乌尔逊凹陷大磨拐河组三角洲储层特征

THE CHARACTERISTICS OF DELTA RESERVOIR IN DAMOGUAIHE GROUP IN WUERSHEN DEPRESSION

乌尔逊凹陷面积2350km^2,是在前中生代褶皱基底上形成的断陷盆地。三角洲沉积主要发育在大磨拐河组中上部,可分为河控三角洲和浪控三角洲两种类型。通过砂体形态、沉积层序、成分与结构及粒度分布,对三角洲储集层的沉积学特点进行了研究。三角洲储集层经历了复杂的成岩历史,压实作用导致了早期孔隙度的降低,自生胶结物充填了粒间孔隙,溶解作用产生次生孔隙。储层性质是成岩强度的函数。据影响储层性质的主要成岩事件或成岩相,可将三角洲砂体划为3类储层类型:①碳酸盐胶结型;②压实—充填型;③不稳定碎屑溶蚀型。三角洲砂体的储集特征受砂体微相和成岩作用的双重控制。

wuershen depression, a fault-subsided basin formed on the premesozoic fold basement, is about 2350km^2. Deltaic deposit, mainly developed in the middle and upper parts of Damoguaihe group, could be dividede into two kinds: river dominated delta and wave dominated delta. We studied the depositional characteristics of delta reservoir from the shapes of sandbodies, sedimentary succession, component, structure and size distribution. The delta reservoir underwent a complicated diagenetic history. The compaction resulted in a decrease in original porosity. The authigenic cements filled the intergranular space. The dissolution made secondary porosity. The reservoir properties were the function of diagenetic strength. According to the major diagenetic events or diagenetic facies which affected the reservoir proporties the deltaic sandbodies were divided into three kinds of reservoir: (1) carbonate cemention type, (2) compaction-filling type, (3) unsteady clastics dissolution type. The reservoir characteristics of deltaic sandbodies were controlled by both the microfacies and diagenesis of the sandbodies.