TECTONIC EVOLUTION AND ITS BEARING ON HYDROCARBON DIFFERENT DISTRIBUTION IN OUTENIQUE BASIN, SOUTH AFRICA

The Outenique Basin, located in the very south of the Africa continent, is a typical passive continent margin basin. The Gondawana continent begun to break-up in late Jurassic. The Outenique Basin was then developed with the drifting of the three plates, Africa, South America and Antarctica. The basin has undergone three tectonic evolution stages, rifting, transition and drifting. The Hauterivian and Barremian- Aptian (K1) deposits are the major source rock, which is of II2/III kerogen and prior to gas. The Valangnian (K1) shallow marine sandstone is the major reservoir and the Albian deep-water turbidite sandstone the second. Structural-stratigraphic traps are well developed in the drifting strata, but the structural traps mainly in the rifting stage. Traps formed in rifting stage are rather different with those formed in the drifting period. Up to 2014, 41 oil and gas fields/reservoirs have been discovered. 2.04×10⁷m³ of oil, 2.02×10⁷m³ of condensate and 1.16×10¹¹m³ of recoverable gas reserves have been proved. Facts of discovered oil and gas show that great amount of oil and gas are accumulated in the Valangnian reservoir instead of others, and more reserves have been found in the west of the basin. The analysis of Agulhas fracture suggests that the difference of tectonic activity patterns between the east and west are the main controlling factor of oil and gas distribution in the Outenique basin. Future exploration should focus on the western part of the basin.