Distribution of Helium Resources in Weihe Basin, Central China: Insight from 3D Magnetic Inversion

There is promising indication of helium-rich natural gas in Weihe Basin. However, the lack of a detailed investigation on the origin and the spatial distribution of helium source rocks (mainly Yanshanian granites) limits the helium potentiality evaluation in Weihe Basin (WB). We performed three- dimensional (3D) inversions of magnetic data in Weihe Basin and its adjacent areas to figure out the crustal thermal structure and the temporal-spatial distribution of deep granite in the basin. Based on this, we have proposed a geological model of helium accumulation and predicted the potential area of helium distribution. The results of 3D magnetic inversion indicate that the granites in the deep Wei-he Basin are mostly located at the central and southern parts of the basin, which are connected spatially with the granites in the North Qinling Orogenic Belt. These granites were all derived from large-scale intra-continental orogeny in the Qinling area during the mid-Mesozoic, providing a good material basis for crust-derived helium in the basin. The local uplift of the Curie surface makes the thermal fluid more actively, which contributes to helium accumulation. The faults developed in the WB are the migration pathway of crust-derived helium and the upward migration of the mantle-derived helium. The wells with high percentage helium are mostly located near the Weihe fault and the areas on the south of it. The Wugong-Xi’an-Lantian area in the central and the Lintong-Weinan-Tongguan area in the eastern Weihe Basin are the most promising helium distribution areas. Furthermore, the region from the north of Taibai Mountain to Baoji City in the western Weihe Basin may also be another potential area of Helium resource.