STUDY ON COAL-BED GAS COMPOSITIONS AND ITS GEOCHEMICAL CHARACTERISTICS IN CHINA

This paper considers, through a lot of measured data of coal-bed gas, that the coal-bed gas is a kind of mixed gas of complex composition with some heavy hydrocarbons. In general, it is not a dry gas. The coal-bed hydrocarbon gases can obviously be divided into three stages of gas-storage: "poor hydrocarbon-storing stage", "rich hydrocarbon-storing stage" and "declining hydrocarbon stage". Authors point out that the normal gas geochemical indexes can relatively well show the geochemical chatacteristics of coal-bed gas. But, "the Benzene Index (B)" is a good indicator to identify the gas original types, and "the Hexane Index(H)" can show the gas evolution law and the organic matter maturity.     

中国煤层烃类气体组份及地球化学特征的研究

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。