STRUCTURAL CHARACTERISTICS OF WEST AFRICA IN PRE-SALT RIFT STAGE AND THEIR GEOLOGICAL SIGNIFICANCE

Recent hydrocarbon discoveries have proved that the pre-salt rift stage of the West Africa coastal basin has great oil and gas potential. Based on the data from the regional seismic surveys, this paper made a detailed study on the structural patterns of pre-salt rift. It shows that the pre-salt rift in West Africa is composed of two stages: early rift stage and later depression stage. On the plane, several first-order tectonic units, such as the Inner sub-basin, the Central uplift and the Outer sub-basin, are identified. Within the outer sub-basin, there occur alternated secondary tectonic units, which includes uplifts and depressions under the control of faulting and the pattern of east-west zonation and north-south segmentation are rather clear. The structural patterns of pre-salt rift stage indicate that the rifting started earlier and lasted longer in the north comparing to the south. The evolution of rifting has great significance to the generation of petroleum system and the pre-salt-rift stage is a favorable target for hydrocarbon exploration.