Depositional Micro-facies Study Of SⅢ Oil-bearing Formation And Delta Inner Front Depositional Model Established Of Duandong In Beiyi Area

Duandong in Beiyi area, on the Sartu anticline of the Daqing Oilfield, is located between the north of Sazhong area and the east of No. 98 fault. Sartu reservoir is the river-delta depositional system, while its interlayer,intraformational and plane heterogeneity are very serious. In 1960, Sartu reservoir began to develop. At present, with using water flooding and polymer flooding development, Sartu reservoir has entered the high water-cut later stage. Further, to improve the development effect of oil field and enhance oil recovery, the study of the reservoir depositional model is of much significance and necessary.In this research, with many wells and layers, it is very difficult to recognize the space of the single sand body, find the origin of the single sand body and carry out hierarchical division of the single sand body. Therefore, based on the core, drilling, logging and other materials of this area with high-resolution features, in combination with the depositional background, micro-facies types and depositional models of this area were established. Under third encryption well conditions, the hierarchical division and contrasts of the single sand body were carried out. Moreover, high-resolution isochronic stratigraphic framework was established. By the correlation of lithology and electric property, at first, establish the electrofacies model with 1 depositional facies, 1 subfacies, 7 micro-facies, then recognize single-well micro-facies layer by layer, and finally, combine the plane facies and draw the map of time units-plane depositional micro-facies. On the basis of the study of the depositional micro-facies, three kinds of underwater depositional models of the delta inner front subfacies were established, namely: 1. the branched depositional model of delta inner front sand body; 2. the pod-like depositional model of delta inner front sand body; 3. the transitional depositional mode of delta inner front sand body between above two models. Combining with the plane micro-facies of dense well network area, a typical contact relationship between plane sand body and profile depositional micro-facies was established.