Abstract:
Helium is an important scarce resource with strategic value, and it plays an irreplaceable role in numerous high-tech and people’s livelihood fields. The accurate measurement of the helium content in natural gas has crucial implication for the correct understanding of the helium resource abundance and scientific evaluation of helium resource scale. The gas chromatography and noble gas isotopic mass spectrometry are commonly used to measure the helium content in natural gas in the laboratory, however, the discussions and understandings on the accuracy and difference of these two methods are weak, which has caused many confusions regarding the sample presentation and the use of data. This work intends to compare the difference and correlation of analytic results of gas chromatography and isotopic mass spectrometry based on the measurements of helium contents in natural gas, and further propose the correction method for the analytical results of gas chromatography. The study indicates that, the mass spectrometry is superior to gas chromatography in terms of accuracy and repeatability, whereas the gas chromatography is economical and fast with simple operation, which is convenient for batch analysis of samples. As affected by the differences on the pretreatment, experimental conditions and procedures, the results measured by the same type of quadrupole mass spectrometry in different laboratories display some differences, which are less than those of the results measured by the gas chromatography in the same laboratory at different times. This suggests that the mass spectrometry has higher accuracy and more reliable results. The helium contents in conventional gas from the oil and gas fields such as Shunbei and Hetianhe in the Tarim Basin and shale gas from Weiyuan gas field in the Sichuan Basin have been measured by both mass spectrometry(
y%) and gas chromatography(
x%) accompanied with the correlation analysis, and the results display favorable linear correlation(
y=1.135 4
x+0.005 7,
R2=0.992 9). This provides new ideas and methods for the scientific and accurate correction of the helium content obtained by gas chromatographic method, and it greatly saves time and economic costs with broad promotion space.