不同海拔地点的空气氩同位素组成特征及其在油气地球化学分析中的意义  

Argon isotopic composition of air at different altitudes and its significance in oil and gas geochemistry

作　　者：李立武 高梓涵 贺坚 曹春辉 李中平 LI Liwu;GAO Zihan;HE Jian;CAO Chunhui;LI Zhongping(Key Laboratory of Petroleum Resource Research,Gansu Province,Northwest Institute of Eco-Environment&Resources,Chinese Academy of Sciences,Lanzhou 730000,China)

机构地区：[1]中国科学院西北生态环境资源研究院,油气资源研究重点实验室,甘肃兰州730000

出　　处：《天然气地球科学》2022年第1期92-100,共9页Natural Gas Geoscience

基　　金：国家自然科学基金(编号:41473062)资助。

摘　　要：氩同位素组成分析在油气成烃成藏地质地球化学研究中获得了广泛的应用。国际上通常采用空气作为氩同位素组成分析的参考气体,因此对空气氩同位素组成的定值研究也一直在进行。但对海拔高度是否影响氩同位素组成还不是很清楚,所以采集了不同海拔(38~5049 m)不同地点的空气样品,用静态真空稀有气体质谱计测量其氩同位素组成。通过多次进样纯化、分离、仪器检测和对结果取平均值的方法,以获得高精度的数据。研究表明,不同地点空气的氩同位素组成有差异,不随海拔高度而单调变化,空气样品的40Ar/36Ar值和38Ar/36Ar值90%的数据分别在298.675±0.995之间和0.18975±0.00245之间,变化范围很小。考虑到天然气40Ar/36Ar值变化范围大,测量不确定性影响因素多,海拔和采样地点因素导致的空气氩同位素组成测量误差对油气成烃成藏研究的影响可以忽略。当天然气40Ar/36Ar值较低时,文中给出了空气干扰的校正公式。Argon isotopic composition analysis has been widely used in the study of geology and geochemistry of hydrocarbon generation and accumulation.In the world,air is usually used as the reference gas for the analysis of argon isotopic composition,so the research on the determination of argon isotopic composition in air has been carried out all the time.It is not clear whether altitude affects argon isotope composition,so air samples from different places at different altitudes(38-5049 m)were collected to measure argon isotope composition by static vacuum noble gas mass spectrometer.Through multiple sample injection,purification,separation,instrument detection and average of the results,high-precision data can be obtained.The results show that the argon isotopic compositions of the air in different places are different and do not change monotonously with altitude.The ratios of 40Ar/36Ar and38Ar/36Ar of the air samples are 90%and 298.675±0.995,respectively and 0.18975±0.00245 respectively,the variation range is very small.Considering the wide variation range of40Ar/36Ar ratio of natural gas,there are many influencing factors of measurement uncertainty,and the influence of measurement error of air argon isotope composition caused by altitude and sampling location on hydrocarbon accumulation research can be ignored.When the40Ar/36Ar ratio of natural gas is low,the correction formula of air interference is given.

关 键 词：稀有气体 标准样品 参考值 重力分馏 Nobless 

分 类 号：TE122.113[石油与天然气工程—油气勘探]