Helium Enrichment Law and Predication of Prospective Areas of the North Qaidam Basin

Previous investigation and research results show that Dongping and Mabei in the Qaidam basin are helium-rich natural gas fields, and the origin and source of helium have been preliminarily revealed. However, the research on the enrichment law and resource prospect of helium is still weak. In this paper, based on the helium content test of natural gas in Dongping, Mabei and Jianbei gas fields, combined with the previous natural gas composition and rare gas isotope data, the enrichment law of helium in natural gas in the Qaidam basin was studied. The results show that the Qaidam basin has a good prospect of helium gas resources, and the helium content of Dongping 3 well area, Dongping 1 well area, Jianbei gas field and Mabei gas field reaches the standard of industrial utilization. Helium gas is mainly enriched in the basement uplift belt at the plate edge far from the hydrocarbon generating sag, and its content is controlled by the basement lithology; Basement faults and regional unconformity surfaces constitute efficient migration channels for helium and hydrocarbon gas. Pore fissure water, free phase methane and nitrogen are the main carriers of helium migration. Active edge and bottom water promote the migration and enrichment of helium;Gypsum bearing mudstone and thick mudstone with high displacement pressure constitute good preservation conditions. Gypsum bearing mudstone and thick mudstone with high displacement pressure constitute good preservation conditions. Based on the analysis of the controlling factors of helium enrichment, the helium enrichment model of Qaidam basin is established. Based on the analysis of the geological conditions of helium, it is predicted that the Altun mountain front uplift belt and the Mahai Dahonggou uplift belt are the prospective areas of helium resources and the favorable areas for the next helium exploration. The research results can provide directions and clues for the helium exploration in Qaidam Basin.