中西非裂谷系B盆地构造演化及其对油气成藏的影响研究

Tectonic Evolution and its Influence to Hydrocarbon Accumulation in B basin,Central and Western African Rift System

利用平衡剖面技术,结合区域板块运动和应力背景,对B盆地的演化历史进行了恢复。恢复结果表明B盆地经历了前白垩纪的盆地基底形成期、白垩纪断陷期、晚白垩世晚期-古新世的构造反转期和始新世至今的整体坳陷期四个演化阶段。盆地的构造演化与油气的聚集成藏密切相关。断陷期沉积的大量物质为油气的生成聚集提供了物质来源和储集空间,断陷期长期活动的断裂为油气的运移提供了运移通道,反转期的构造反转提供了圈闭条件同时也造成了一些浅层油气藏的破坏,坳陷期的稳定构造环境为油气的最终成藏提供了良好的保护。

The tectonic evolution history of B basin is restored using balanced cross-section technique,combination with regional plate movement and stress filed background.The result shows that B basin experienced four evolution stages： pre-Cretaceous basement solidification,early-Cretaceous rifting,late-Cretaceous to Paleogene inversion and Eocene to present depression.The tectonic evolution highly influenced the hydrocarbon accumulation in B basin.A great amount of sediments accumulated during the rifting and supplied hydrocarbon resource and reservoirs.The active fault system formed during rifting became the pathway for hydrocarbon migration.The inverted anticlines shaped during late-Cretaceous to Paleogene inversion were traps for hydrocarbon accumulation.At the same time,inversion damaged a lot of shallow reserves.The stable environment protected the trapped hydrocarbon during depression.