摘要
On the basis of the carbon isotopic compositions of methane(CH4) and its homologues and the differences in isotopic values for CH4 and ethane (C2H6) and the correlation and compositional char-acteristics of hydrocarbon gases, the author has proposed a genetic classification of natural gases in the oil-gas zone.They are classified as biogenetic and abiogenetic gases in terms of the types of hydrocarbon-generating precursors (or parent materials) and their thermal evolution stages.Biogenetic gases can also be further divided into two series: biochemical and thermochemical gases,with the lat-ter formed at different evolution stages.Gases generated from type-I and -II1 organic matter are called oil-series gases, those from type-III, coal -series ,and those type -II2,mixture-type gases.Gases generated from two or more than two types of precursors are called mixture-source gases.According to those mentioned above, natural gases from the major oil-gas pools in the Sichuan Basin have been discriminantly analyzed,and the results are concordant with the distribution and de-velopment of hydrocarbon-source rocks as well as with their characteristics, indicating a prospective application.
On the basis of the carbon isotopic compositions of methane (CH_4) and its homologues and the differences in isotopic values for CH_4 and ethane (C_2H_6) and the correlation and compositional char- acteristics of hydrocarbon gases,the author has proposed a genetic classification of natural gases in the oil-gas zone.They are classified as biogenetic and abiogenetic gascs in terms of the types of hydrocarbon-generating precursors (or parent materials) and their thermal evolution stages.Biogenetic gases can aiso be further divided into two series:biochemical and thermochemicai gases,with the lat- ter formed at different evolution stages.Gases generated from type-Ⅰ and -Ⅱ_1 organic matter are called oil-series gases,those fiom type-Ⅲ,coal-series gases,and those from type-Ⅱ_2,mixture-type gases.Gases generated from two or more than two types of precursors are called mixture-source gases. According to those mentioned above,natural gascs from the major oil-gas pools in the Sichuan Basin have been discriminatly analyzed,and the results are concordant with the distribution and de- velopment of hydrocarbon-source rocks as well as with their characteristics,indicating a prospective application.
