f Imaging subsalt structural targets by 3D pre-stack depth migration

We present a case history on delineating a subsalt structure in the Gulf of Mexico. Strong lateral velocity variations associated with a complex overburden which involves salt diapirism makes depth migration imperative to accurately image the subsalt structure. The complex overburden causes nonhyperbolic moveout of subsalt reflection events in CMP gathers. This makes CMP stack undesirable as input to depth migration, and requires the latter to be applied before stack. Moreover, the three-dimensional character of the boundary between the salt body and surrounding strata requires 3-D depth migration of 3-D seismic data.