Abstract:

The tight sandstone gas reservoirs of the Xujiahe Formation in the western Sichuan Depression of the Sichuan Basin are characterized by thick sand bodies, poor physical properties, strong heterogeneity, and complex gas-water distribution. These factors significantly challenge the development evaluation and productivity zone selection for this gas reservoir. The second member of Xujiahe Formation in Xinchang-Hexingchang gas reservoir has been chosen as the subject of in-depth research to facilitate efficient evaluation and development. The research includes analyzing both static and dynamic characteristics of the gas reservoir, as well as examining the ancient and modern structural positions, fault characteristics, fractures, and reservoir quality of typical wells. These analyses help to identify the main factors controlling high production in gas wells. By considering the comprehensive effects of various controlling factors and integrating the findings from reservoir formation studies, the pattern of natural gas enrichment and high productivity is explored.The results indicate that the gas wells of the second member of Xujiahe Formation gas reservoir in Xinchang-Hexingchang can be categorized into three types: high yield and high efficiency, medium yield and medium efficiency, and low yield and low efficiency. Wells with good geological conditions—those that are high-yield and high-efficiency or medium-yield and medium-efficiency—are found to have high and stable production. They are primarily located near the north to south fourth-level and fifth-level hydrocarbon source faults, where fractures are well-developed and the thickness of high-quality reservoirs is considerable. The enrichment and high productivity of the gas reservoirs are governed by the interplay of several factors: ancient and modern structures that control the reservoirs, hydrocarbon source faults that dictate enrichment, effective fractures that enhance production, and high-quality reservoirs that ensure stability. These insights provide a solid foundation for the efficient development of gas reservoirs in the region.

Key words: western Sichuan Depression, Xujiahe Formation, tight sandstone gas reservoirs, high-yield enrichment law, Xinchang tectonic belt