Exploration discovery and hydrocarbon accumulation characteristics of the Doseo strike-slip and reverse basin

Several international oil companies had conducted petroleum exploration, but failed to make any commercially viable discoveries in the Doseo Basin for over 30 years. An integrated analysis of the basin based on the latest seismic and well logging data was completed to establish the hydrocarbon accumulation model and find the potential petroleum plays. The Doseo Basin in Chad is a Mesozoic-Cenozoic lacustrine rift developed on the basement of Precambrian crystalline basement in the Central African Shear Zone. It is a half graben rift controlled by the strike slip fault at the northern boundary, and can be divided into two depressions, an uplift and a slope by the Central Uplift. The basin experienced two rift periods in the Cretaceous and was strongly reversed with the denudation thickness reached 800–1000 m during the Paleogene, and then it entered the depression period and extinction period. Normal faults and strike slip faults are developed in the basin, and the boundary faults are reverse faults that starts as normal faults. Compression anticline, fault nose, complex fault block and other types of structures are developed associated with flower structures. The Lower Cretaceous is the main sedimentary strata, which are divided into Mangara Group, Kedeni Formation, Doba Formation and Koumra Formation from bottom up. Two transgressive-regressive cycles developed in the Lower Cretaceous with mainly lacustrine, braided river delta, fan delta facies sandstone and mudstone. The effective source rock in the basin is the Lower Cretaceous deep lacustrine mudstone with the type I and type II1 organic matter. Inverted anticlines and fault blocks with complex faults are the main trap types. The Kedeni Uplift is the most favorable play, followed by the Northern Steep Slope and Southern Gentle Slope. Lateral sealing capacity of faults controls the reserve abundance.