Gravity modeling in the western Gulf of Mexico to support seismic imaging

Abstract

The western Gulf of Mexico is known to be a challenging area for seismic imaging because of the presence of complex salt structures. The salt in the GOM is located in two layers: shallower allochthonous canopies and diapirs and the deeper autochthonous layer. The latter layer — the mother salt — was deposited during the Late Jurassic period. As sediments continued filling the basin, most of that salt was mobilized upward, forming the allochthonous salt structures. The remnant salt in the autochthonous level may vary in thickness from zero to tens of thousands of feet in the salt roots and pedestals. The top of the shallower allochthonous salt (TOS) is usually mapped relatively confidently in seismic data, while interpretation for the base of the allochthonous salt (BOS) may be ambiguous and requires some guidance. The top of deeper autochthonous salt is usually somewhat uncertain in seismic data in the western GOM, and its base is rarely imaged in seismic at all. As rock salt has low density, the massive salt bodies create density contrasts with the surrounding sediments, which are the sources for anomalies in gravity fields. Thus, gravity data may be used as an independent tool to (1) test the existing salt model, (2) guide seismic BOS interpretation and/or (3) test different geological hypotheses (e.g., presence of salt roots, rafted sections, subsalt minibasins, etc.). This paper describes the utilization of the 3D gravity modeling in support of seismic imaging in the East Breaks and Alaminos Canyon protraction areas of the western Gulf of Mexico (Figure 1).