东非大陆边缘构造演化过程与油气勘探潜力
Tectonic evolution and petroleum exploration prospect of East Africa
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摘要: 提要:近年来,东非大陆边缘油气接连获得大突破,已成为世界油气勘探的热点。与西非和北非相比,东非油气勘探和研究程度均很低,尤其经历错综复杂的构造演化过程后,盆地构造、沉积与油气系统及其三者之间的相互作用关系十分复杂,不利于对东非油气勘探前景的分析和判断。本文通过对东非大陆边缘形成与演化过程的探讨,并结合现今盆地结构和油气发现状况,研究认为,东非大陆边缘先后经历了Karoo陆内裂谷、侏罗—白垩纪裂谷两期裂谷和一期被动陆缘作用阶段。两期裂谷发育多套烃源层系,并与被动陆缘阶段的三角洲-深水浊积扇储层时空上构成较好的油储关系,两者均受控于东非复杂构造演化作用,构造对油藏系统的改造或破坏作用影响了东非油气富集规模和类型。Abstract: Abstract:At present, East Africa continental margin which has won a big breakthrough in oil and gas exploration has become the hot spot of the world petroleum exploration. Compared with West and North Africa, East Africa is at the very low oil and gas exploration and research level. After complicated tectonic evolution, the basin structure, deposition and petroleum system as well as their interaction have become very complex, which is not favorable for the analysis and judgment of the petroleum exploration prospect of East Africa. Studies of the evolution process of the East Africa continental margin in combination with the current basin structure and oil and gas discovery indicate that the continental margin of East Africa has successively experienced Karoo intracontinental rifting, Jurassic and cretaceous rifting and a passive epicontinental action. Two rifts provided good sedimentary environments such as lacustrine facies and lagoon facies, which formed multiple hydrocarbon source formations. In space and time, they constituted a good hydrocarbon-reservoir system with delta and deep-water turbidite fans in the passive continental margin stage. In addition, they were both controlled by complex tectonic evolution which decided the size of reservoirs and the style of hydrocarbons.
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