基于中—西非裂谷系构造演化及沉积充填特征研究,结合区域地质背景,对尼日尔Termit裂谷型叠合盆地的油气成藏特征进行剖析,并探讨其油气富集主控因素.Termit盆地是早白垩世、古近纪2期断陷活动形成的裂谷型叠合盆地,发育1套广泛分布的上白垩统Yogou组海相烃源岩.古近系Sokor组1段和白垩系Yogou组2套储集层以石英砂岩为主,具有较好的孔渗特征,在古近系Sokor组2段区域盖层之下可形成多套有利储盖组合.断裂样式与油气运聚方式决定了构造带油气运聚模式,形成Araga地堑“Y”型油气侧向及垂向运聚模式、Dinga断阶“多阶型”油气垂向运聚模式和Fana转换带“复式”油气运聚模式.油气富集受裂谷盆地构造控制,即2期裂谷作用形成的断裂带控制油气的平面展布,晚期裂谷层序内的有利储盖组合控制油气垂向富集程度.%Based on the tectonic evolution and depositional characteristics of Central-West African Rift System and regional geologic background,the characteristics of oil and gas accumulation in the Termit rift superimposed basin were examined,and the factors controlling oil and gas accumulation there were discussed.The Termit basin is a rift superimposed basin formed by two stages of rifting in the early Cretaceous and Paleogene,where the Yogou Formation marine source rock is widespread.The two sets of reservoirs,the first member of the Paleogene Sokor Formation and the Cretaceous Yogou Formation,dominated by quartz sandstone,have relatively good porosity-permeability characteristics.They can form multiple sets of favorable caprock-reservoir assemblage below the regional caprock of the second member of Paleogene Sokor Formation.It is found that fault pattern and oil and gas migration pattern control the oil and gas accumulation patterns in the basin,including "Y-shaped" hydrocarbon migration and accumulation in the Araga graben,"multi-step" vertical hydrocarbon migration and accumulation in the Dinga faulted terrace,and the "composite" hydrocarbon migration and accumulation in the Fana transfer zone.Hydrocarbon enrichment in this basin was controlled by tectonic evolution of rift basins,that is,fault belts formed during the two stages of riffing controlled the horizontal distribution of oil and gas,while favorable reservoir-caprock assemblages in the sequences formed in the late firing stage controlled the vertical hydrocarbon enrichment.
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