同位素质谱法测定天然气中He含量及其同位素组成

Analysis of Helium Abundance and Isotope Composition in Natural Gas by Isotopic Mass Spectrometry

将自行研制的天然气中稀有气体纯化浓缩装置与稀有气体同位素质谱仪联机使用,保持样品与空气标准分析流程的一致性,依据峰高比法,测定天然气中He含量及其同位素组成。采集无锡惠山山顶空气作为实验室工作标样,进行不同进样量多次分析,He的浓度及同位素比值测试结果与空气中He的国际公认值吻合,相对标准偏差分别为2.9%、5%,该系统具有较好的准确度和重现性。通过实验室间样品比对,本实验所用的nobless型质谱仪的测试结果相对VG5400质谱仪的分析数据存在一定的系统偏差,但在误差允许范围内。应用该方法分析了塔河油田部分天然气样品,结果表明,He的浓度和同位素组成分析相结合,能够有效的反映油气运聚的特征。

A noble gas purification and concentrating line designed was coupled to mass spectrometer for the analysis of helium（He） abundance and isotope composition in natural gas.Confirmed the same procedures between air standard and natural gas,the measurement results was calculated by the relative peak height proportion.The air sample from Wuxi Huisan as lab＇s working standard was measured repeatedly with the different sample amount.The analystical results obtain agree well with the recommended value,the relative standard deviation of He content and isotope ratio are 2.9 % and 5 %,respectively.The resuts show that the system has good accuracy and reproducibility.The He isotope ratio achieved by this system is consistent with VG5400 mass spectrometer,deviation is less than 10%.The natural gas in Tahe oilfield is measured by this method,the results show that He isotopic composition and its concentration are effective indicator for the hydrocarbon migration.