西非Termit叠合裂谷盆地构造沉积演化及控藏机理

基于区域地质背景分析，充分应用钻井与地震资料，开展Termit叠合裂谷盆地构造沉积演化及其控藏机理研究。研究表明：Termit盆地主要经历3大构造沉积演化阶段：1早白垩世裂谷期，以湖泊、三角洲沉积为主；2晚白垩世坳陷期，以浅海、三角洲和远岸水下扇沉积为主，发育主力烃源岩；3古近纪裂谷期，以短轴辫状河三角洲、湖泊沉积为主，发育主力储集岩与区域性盖层。构造沉积演化控制了生、储、盖层，断裂体系及构造圈闭的展布，决定了盆地油气的空间分布：1沉积演化控制了生、储、盖层分布，形成了上、中、下3套成藏组合，控制了油气纵向分布；2构造演化控制了输导体系和构造圈闭分布，形成了多个复杂构造带，控制了油气平面分布；3沉积相带控制储集砂体微观结构及宏观展布规律，控制了油气富集程度。综合地质研究成果，建立叠合裂谷复合油气成藏模式，明确白垩系-古近系下一步勘探领域，有效指导盆地油气勘探。

Tectonic-sedimentary evolution and reservoir controlling mechanism of Termit superimposed rift basin in West Africa

Based on regional geologic background analysis, and making full use of well drilling and seismic data, a study is conducted on the tectonic-sedimentary evolution and reservoir controlling mechanism of Termit superimposed rift basin. The research shows that Termit Basin mainly experienced three tectonic-sedimentary evolutionary stages. The first stage was the Early Cretaceous rift period dominated by lacustrine and delta sediments; the second stage was the Late Cretaceous depression period dominated by shallow sea, delta and offshore submarine fan sediments, when chief source rocks were developed; the third stage was the Paleogene rift period dominated by short-axis braided river delta and lacustrine sediments, when chief reserving rocks and regional cap rocks were developed. The distribution of source-reservoir-cap, fault system and structural trap is controlled by tectonic-sedimentary evolution. This further determines the spatial distribution of basin hydrocarbons as below. Firstly, the source-reservoir-cap distribution is controlled by sedimentary evolution, thus forming three sets of upper, middle and lower reservoir assemblages and further controlling the longitudinal distribution of hydrocarbons. Secondly, the distribution of migration system and structural trap is controlled by sedimentary evolution, thus forming multiple complex tectonic zones and further controlling the horizontal distribution of hydrocarbons. Thirdly, the sedimentary facies belts determine the micro-structure and macroscopic distribution laws of reserving sands as well as hydrocarbon enrichment degree. According to the comprehensive geological research result, the composite hydrocarbon accumulation model of superimposed rift was established to make clear the next Cretaceous-Paleogene exploration field and effectively guide the oil-gas exploration in the basin.