Petroleum Geological Characteristics and Main Control Factors of Hydrocarbon Accumulation in Termit Basin, West Africa

The Termit basin is a very important exploration and development block of CNPC in Africa. The petroleum geological characteristics and main controlling factors of hydrocarbon accumulation have been studied base on the drilling, analysis and seismic data ,in the Termit basin. The research shows that: ① The Termit basin has undergone three tectonic evolution stages: pre-rift period, synrift period and post-rift period, and the meso-Cenozoic superimposed rift basin was formed by two stages of early and late rifting during synrift period. The macrostructure features of "east-west zoning and north-south segmentation" control the formation and distribution of traps. ② The Upper Cretaceous Yogou Formation is widely distributed (18000 km²), with a large thickness (600～1400 m) and moderate maturity (Ro: 0.7%～1.3%) Marine source rocks, with Marine delta developed at the top of Upper Cretaceous Yogou Formation, braid river delta sand body of Paleogene Sokor1 member, and mudstone cover of Paleogene overlying Sokor2 formation regionally distributed, formed a good reservoir-cap association. ③ The main controlling factors of hydrocarbon accumulation in Paleogene and Cretaceous are identified. Paleogene is a secondary hydrocarbon reservoir with "lower generation and upper reservoir", the plane and vertical distribution of oil and gas is controlled by hydrocarbon generation focus, regional cap layer, oil source fault and dominant sedimentary facies, while Cretaceous is a "self-generated and self-storage" primary reservoir, and oil and gas enrichment is controlled by regional tectonic activity intensity and Cretaceous insider structure. ④ A cross-generation hydrocarbon accumulation model based on widely covered Marine source rocks is constructed, and the Dinga fault-step belt, Fana uplift and Araga Graben are identified as favorable zones for hydrocarbon exploration in Paleogene, while the Moul sag and the southern part of Dinga fault-step belt are favorable zones for hydrocarbon exploration in Cretaceous. Geological knowledge guided exploration and deployment, achieved a major exploration breakthrough in the Termit Basin in Niger, and accumulated proved oil geological reserves exceeded 700 million tons, laying a solid foundation for CNPC to increase overseas oil and gas reserves and production.