Preliminary Study On the Controlling Effect of Tectono-Thermal Evolution on Helium-Rich Natural Gas Enrichment in Ordos Basin

Among the numerous gas fields in the Ordos Basin, only a few gas fields such as Dongsheng Gas Field have the potential for helium gas resources, indicating that there are certain differences in the enrichment process of natural gas and helium, and temperature is very important for the enrichment of both gases. This article explores the relationship between natural gas accumulation and helium enrichment from the perspective of basin tectonic thermal evolution. By analyzing the helium source minerals and their helium sealing temperatures in the basement of the Ordos Basin, combined with the tectonic and thermal evolution history of the basin, this study analyzes the distribution of hydrocarbon source rocks and helium source minerals, as well as the spatiotemporal characteristics of natural gas generation and helium release, and discusses the enrichment process of natural gas and helium. The results show that the upper Paleozoic hydrocarbon source rocks in the Ordos Basin are mainly distributed and shallowly buried, and the helium source minerals are mainly zircon, monazite and apatite, which are dispersed and deeply buried. The temperature and time coincidence of the gas gas in the source rocks and the helium released by the main helium source minerals are high, and the enrichment process of the two has a spatio-temporal coupling relationship. In addition, due to the large and concentrated amount of natural gas generated and small and dispersed amount of helium released, it is difficult to enrich helium in the primary gas reservoir near the settlement center of the source rock, while the secondary gas reservoir far from the settlement center of the source rock and near the base of the helium source is often conducive to the rich and integrated accumulation of helium gas. In this study, structural thermal evolution is combined with natural gas rich accumulation and helium release, which opens up new ideas and has certain significance for improving the helium resource investigation and evaluation system.