本文通过对大量煤层气体的实测数据得出:煤层气体是一种组成复杂并含有一定重烃组份的混合气体,在一定条件下它们并非“干气”。煤层烃类气体存在着3个明显的富集阶段,它们分别是煤层烃类气体的贫富集、富富集和衰富集保存期,并与有机质的3个演化阶段相对应。本文指出用常规的气体地球化学指标并不能很好地反映煤层气体的地球化学特征,但“苯指数”能较好地区分出气体的成因类型,“正己烷指数”可以大致反映出气体的演化规律和母质的成熟度。 Based on the measured data of a large amount of coalbed gas, the paper concludes that coalbed gas is a kind of mixed gas with complex composition and heavy hydrocarbon components, and under certain conditions they are not “dry gas”. There are three distinct enrichment stages for hydrocarbon gases in coal seams, which are the enrichment and enrichment, and depletion enrichment, respectively, of hydrocarbon gases in coal seams, corresponding to three evolution stages of organic matter. This paper points out that conventional geochemical indicators do not reflect the geochemical characteristics of coalbed gas well, but “benzene index” can distinguish the genetic type of gas well, and “n-hexane index” can largely reflect the evolution of gas The law and the maturity of the parent material.