天然气混源作用对同位素判源的影响

Influence of mixture on isotope indices in gas source discrimination.

同位素参数是判断天然气来源的重要标志，但混源作用能引起这些参数的改变。混源作用能导致甲烷及其同系物碳同位素排列特征（正序，反序）发生部分或全部的变化，这将影响到对生物成因和非生物成因天然气的判别；混源作用以及可能伴随的扩散、分馏作用可引起甲烷、尤其是乙烷碳同位素值的变化，进而影响油型气和煤型气的区分以及混合比的计算。同位素判源的这种局限性在研究混合来源气藏的成因时有必要加以注意。图３表１参７（邓春萍摘）

Mixture of gases from different sources can change the isotope indices which are important markers to determine gas source. Mixture of gases can cause a part or a whole change of carbon isotopic distributive feature in methane and its homologues, including “normal” order or “reverse” order, which would affect the discrimination of a biogenic gas and an abiogenic gas. Mixture of gases along with diffusive fractionation can also change the carbon isotopic value of methane and ethane, thus affect the discrimination of a coal typed gas and an oil typed gas and the calculation of their mixing ratio. Such limitation is notice worthy in the study on the gas origin of a mixed gas pool.