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

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.