Microscopic Pore Structure Characteristics and Classification Evaluation of Tight Sandstone Gas Reservoirs in the Zhongba Area of Western Sichuan
The tight sandstone reservoirs in Zhongba Area of western Sichuan have experienced complex sedimenta-tion and diagenesis evolution,resulting in poor reservoir physical properties,complex pore structure and strong heter-ogeneity,which makes it difficult to effectively evaluate the reservoir and to predict the"sweet spots".To address this issue,this study focused on the tight sandstone reservoirs of the Xujiahe Formation in the Zhongba Area,and systematically evaluated the microscopic pore structure characteristics of the reservoirs based on rock physics experi-ments including porosity and permeability from gas logging,casting thin sections,high-pressure mercury intrusion,and scanning electron microscope.Additionally,reservoir classification and well logging evaluation are conducted to determine the development and distribution characteristics of high-quality reservoirs with flow unit theory and BP neural network technology.The results show that the physical properties of the target reservoirs in the study area are poor,the reservoir space is mainly secondary intergranular pores and dissolution pores,the throat types are mainly point-like and necked,and the pore size is mainly nano-submicron.Reservoirs are classified into four types(Ⅰ-Ⅳ)based on flow unit.The Flow Zone Index(FZI)can effectively characterize the pore structure and flow charac-teristics of the reservoirs.Type Ⅱ and Ⅲ reservoirs are mainly developed in the second member of Xujiahe Forma-tion in the study area,and type Ⅰ reservoirs are developed in the ZB9-65-46 well field in the middle of the gas res-ervoir.The main structural reservoirs in the Zhongba Area are thick,predominantly type Ⅱ,while the reservoirs in the Laopingba and structural saddles are mostly thin layers,mainly type Ⅲ.Vertically,the effective reservoirs are primarily developed in the upper part of the second member of Xujiahe Formation,and its thickness accounts for 73.60％of the total reservoir thickness.The research results provide a scientific basis for reservoir evaluation and effi-cient development of similar tight sandstone gas reservoirs.
万方数据
维普
