川中威远—资阳地区青白口系花岗岩自生自储型氦气成藏特征及潜力分析OA

The helium-rich gas reservoirs that have been discovered so far are mostly developed in the sedimentary cap rocks above basement helium source rocks,while it has not been understood whether self-source and self-reservoir helium gas reservoir can be formed in basement helium source rocks.Based on seismic and drilling data,in combination with experimental analysis of principal and trace elements,SEM and 3D rock CT,this paper studies the source and reservoir characteristics of the Qingbaikou System granite helium in the Weiyuan-Ziyang area of the Central Sichuan Basin,and then establishes a helium accumulation model of self-source and self-reservoir.The following results are obtained.First,this study area is rich in high-quality and effective helium source rocks,with uranium content of 2.68×10-6 to 12.30×10-6,averaging 6.71×10-6,and thorium content of 21.8×10-6 to 49.1×10-6,averaging 32.5×10-6,and it is thick and widely distributed at the basement,generating about 2.20×1011 m3 of helium,which indicates its excellent conditions of helium source supply for strategic resource rich in helium.Second,after high-quality helium source rocks are identified,well-developed micro-and nano-scale pores and microfractures are discovered for the first time in the Qingbaikou System granite in this area,and almond shaped air voids and even vugs can be observed in the field outcrops,which provides conditions for helium migration and storage,enabling the generation and preservation of helium gas in the same formation.Third,based on the combination of geology and seismic,the helium accumulation model of self-source and self-reservoir for the Qingbaikou System granite is established to preliminarily characterize the planar distribution of Qingbaikou System granite.In conclusion,the Weiyuan area of the Central Sichuan Basin is a favorable exploration area of strategic helium resources,for the helium-bearing natural gas in this area is shallowly buried,the favorable zone is large,and there are favorable conditions for large-scale helium enrichment.