--> --> Geodynamic Characteristics and Their Effects on the Petroleum Geology Conditions for Passive Rift Basins in the Central-Western Africa Region

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Geodynamic Characteristics and Their Effects on the Petroleum Geology Conditions for Passive Rift Basins in the Central-Western Africa Region

Abstract

Recently, the significant breakthrough has been achieved for petroleum exploration in the Central-Western Africa Rift basins, which is a hotspot for petroleum geologist. The exploration practice showed that there were similarities and differences for the hydrocarbon accumulation conditions and rules in the rift basins of the central-western Africa region. Combined with the regional background information and data from wells, geology and geophysics in the central-western Africa rift basins, the paper concluded that three rifting-sagging stages and two structural inversion events developed in the basins since early Cretaceous, and the first rift developed in the early Cretaceous is typical passive rift. By systematic analysis and comparison the difference of the Central-Western Africa Rift basins and active rifts in Eastern China, the author summarized that the passive rift basin was formed by crustal extension induced by non-mantle upwelling, and the scale of mantle upwelling is smaller than active rift, which resulted in the significant difference between passive and active rifts in terms of thermal history, subsidence history in rifting period, structural style of major faults and sediments in sagging stage, and these difference directly affected the petroleum geology conditions in the passive rift. Based on the geodynamic and geological characteristics of passive rift basin, five unique geological features were concluded such as source rock, reservoir in sagging period, controlling factors for regional cap rock and major play types, favorable accumulation zone and major trap types.