氦气是国防军工和高科技产业发展不可或缺的稀有战略性资源。我国氦气资源匮乏，对外依存度达98%以上。基于鄂尔多斯盆地东缘石西区块25口井81个天然气样分析资料，发现氦气浓度为0.02%~0.23%，平均值为0.089％，具备潜在利用价值。石西区块内天然气氦稳定同位素组成（3He/4He）为0.02×10-6~0.05×10-6，R/Ra（(3He/4He)样品/(3He/4He)大气）值为0.01~0.08，属于典型的壳源氦。石西区块位于离石鼻状构造带，区块东部柳林尖家沟发育燕山期金伯利岩带（B.P.180~100 Ma），该岩带之北百余公里发育与其同源的燕山期紫金山碱性岩体 (B.P.158~130.4 Ma)。航磁异常图显示，石西区块位于北东向展布的正磁异常带边缘。这些地质背景条件表明，石西区块内氦气的来源可能与尖家沟－紫金山岩体深部放射性元素衰变生气有关，该区东部离石断裂带可能提供了氦气运移的主要通道，区内多套储盖层组合为氦气提供了良好的保存条件。石西区块含氦天然气的发现及关于其地质成因的认识，表明鄂尔多斯盆地在适宜的地质条件下可能形成富氦天然气，为该盆地富氦天然气资源进一步调查提供了新的依据。

Helium is a kind of rare and strategic resources for national defense industry and global high-technology applicati ons.However,the helium resource in China is short and the dependence on imported helium exceeds 98%.Based on analysis of the 81 gas samples from 25 wells in Shixi area,the helium volume contents range from 0.02~0.23%,with average of 0.089%.3He/4He ratios are 0.02×10-6~0.05×10-6 and R/Ra ((3He/4He)sample/(3He/4He)atmospheric) values are 0.01~0.08,implying that helium in this area is typically of crustal origin.Shixi area is located in the Lishi nose structural belt.The Yanshanian Kimberlite belt (B.P.180~110 Ma) in Liulin Jianjiagou is situated at the east of Shixi area,and the Zijinshan alkaline (B.P.158~130.4 Ma) rock is located in hundred miles north of Kimberlite belt.In mapping the aero-magnetic anomaly,Shixi area is located in the range of positive aeromagnetic anomalies belt.Thus,the helium of Shixi area may associate with the Jianjiagou-Zijinshan complex,the transcrust/crust deep fault have provided passage for helium gas,and the multilayer deposition strata is the excellent trap conditions.Therefore,a helium-rich gas enrichment area maybe formed in the Ordos basin owing to specific geological conditions.This finding is important for the further evaluation and development of the resource.

1 地质背景

2 样品及测试结果

  2.1 气样采集

  2.2 气样中氦体积分数

3 氦气成因与来源探讨

  3.1 氦气成因

  3.2 氦气来源

  3.3 氦气聚集与保存条件

4 结论