西非被动大陆边缘构造-沉积演化及其对生储盖的控制作用

西非海岸属典型的被动大陆边缘,经历了前裂谷、裂谷和被动陆缘等三个演化阶段,北段与中南段盆地裂谷作用的时间和方式不同。在由构造—沉积控制的盆地发展演化过程中发育三套主力烃源岩,即裂谷期盐下湖相页岩、被动陆缘期盐上海相页岩以及浅海相—三角洲相页岩;发育裂谷期湖相碎屑岩、被动陆缘期碳酸盐岩、滨岸砂岩、浊积体和三角洲砂岩等多套储层。阿普特盐岩为主要的区域盖层,形成了裂谷期的断块、断背斜、盐岩构造以及与被动陆缘期同生长断层相关的滚动背斜等众多构造和圈闭。

Toctonic-Sedimentary Evolution and its Control on Source-Reservior-Cap Rocks in Passive Continental Margin, West Africa

Hydrocarbon resource is rich in West Africa.The coast region along West Africa belongs to typical passive continental margin,which experienced three evolution stages,i.e.the pre-rifting stage during Late PaleozoicEarly Mesozoic(continental craton stage)time,the rifting stage since Middle-Late Mesozoic time and the passive continental margin stage by the end of Mesozoic-Tertiary time.Genesis of the rift in the northern part is different with that in middle-southern part of the basin in rifting time and ways.During the evolutionary process of the basin that was controlled by the regional tectonic-sedimentary development,three main sets of source rocks and several sets of reservoir rocks developed.The source rocks include the pre-salt lacustrine shale in the rifting stage and the post-salt marine shale and the marine-delta shale in the passive continental margin stage.The reservoir rocks are the lacustrine clastic rock in the rifting stage,and carbonate rock,shoreside sandstone,turbidite and deltaic sandstone in the passive continental margin stage.The Aptian salt rock acts as the main regional cap and various structures and traps form,such as fault-blocks,fault-anticlines,salt structures,rolling anticlines,growth fault and others,which control the hydrocarbon enrichment and distribution in the coast region.