生物气CO2还原途径中碳同位素分馏作用研究及应用

地质历史中,CO2/H2还原产甲烷作用对生物气的形成具有十分重要的意义。中国柴达木盆地第四系生物气主要为CO2/H2还原型生物气。笔者以CO2/H2还原生气理论为指导,进行不同初始碳同位素值和不同赋存状态碳源的生物模拟实验,研究CO2/H2还原产气过程中发生的碳同位素分馏作用。实验结果表明,产物中δ13CH4值与底物的δ13C值呈很好的正相关关系;在反应母质过量的情况下,碳源的赋存状态可以影响产物甲烷的碳同位素组成。以游离形式CO2还原产生的甲烷δ13C值,相对于以HCO3-、CO23-离子形式产生的甲烷δ13C值轻。通过柴达木盆地东部第四系生物气田实例分析,探讨了该区生物气的主要底物CO2的来源及赋存状态,对评价盆地生物气资源和有利勘探区预测有重要的参考价值。

Study and application of carbon isotope fractionation during the reduction process from CO2 to CH4

The CO2 reducted to CH4 pathway is important to biogas generation in the geological history.The Quaternary biogenic gas fields in Qaidam Basin of China belongs to the CO_2/H_2 reduction biogenic gas.According to the theory of H2/CO2 reduction,we have carried out the biosimulation experiments with different occurrences and different initial carbon isotope values of carbon sources.The experimental results indicated that there is a positive correlation between the δ13Cmethane values and the δ13C values of the substrate in products,and that,in response to the existence of excessive substrate,the occurrence of substrate has its effect on the δ13Cmethane values.The δ13Cmethane values from free CO2 reducted to CH4 is relatively lower than that coming from HCO-3 and CO2-3 ions.By applying to the Quaternary biogenic gas filed in the east of Qaidam Basin,the source and occurrences of the main substrate CO2 are discussed,and these have import reference value for evaluating the biogas resources and searching for favorable exploration ares.