Understanding the tectonic history offshore Southern Gabon with high resolution seismic, gravity and magnetics

Abstract

Having produced oil since 1957, Gabon has several proven petroleum systems, both onshore and offshore. Over the last decade interest has moved towards the deep offshore area where a number of early exploration wells have been successful in finding hydrocarbons, but also highlighted the need to answer questions about trap formation, source maturation and timing of charge in this new area. Following this exploration trend, and aiming to answer these key questions, a recent 3D broadband seismic survey was acquired in conjunction with shipborne gravity and magnetic data in the southern deep offshore area of Gabon. Understanding the tectonic evolution of the basin and its impact on the petroleum systems, requires the integration of seismic with the concurrently acquired gravity and magnetic data. Potential fields data provide deep crustal information where it may be challenging for seismic to resolve deep geological features, and vice versa for the shallower sedimentary section. One of the key objectives of the potential fields study was to model crustal types and thicknesses for input into basin modelling. Upper and lower crust ratios, as well as the crustal characteristics and processes in the continental-oceanic transition zones, are important for understanding the temperature regimes undergone by potential source and reservoir rocks. Knowing the distribution of lower- or higher-density crust, and zones of higher susceptibility, provides insight into the characteristics and timing of formation/deformation of the crust along the margin.