鄂尔多斯盆地陕北斜坡东部三叠系长2油藏分布规律

鄂尔多斯盆地陕北斜坡为一平缓的西倾单斜,构造简单。通常认为包括长2油藏在内的三叠系延长组油藏的形成和分布主要受沉积相控制,油藏类型主要为岩性油藏,构造等其他因素对油藏的形成和分布并不起重要控制作用。但研究发现,陕北斜坡三叠系长2油藏的形成与富集实际上受沉积相带、鼻状隆起背景、断裂、水动力等多重因素控制。鼻状隆起,尤其是大型鼻状隆起的围斜部位油藏最为富集;断裂是长2油藏形成和分布的重要控制因素;水动力条件是油藏上倾方向重要的遮挡因素之一。因此,长2油藏的类型复杂多样,除岩性油藏外,以构造-岩性、构造-水动力油藏为主的复合油藏可能是该区长2油藏的主要类型。图5参23

Law of petroleum accumulation and distribution in Triassic Chang 2 oil-bearing Formation in eastern North Shaanxi Slope, Ordos Basin

The formation and distribution of Chang 2 accumulations in Triassic Yanchang Formation in the North Shaanxi Slope is considered to be controlled by sedimentasy facies,and the accumulations are lithologic,on which the structural and other factors are believed to have no important effect. The reason is that the Slope is a large smooth monocline dipping westward and characterized by simple structure without folds and faults.The present study shows that they are controlled by multiple factors,such as sedimentary facies,the background of nose-shaped uplift,faults,hydrodynamics,etc.The background of nose-shaped uplift is important for the formation and enrichment of the accumulations.Faults as migration pathways are important to the formation and distribution of the accumulations.Hydrodynamic condition is a significant factor for updip direction barrier.Besides lithologic accumulations,structure-lithologic and structure-hydrodynamic composite accumulations are possibly the main types of the Chang 2 accumulations.