South Atlantic Rifting and the Impact on Equatorial Atlantic Deepwater Exploration

Abstract

Abstract

The Equatorial Atlantic is a volcanic margin with a very different petroleum system to the widely explored Santos, Campos, Espirito Santo, and Kwanza, Central South Atlantic basins. Unlike these basins which are magma poor margins, the Equatorial Atlantic never developed the sag phase lacustrine source rocks found in Central South Atlantic basins. Brazilian sag phase, Lagoa Feia, charges both the Pre-Salt and Post Salt reservoirs. Whereas in West Africa, the Pre-Salt is charged by a sag phase source, and the Post-Salt is charged by marine source rocks.

The West Africa Post Salt petroleum system shares similarities with the Equatorial margin in that; deepwater and restricted marine sequences act as source rocks. The Equatorial margin experienced magma enhanced active rifting which resulted in narrow continental rifted margins without a thermal sag phase. These narrow margins, limit the extent marine source can be matured on continental crust. Early to Late Albian transcurrent Equatorial margin separation also produced a restricted seaway which resulted in high TOC marine source rocks. Both the Early Aptian and Albian sources have been largely overlooked as potential sources for hydrocarbon charge. The narrow seaway between Africa and Brazil produced Early Albian hyper-saline and later Albian restricted marine sources. Where these sequences occur on oceanic crust, the additional burial and greater time for maturation suggests these intervals may result in viable charge for both non-marine and deepwater marine reservoirs.

AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016