基于磁力资料的鄂尔多斯盆地氦气分布规律

Distribution of helium resources in Ordos Basin based on magnetic data

氦气因其独特的化学性质而成为重要的战略资源,中国氦气资源相对贫乏,资源安全形势极其严峻。鄂尔多斯盆地已有一定的氦气显示,但目前对于盆地内天然气中氦气体积分数的认识存在较大差异,对于氦气资源分布规律认识不足,制约了鄂尔多斯盆地氦气资源潜力评价及开发利用。在广泛收集和认识前人研究成果的基础上,以鄂尔多斯盆地磁力异常资料为主,结合347个天然气样品中氦气含量测试结果,分析了鄂尔多斯盆地氦气分布规律。通过对苏里格、庆阳和宜川3个气田天然气样品氦气含量进行测试,发现氦气含量均达到了工业生产的标准(>0.05%),其中庆阳气田Q1区和苏里格气田S47区氦气平均含量超过0.1%。结合岩石磁性特征对磁力异常进行分析,结果表明鄂尔多斯盆地的磁力异常呈明显的分区特征,反映了盆地基底具有多阶段拼合的地质特征,区域性磁力异常变化主要与盆地基底岩性相关,高磁异常条带可能系盆地基底太古界—下元古界深变质的片麻岩、变粒岩、基性火山岩、同期次的花岗岩等强磁性岩体引起;低磁异常主要由板岩、片岩、千枚岩、石英岩、大理岩等弱磁性岩体引起。鄂尔多斯盆地氦气主要为壳源成因,盆地基底下元古界强磁性深变质岩系为鄂尔多斯盆地的氦源岩,盆地中部平凉—庆阳—延安—佳县一带的北东向高磁异常条带为盆地主要的氦气分布区。

Helium has become an important strategic resource because of its unique chemical properties.China's helium resources are relatively poor,and the security situation of helium resources is extremely serious.Helium has been discovered in Ordos Basin,but there are great differences in the understanding of helium volume fraction in the natural gas in the basin and insufficient understanding of the distribution law of helium resources at present,which restricts the potential evaluation and development and utilization of helium resources in the Ordos Basin.In this paper,based on the extensive collection and understanding of previous research results,the distribution of helium in Ordos Basin was analyzed based on magnetic anomaly data and helium content test results of 347 natural gas samples.The helium content of natural gas samples from Sulige,Qingyang and Yichuan gas fields is measured,and it is found that the helium content reaches the industrial level.The average helium content in Qing 1 well block of Qingyang Gas Field and Su 47 well block of Sulige Gas Field is more than 0.1%.We analyzed the magnetic anomaly based on the magnetic characteristics of rocks,and the results indicate that the magnetic anomaly of Ordos Basin have obvious zoning characteristics,reflecting the geological characteristics of multi-stage integration of basin basement.The regional magnetic anomaly variations are mainly related to the lithology of the basin basement,and the high magnetic anomaly bands may be caused by the strong magnetic rock mass such as the archaean-Lower Proterozoic deep metamorphic gneiss,metaggrin,basic volcanic rocks,and the corresponding granites in the basin basement.Low magnetic anomaly is mainly caused by weak magnetic rock mass such as slate,schist,phyllite,quartzite and marble.The helium gas in Ordos Basin is mainly derived from crust,and the deep metamorphic rocks in the lower Proterozoic are the helium source rocks in Ordos Basin.The northeast high magnetic anomaly belt in Pingliang-Qingyang-Yan’an-Jiaxian area in the middle of ordos Basin is the main helium distribution area.