Main Controlling Factors and Dominant Reservoir Series Analysis of Es3 in the Qibei Area of Qikou Sag

Based on analysis of geophysical data such as core observation, rock slices identification, physical property, scanning electron microscope, X‐ray diffraction, logging data etc., 16 factors of sedimentation, diagenesis, fluid pressure, and their relationships with reservoir physical property were analyzed, and the results indicate sedimentation is the internal factor controlling the reservoir property, diagenesis is the external and final decisive factor and abnormal fluid pressure is an important factor preserving the deep reservoir property. Quantitative characterization of diagenesis indicates that compaction and dissolution are more important than cementation and they respectively cause porosity change of ?23.6% and 7.7% and ?6.2%. Through optimizing 11 main controlling factors and constructing reservoir evaluation index (REI) according to the hierarchical cluster and principal component analysis, reservoir classification standard was established and reservoirs were divided into four classes. The studies show that Es₃² SQ4 consists mainly of class 1 and II, while Es₃² SQ6 is mainly of class III and II; the favorable zone is the north and south slope of Qibei sub‐sag and the Liujianfang fault‐nose. The successful application of the quantitative and comprehensive evaluation in the Qibei area verifies the advanced, practicable method of less artificial factor is suitable for the low porosity and permeability reservoir.