Analysis of Petroleum Geological Characteristics in the Eastern of Doseo Basin, Chad

Abstract

Ma Hong, Wang Zhaoming, Du Yebo, Wang Li, Wang Lin, Bai Jianfeng, Hu Jie, Gao Huahua, Gao Simin and Zhou Haiyan

Over the past decade, significant discoveries of oil and gas have been continuously made in the eastern of the Doseo Basin in Chad. Based on a large amount of geochemical analysis data from drilling samples, this paper systematically studies the source rock conditions, reservoir conditions, reservoir-cap combination and migration-accretion characteristics of oil and gas accumulation in the CNPC block within the Doseo Basin. It also makes a preliminary prediction of the favorable exploration areas. The study concludes that: The main favorable source rocks in this area are three sets of Lower Cretaceous rocks, multiple sets of favorable reservoirs, one set of regional cover rocks and multiple sets of local cover rocks. These conditions create favorable conditions for the generation, migration, accretion and accumulation of oil and gas. The Lower Cretaceous Kedeni Formation has a large thickness and wide distribution, high organic matter abundance, mainly type I kerogen, and medium to high maturity of organic matter, which is conducive to the generation of a large amount of oil and gas from source rocks. The Lower Cretaceous Doba Formation, Kedeni Formation and Mangara Formation have multiple sets of favorable reservoirs, providing necessary conditions for the accumulation of oil and gas. The fractured systems formed by multiple tectonic activities in the basin provide convenient channels for the migration and accumulation of oil and gas. In the Kedeni Formation, there are lower generated and upper stored and self-generated and self-stored type oil and gas reservoirs; in the Doba Formation, there are lower generated and upper stored type oil and gas reservoirs; and in the Mangara Formation, there are upper generated and lower stored and self-generated and self-stored type oil and gas reservoirs. Based on this analysis, it is concluded that the main exploration directions for the next step in the oil and gas exploration of the study area should be mainly focused on structural-lithologic oil and gas reservoirs, lithologic oil and gas reservoirs, stratigraphic oil and gas reservoirs and deep oil and gas reservoirs of the Mangara Formation. This research result points out the direction for the subsequent exploration of the study area and is expected to achieve effective replacement of reserves for the Doseo Basin's oil and gas reserves growth and production.

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