在对天然气地球化学特征研究的基础上,对文古2井天然气碳同位素、氦同位素、氩同位素与华北地区煤成气、油型气的这些同位素进行了类比,并结合地质背景综合分析了天然气的成因。指出天然气组成以烃类气体为主,非烃含量低,其中,烃类气体甲烷含量高达93.36%,非烃以CO2为主,含量0.84%;组分中富含重碳同位素,其中甲烷-29.6‰、乙烷-24.3‰、丙烷-21.4‰、丁烷-25.7‰;稀有气体氩同位素比值为1 411.8。通过气源对比认为,文古2井天然气属煤成气,是上古生界煤系源岩在高成熟-过成熟阶段的产物,气藏类型为“自生自储”型。

On the basis of characteristics of geochemistry of Wengu 2 well natural gas, The formation is studied in this paper by using the methods of compare Carbon isotopes, Helium Argon isotopes of  Wengu 2 well natural gas with coal-derived gas and oil-derived gas of Huabei area. The study indicate that: The natural gas of Wengu 2 well are dominated by hydrocarbon, non hydrocarbon content is lower. Methane content is as high as 93.36%, CO₂ content is 0.84%; The δ+{13}C is wighter in components, δ+{13}C-1：-29.6‰, δ+{13}C-2：-24.3‰, δ+{13}C-3：-21.4‰, δ+{13}C-4：-25.7‰; 40Ar/36Ar：1 411.8. The gas and source  rocks  correlation indicate that：The natural gas of Wengu 2 well is coal-derived gas, gas pools type is self generation-self reservoiring gas pools, and from source  rocks of  High mature-over mature period in Upper Palaeozoic.