西非被动大陆边缘含油气盐盆地构造背景及油气地质特征分析

作    者:刘祚冬,李江海
单    位:北京大学地球与空间科学学院
基金项目:
摘    要:
西非被动边缘含油气盐盆地包括西非安哥拉—喀麦隆段的加蓬盆地、下刚果盆地、宽扎盆地等。认为这些盐盆地从构造、沉积相、油气分布上都具有垂向上的分段性。盆地演化受控于石炭纪末泛大陆裂解及随后南大西洋的张开。盆地演化划分为前裂谷阶段(J3 前)、同裂谷阶段(J3—K1)、过渡阶段(K1)和后裂谷阶段(K2—Q)。由于Tristan热点活动以及热带干旱气候的相互作用,过渡阶段发育厚层阿普特阶盐层,将盆地分为盐上、盐下两套油气系统,控制了油气纵向上的分布。盐盆地以上侏罗统—下白垩统特富湖相Ⅰ型烃源岩、森诺曼阶—赛诺统缺氧环境下形成的Ⅱ型海相烃源岩为主要源岩;大型深水浊积扇体为储层,油气通过同生断层及盐窗等疏导通道运聚至构造圈闭、盐层顺层滑脱引起的拱张圈闭以及一些岩性圈闭中,这些有利的成藏条件相匹配形成了巨大规模油田。
关键词:西非;被动大陆边缘;盐盆地;盆地演化;油气地质特征

Tectonic Evolution and Petroleum Geology Characteristics of Petroliferous Salt Basins Area Along Passive Continental Margin, West Africa

Author's Name: Liu Zuodong , Li Jianghai
Institution: progress at College of Earth and Space Science, Peking University
Abstract:
The passive continental margin of West Africa is becoming one of the most attractive areas for petroleum exploration. Based on the comparison and analysis of Gabon Basin, Lower Congo Basin and Kwanza Basin, the systematic petroleum characteristics were summarized. The history of these basins along the passive margin is controlled by the general framework of the opening of the South Atlantic Ocean,with the breaking up of the proto –continent Pangea. These basins have experienced four tectonic stages of pre-rift (before J3), syn-rift(J3—K1), trastional(K1) and post-rift(K2—Q). Aptian salt, which relates to Tristan hot spot activity and arid climate at that time,controls vertical distribution of hydrocarbon,and separate the upper salt petroleum system from the lower one in these basins. Came room-Angola salt basin group,in which Late Jurrasic-Early Cretaceous deposition has deep lacustrine hydrocarbonrich sources,and Cenomanion-Satonian and Cenozoic marine shale is also the main sources; transitional stage deposited very thick evaporate rocks which are the most important cap in these basins. The reservoirs are the Cenozoic turbidite rock and the common traps are salt-related structures and stratigraphic lithologic traps while syngenetic faults and salt windows serve as excellent channels for migration of hydrocarbon. All these conditions match with each other and favorable to form the large-scaled oil fields.
Keywords: West Africa; Passive continental margin; Basin evolution; Salt Basin; Petroleum geology
投稿时间: 2009-04-21  
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