Analogies in the Salt Tectonics Styles and Petroleum Exploration between the Brazilian and West African Margins

Salt tectonics is responsible for the majority of hydrocarbon plays in the Brazilian and West African margins, particularly for the post-salt plays related to Albian carbonates and Cretaceous turbidite reservoirs. Nonetheless, several sedimentary basins in the South Atlantic are characterized by important hydrocarbon discoveries even in areas where evaporites are not present, such as the Niger Delta and the Equatorial Transform Margin in West Africa, north of the Aptian salt basin. South of the Walvis Ridge in West Africa there are a number of discoveries in Namibia and South Africa, which are considered frontier regions for petroleum exploration in deep waters.

This presentation will focus on the South Atlantic conjugate margins where Aptian salt is observed in exploratory boreholes or indicated by seismic interpretation.

Important differences exist in the distribution of the evaporites in conjugate sedimentary basins along these margins. The Santos Basin is characterized by the largest evaporite basin in the South Atlantic, with a major antithetic fault controlling the occurrence of the

Cabo Frio Albian gap, and the southern margin is characterized by an indentation of the salt basin associated with an aborted oceanic ridge that penetrated the salt basin but was aborted by Late Aptian/Early Albian times. The conjugate Benguela Basin is

characterized by a narrow strip of rift and salt basin, and its tectonic development is probably related to a transform margin setting.

The salt basin between the Campos and the Kwanza basins is more symmetric between the two sides of the margins, and both margins are characterized by allochthonous salt advancing basinwards towards the oceanic crust.

The northern Espirito Santo Basin is characterized by a major volcanic province (Abrolhos Volcanic Complex) emplaced in the basin by Late Cretaceous / Early Tertiary time. It is associated with reverse faults and also with allochthonous salt structures in the deep water region, which constitute a new exploratory play for the Brazilian margin. The African margin at this conjugate segment is characterized by a much wider salt basin which extends from Kwanza to Gabon, and the Lower Congo Basin is also characterized by several allochthonous salt structures.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California