Non-hydrocarbon and noble gas geochemistry

Abstract

Isotopic composition of 90 natural gas samples, which were collected from north Jiangsu Province, south Songliao, Sanshui County of Guangdong Province, Sichuan Province, the Junggar and Tarim oil and gas-bearing basins, and the Yaojie coal mine of Gansu Province, have been analysed in terms of δ 13C of CO 2 and CH 4, δD of CH 4, δ 15 N of N 2, 3 He/ 4 He, 40 Ar/ 36 Ar and R/R A . Base on the isotopic and and chemical compositions of the natural gas and the geological background of these areas, such aspects as the genesis of non-hydrocarbon gas, geochemical characteristics of noble gases and the correlation of gases with sources have been discussed. In this paper, it is pointed out that hydrocarbon and non-hydrocarbon gases reservoired in the same stratum may be of different genesis; that the helium of the He-rich gas pool of Huangqiao, north Jiangsu is closely related to the mantle; and that the He and CO 2 of south Songliao, Huangqiao of north Jiangsu, and Sanshui of Guangdong CO 2 pool, have some relationship with the mantle. Like the crust sourced argon, helium also shows the chronological accumulating effect.