Study on Helium Reservoir Forming Mechanism of Weiyuan Gas Field and Jinqiu Gas Field in Sichuan Basin

The Sichuan Basin is one of the main natural gas production areas in China, and the helium resources of natural gas associated gas are widely distributed. Among them, the Weiyuan Rich Helium Natural Gas Field is the first helium gas field to be industrially utilized in China, with the highest helium content in Weiyuan natural gas reaching 0.342%; Jinqiu gas field is the second natural gas field with high helium content discovered in the basin in recent years, with an average helium abundance of 0.07%. This article analyzes rock and gas samples from Weiyuan and Jinqiu gas fields, and compares them with previous research results. The study shows that the reservoir formation mechanisms of Weiyuan gas field and Jinqiu gas field are different: the main production layer of helium in Weiyuan gas field is the Dengying Formation of the Sinian system, with an average helium content of 0.28%. Helium mainly comes from the basement granite and migrates upward with formation water as a carrier; The helium gas in Jinqiu gas field is mainly produced in the Jurassic Shaximiao Formation, with the highest content of 0.2% in the well. There are multiple sets of helium source rocks, and the Shaximiao Formation sandstone has the highest contribution rate of endogenous helium gas. Helium gas is transported by hydrocarbon gas as the carrier gas, and the differential accumulation of lithological gas reservoirs leads to strong heterogeneity in helium content.