by the user, that is the more accurate the underlying velocity model, the better the migrated image. This sensitivity provides an excellent tool for the iterative building of depth models (Figures 1 & 2). We present a method that combines pre-stack depth migration with velocity analysis and mapmigration.