Study on the development characteristics of deep shale gas reservoirs in western Chongqing and their influence on reservoir quality

Deep shale gas is an important replacement field for China’s shale gas development. Shale gas production is not only restricted by engineering factors, but also affected by reservoir quality. The shale of Wufeng Formation Longmaxi Formation in Dazu Block, western Chongqing, is selected as the research object, and the development characteristics of shale laminae are compared and analyzed. Through the correlation analysis of the extracted laminae development index and reservoir quality factors, the impact of laminae development on its reservoir quality is studied, so as to provide basis and support for the fracturing construction of shale gas reservoirs in this block. The research results indicate that: According to the shale mineral composition, the shale reservoir laminae have many types, including siliceous laminae, clay laminae, calcareous laminae and organic laminae. pyrite laminae can be seen in some areas, and the laminae are mostly plate, strip and lenticular. The most common lamina groups include siliceous clay lamina group, siliceous organic lamina group, and clay organic lamina group. Overall, the lamination of S111-14 is relatively underdeveloped, the lamination of S111-13 and S111-12 are relatively similar, and the lamination of S111-11-the top of Wufeng Formation is most developed. Through the reservoir quality factor model, it is found that there is a correlation between the lamination development index and the reservoir quality factor. The correlation between siliceous laminae and reservoir quality factors is the highest. The top of S111-11-the top of Wufeng Formation has high quartz content and good brittleness. The laminae are mainly siliceous laminae, which is conducive to fracturing.