松辽盆地深层天然气资源丰富，在烃类气体成因认识上存在以有机成因为主与以无机成因为主的巨大争议，持无机成因观点者的一个主要论点就是松辽盆地深层天然气的碳同位素发生了倒转。选取松辽盆地深层不同类型有机成因烃类气体和典型的无机成因烃类气体，进行不同成因气体不同比例混合的碳同位素数值模拟，结果发现：不同类型的有机成因烃类气体混合不会产生甲烷及其同系物碳同位素完全倒转，而在不同类型的有机烃类气体中加入一定量的无机成因烃类气体，混合气体中甲烷及其同系物碳同位素都会发生完全倒转。气体混合碳同位素数值模拟结果表明：①松辽盆地深层天然气碳同位素倒转是因为无机气混入的结果;②仅凭天然气负碳系列同位素不能完全断定某种气体为无机成因。

There are abundant natural gas resources in deep formation in the Songliao basin, but there is also a debate between organic origin and inorganic origin of those hydrocarbons. The carbon isotopic reversal of deep gas in the Songliao basin is an important argument of inorganic views. This paper selects several typical organic and inorganic hydrocarbons and makes a numerical simulation through mixing different types of hydrocarbons with different ratios. The results show that: mixing with different types of organic hydrocarbons doesn’t produce a complete carbon isotopic reversal between methane and its homologues, but this complete reversal will happen in mixture of organic and inorganic hydrocarbons. The numerical simulation indicates that: (1) the reason for the carbon isotopic reversal of deep seated gas in the Songliao basin is that some inorganic gas is mixed; (2) only relying on a complete carbon isotopic reversal between methane and its homologues can’t tell which kind of gas is inorganic.