FRACTURE CHARACTERISTICS OF LONGMAXI SHALE IN SOUTHERN SICHUAN

There are huge reserves of shale gas resources in China, and the Sichuan Basin is the main production area. An important indicator in shale gas exploration and development is fracture characteristics and carries the two major functions of gas storage and transportation channels. Therefore, understanding the microscopic characteristics of reservoir fractures is of great significance for evaluating the gas content of the reservoir and the development prospects. In this paper, the main research object is the core of shale gas Well Lu 201. The well is located in the main shale gas production area in Southern Sichuan. With handheld microscope and stereo microscope as the main observation tools, observation experiments on the core were carried out. This paper also uses image software to reconstruct images of the core surface, statistically analyses the types, reservoir fracture characteristics, development characteristics and mineral characteristics, and successfully constructs two-dimensional shale fracture models. Through microscope observation this paper finds that: (1)Fractures in the 1st and 2nd sub-layers of the Longyi 1 sub-member of the Longmaxi Formation and Wufeng Formation shale reservoirs are mostly short fractures, accounting for 79.8% of the total fractures, with fracture length/core circumference less than 25%. (2)Fractures are well developed in the core of the Longyi 1 sub-member 1st small layer, and the fractures are mainly parallel to the bedding planes. The natural fracture number in the 2nd small layer of the Longyi 1 sub-member is slightly lower than that of the 1st small layer, while in the Wufeng formation only a very small number of natural fractures are observed. (3)The main minerals observed on the surface of the core are pyrite and calcite. The main innovation of this paper is the statistical analysis of the fracture characteristics of the Longmaxi Formation shale reservoir in Southern Sichuan through an intuitive method. and this research is of great significance for shale gas production and reservoir gas flow analysis.