Hydrocarbon Accumulation Characteristics and Future Exploration Direction in Senegal Basin, Northwest Africa

The Senegal basin in Northwest Africa is a giant rift−passive margin superimposed basin floored by the Precambrian−Paleozoic crystalline basement. Based on combinations of seismic, drilling, well logging data and the latest international commercial petroleum databases and exploration results, along with understanding of regional geological history (tectono−sedimentary evolutions), this study was focused on hydrocarbon accumulation conditions and patterns and enrichment rules of hydrocarbons, and predicted the future direction of exploration in the Senegal basin. The study shows that the basin experienced three tectonic evolution stages: pre−rift, syn−rift, and passive margin. The current structure of the basin is characterized by “a gentle northern slope and a steep southern slope”, specifically, the narrow continental shelf and gentle continental slope in the north the wide shelf and steep slope in the south. The basin has lacustrine source rocks deposited during the rifting period and marine source rocks deposited in the passive margin period. The lacustrine source rocks have a more significant contribution to petroleum accumulations in the Cretaceous reservoirs in deepwater areas. Marine source rocks became mature until the thicker overlying sediments deposited. Three types of hydrocarbon accumulation models were recognized: ① lower−generation and upper−storage in the continental shelf area characterized by delta−front turbidite sandstones charged through unconformity and faults. ② lower−generation and upper−storage at the foot of the continental slope dominated by near−source fault−sandstones configuration. ③ lower−generation and upper upper−storage in deepwater and ultra−deepwater areas dominated by structural−stratigraphic turbidite trap through vertical migration. The shelf−margin delta−front sandstones, turbidite channels and submarine fan lobes at the slope foot, turbidite fan in the deepwater areas are favorable targets for exploration. Large structural−stratigraphic traps in deepwater areas are the most important exploration target in the Senegal basin.