高邮凹陷缓坡带戴南组隐蔽油藏成藏特征及主控因素分析

Analysis of accumulation characteristics and key control factors of Dainan Formation subtle oil reservoir in the gentle slope belt of Gaoyou Sag

高邮凹陷缓坡带戴南组发育多类型隐蔽油藏,成藏条件复杂,搞清其成藏特征与成藏主控因素对指导该区油气勘探意义重大。研究表明,缓坡带戴南组主要发育四种类型隐蔽油藏:断层—岩性复合油藏、砂岩上倾尖灭油藏、透镜体油藏、地层超覆油藏,各类型油藏具有不同的成藏特征。成藏主控因素主要有三点:烃源岩、有效输导体系共同控制油藏丰度;砂体类型、发育规模共同控制油藏平面分布特征;局部盖层厚度、砂泥对接关系共同控制油藏纵向规模。

There are several types of subtle oil reservoirs of Dainan Formation, with complex hydrocarbon accumulation conditions, in the gentle slope belt of Gaoyou Sag. So a correct understanding of the accumulation characteristics and main controlling factors is of great significance to the petroleum exploration in this area. The study result shows that four types of subtle oil reservoirs are developed in Dainan Formation of the gentle slope belt,which include fault - lithologic reservoir, sandstone updip thinning out reservoir, sand lens reservoir, and stratigraphic overlap reservoir. Each type of reservoirs has different hydrocarbon accumulation characteristics. Three main factors, which control the formation of the subtle oil reser- voirs, are as follows： hydrocarbon source rock and effective migration pathways both controll the abundance of reservoirs, the kinds and the scale of sand bodies which together control the horizontal distribution characters of reservoirs, and the thickness of local caprocks and the sand - shale contact relation of around faults which jointly control the longitudinal pool size.