Helium dynamic accumulation process in the Hetianhe gas field, Tarim Basin, northwest China

Helium (He) is considered an indispensable rare resource due to its critical applications in high-tech fields such as low-temperature superconductivity, magnetic resonance imaging, and aerospace. However, the sources of helium and its accumulation processes in hydrocarbon basins remain unclear. The Hetianhe gas field, as China's first supergiant He-rich gas field, provides a natural laboratory for studying the mechanisms of helium enrichment. By analyzing the primary gas components and noble gas data from natural gas wells in the Hetianhe gas field, and comparing these with geological data from known He-rich gas fields worldwide, a detailed anatomy of the Hetianhe helium-rich gas field is conducted from three aspects: generation, migration, and accumulation. The Hetianhe gas field is not only uniformly rich in helium but also shows promising exploration potential. Helium tends to accumulate in structural highs within the field. Quantifying the helium isotope ratios (R/Ra) reveals that the helium in the Hetianhe gas field is of typical crustal origin. From a "source-reservoir dual control" perspective, it is calculated that 62% of the helium is sourced from the basement helium source rocks, while 38% comes from sedimentary helium source rocks. The study indicates that the Paleoproterozoic granite basement provides a sufficient helium source, with the fault systems serving as effective migration pathways for helium. The concentration of ⁴He and ²⁰Ne in natural gas is positively correlated, which reflects the close relationship between He migration and groundwater. In addition, N₂ and He in natural gas in the Tarim Basin show a good positive correlation, which further indicates that ⁴He dissolves into the groundwater system before degassing into a gas reservoir and that the variations in the ⁴He concentration in the gas phase are caused by the difference of natural gas lateral migration and charging intensity. Notably, a comparison with the reservoir characteristics of globally recognized He-rich fields reveals that "shallow depth, low pressure, and high structural uplift" are key geological factors for helium accumulation.