东非欧加登盆地油气成藏条件及勘探潜力分析

Analysis of Oil and Gas Accumulation Conditions and Exploration Potential in the Ogaden Basin of East Africa

摘要: 东非是中国石油企业海外油气项目的重点目标区之一，其中位于埃塞俄比亚的欧加登盆地是一个勘探程度较低的大型整装盆地，面积35 × 10⁴ km²，天然气资源量5 × 10¹² m³，石油资源量60 × 10⁸ t，具有较大的勘探潜力。利用上世纪中期以来尤其是近年勘探取得的大量物探及地质资料，对欧加登盆油气成藏条件及油气勘探潜力进行研究，明确欧加登盆地下一步勘探方向。通过研究，将该区构造划分为7个一级构造单元，并将最有利于油气藏形成的中部坳陷划分为6个二级构造单元；明确了二叠系Bokh组泥页岩为主要烃源岩；确定了盆地内二叠系及侏罗系发育的三套主要生储盖组合；已发现的含油气藏圈闭主要为背斜及断鼻圈闭，在斜坡背景下发育的岩性及地层圈闭是潜在的有利圈闭类型；建立起欧加登盆地油气成藏模式；提出中央低凸起及洼陷周边的斜坡是下步重点勘探目标。

Abstract: East Africa is one of the key target areas for overseas oil and gas projects, among which the Ogaden Basin in Ethiopia covers an area of 35 × 10⁴ km², with natural gas resources 5 × 10¹² m³and oil resources 60 × 10⁸ t, which has great exploration potential. Based on the large amount of geophysical and geological data obtained since the middle of the last century, especially in recent years, this paper studies the oil and gas accumulation conditions and oil and gas exploration potential in the Ogaden Basin, and clarifies the next exploration direction of the Ogaden Basin. Through the study, the structure of the area is divided into 7 first-order structural units, and the central depression that is most conducive to the formation of oil and gas reservoirs is divided into 6 secondary structural units. The mud shale of the Permian Bokh Formation is identified as the main source rock, the three main sets of bio-reservoir cap assemblages developed in the Permian and Jurassic in the basin are determined, the discovered traps of oil-bearing reservoirs are mainly anticline and fault-nose traps, and the lithology and stratigraphic traps developed in the background of the slope are potential favorable trap types, the hydrocarbon accumulation model of the Ogaden Basin is established, and the slopes around the central low bulge and sag are proposed as the key exploration targets in the next step.