低幅度构造-岩性边底水油藏特征及其成藏机制——以塞152油藏为例

Characteristics and Formation Mechanism of Low-Relief Structural-Lithological Reservoir with Edge and Bottom Water:A Case from the Sai 152 Pool,Ordos Basin

鄂尔多斯盆地内陕北斜坡构造上延长组长2段油藏分布分散,成藏机制特殊。为指导长2段油藏的下一步勘探,利用岩心、测井、录井和试油资料,研究了塞152油藏的构造、沉积和油藏特征,探讨了油藏成藏机理。研究结果表明塞152油藏为一个发育在低幅度构造上的构造—岩性边底水油藏。砂体展布受三角洲前缘水下分流河道和河口坝微相控制,储层孔隙类型以粒间孔为主,属于中-低孔、低-特低渗储层。油层分布受构造和岩性双重控制。由于构造幅度低且夹层发育,导致油水分异不彻底,不具有统一的油水界面,但发育了边底水。油藏的形成与油气沿延长组顶面不整合面和基底断裂的垂向输导以及目的层内的水平运移关系密切。

The second member reservoir of Upper Triassic Yanehang Formation within the Yishan slope of Ordos Basin is distributed wildly and exhibits specific genesis. To offer guidanlines for the next exploration of this member, the structure, deposition and reservoir characteristics and formation mechanism of Sai 152 pool were explored based on cores, well-logging, mud-logging and oil-testing data. It can be concluded that the development of Sai 152 pool at a low relief structure setting results in a structural-lithological reservoir with edge and bottom water. The sandstones are controlled by underwater distribution channels and mouth bars of delta front. The reservoir develops intergrain pores, mostly with medium-low porosity and low-very low permeability. The oil distribution is dominated both by structure and lithology. The oil and water separation is not complete because of low relief structure and frequent intercalations. This could have led to a nonnuniform oil/water contact; however, the reservoir has edge and bottom water. The formation mechanisms of this reservoir are associated with the first vertical migration along top uncomfortable surface of Yanchang Formation and basement fault and the subsequent horizontal migration within the sandstones connected with the target laterally.