The factors responsible for the unusual content of helium-rich natural gas in the Weihe Basin, Shaanxi Province

The isotope analyses of the helium-rich natural gas based on 22 wells of the Weihe Basin show that the helium gas belongs to crust-derived helium with a little mantle-derived one. Based on analyzing anomalies of helium and characteristics of the Weihe Basin, the authors summarized three impact factors of helium anomalies in the Weihe Basin: ①high degree of hydrothermal fluid activity, thin basin crust and Moho rise, which are favorable for helium transport; ②the radioactive element decay of the granite and strata provides abundant gas for the helium accumulation; ③the fracture system of the Weihe Basin not only provides pathway for the helium migration but also releases helium and serves as space for helium accumulation.