Hydrocarbon–Helium Coupled Accumulation Processes and Formation Mechanisms of Helium-Rich Gas Fields in the Southwestern Ordos Basin

Helium is a critical strategic resource, with industrial helium primarily derived from helium-rich natural gas fields. Numerous large-scale natural gas fields with variable helium concentrations have been identified in the Ordos Basin through geological exploration. To elucidate the mechanisms underlying the differential helium enrichment in the southwestern Ordos Basin, this study conducted a systematic investigation into the geological settings, hydrocarbon charging histories, and geochemical signatures of three representative areas(C-Area, Q-Area, and L-Area) in this region. The results show that helium concentrations in the C-Area are significantly higher than those in the Q-Area and L-Area. Inorganic geochemical tracers suggest that the C-Area underwent a more pronounced influx of paleo-fluids. Integrated with carbon isotope data, our analysis reveals that natural gases in C-Area and Q-Area are mixtures of coal-derived gas and oil-derived gas with varying proportions, whereas those in L-Area are mixtures of coal-derived gas from different geological periods. Owing to differences in fault systems and hydrocarbon charging histories, compared with Q-Area, the O 2 mj in C-Area experienced intense early-stage hydrocarbon charging. This charging process, accompanied by helium-rich paleofluids migrating upward via basin-scale faults, facilitated the migration of deep helium into the reservoirs. Conversely, the L-Area lacks the requisite hydrocarbon-driven transport effect for deep helium. These differences in hydrocarbon charging and paleofluid migration collectively led to the differential helium enrichment in the southwestern Ordos Basin. • Couple helium accumulation with hydrocarbon gas charging to identify helium enrichment patterns and their differential characteristics. • Comprehensively integrate inorganic and hydrocarbon gas geochemical data with basin evolution, tectonic development to determine helium enrichment in SW Ordos Basin. • Reveals the transport and boosting effect of hydrocarbon gases on helium accumulation; differential charging of such gases in Majiagou Formation, SW Ordos Basin is the main cause of helium's differential enrichment. • Infer fault development and charging process differences cause gas-water relationship variations; both are secondary causes of helium enrichment difference in SW Ordos Basin.