Geological characteristics and exploration direction of oil and gas in the passive continental margin basins in the northern part of West Africa

The basins in the northern part of West Africa were lowly explored, but with huge resource potential. Based on the plate tectonics theory and comprehensive study of seismic and geology methods, the researchers analyzed the prototype basins of the main geological periods and compared the structural characteristics of the basins and their differences in sedimentary filling. The discovered oil and gas reservoirs were dissected to establish the mode of hydrocarbon accumulation and point out future exploration direction. The passive continental margin basin group in the northern part of West Africa has undergone three evolutionary stages, that is Precambrian-Permian pre-rift, Triassic-Early Jurassic rift, and passive continental margin basin from Middle Jurassic to the present, and has formed three subclasses of passive continental margin basins, that is fault basins, fault depression basins, and depression basins. The fault basins formed a “single source-tectonic” accumulation model, and the exploration target is mainly structural reservoir combinations of rift strata. The fault depression basins could form “dual source-dual combination” accumulation model. Structural traps of rift strata are mainly on the gentle slope belt of the continental shelf, and reefs and inner karsts are on the edge of the platform. The exploration target in the upper part of the steep slope zone is slope fans formed by large scale slipping-sliding, and the lower part should focus on sandstone structural-lithologic traps of Upper Cretaceous and Lower Cretaceous formed by fans in mature source rock strata. The depression basins are dominated by source rocks of the depression strata, and the main exploration areas are turbidite sandstones in the lower part of steep slope and delta sandstones in the gentle slope of platform. Meanwhile, the reef-beach bodies on the platform margin, the weathering crust karsts of carbonate rock and the karsts in fault zone are also important exploration direction. The research results could provide references for deep-water petroleum exploration selected areas in passive continental margin with lowly exploration degree and poorly data obtaining.