DISTRIBUTION OF THE SOURCE ROCKS AND MECHANISMS FOR PETROLEUM ENRICHMENT IN THE CONJUGATE BASINS ON THE SOUTH ATLANTIC PASSIVE MARGINS: CASES STUDIES FROM THE SANTOS AND NAMIBE BASINS

The Santos Basin in Brazil and the Namibe Basin in West Africa are the conjugate basins on the South Atlantic passive margin. The basins have undergone a complex history that can be divided into several basin evolution stages, i.e. the rift stage (Late Jurassic to Early Cretaceous), transitional stage (Early Cretaceous Aptian) and post-rift stage (Late Cretaceous to Holocene). A striking feature of the transitional stage is the widespread evaporite deposition of the Aptian salt. The characteristics of the Lower Cretaceous sub-salt rift, the thickness of the salt and the Upper Cretaceous supra-salt strata are controlled by the asymmetric extension of the South Atlantic. The mechanisms for petroleum enrichment in the Santos and Namibe Basins are controlled by the development of the Lower Cretaceous sub-salt lacustrine source rocks and the maturity of the Upper Cretaceous supra-salt marine source rocks. The Lower Cretaceous sub-salt structural and lithologic traps in the deep to ultra-deep water are the significant exploration targets for giant oil and gas fields and the Upper Cretaceous supra-salt structural and lithologic traps interrelated to the salt tectonics in the deep troughs under the shallow water are also the important for exploration of large and middle fields.