Subsurface Structure in Southeastern Gulf of Mexico From Integrative Geophysical Analysis

Abstract

Subsurface structures in the southeastern Gulf of Mexico are challenging to map due to the presence of complex salt bodies, particularly with respect to the pre-salt sedimentary section. In order to better understand the subsurface geology of this area, we have created three cross sectional models based on published seismic lines. We combined gravity, magnetic field, seismic reflection profiles, a few seismic refraction data points, and well logs from public domain sources. The major goal of this project was to develop subsurface models based on a multitude of geophysical methods.

We applied several filters to gravity and magnetic grids to highlight the Ocean-Continent crustal Boundary (OCB). We developed three 2D subsurface models along seismic reflection profiles, and used them to validate our OCB interpretation. These models consist of sedimentary layers constrained by seismic data, upper and lower continental crust, oceanic crust, and the upper mantle. We assigned physical properties (densities and magnetic susceptibilities) based on well data and typical values for certain rock types according to published literature. We constrained densities and magnetic susceptibilities in corresponding layers to be consistent across all three models. These models allowed us to evaluate the thickness and spatial extent of the pre-salt sedimentary section, as well as the thicknesses of various crustal units.

As a result of this project we were able to map the OCB location in the Southeastern Gulf of Mexico, evaluate the thickness and delineate an extent of the pre-salt section, and derive the thickness of individual crustal units. By combining several independent geophysical methods, we developed more confident subsurface models.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018