我国煤层气组份、碳同位素类型及其成因和意义

本文研究了我国14个煤矿和3口中深井煤层气的组份、甲烷碳同位素组成,发现煤矿煤层气大部分有变干变轻的特征,而中深井煤层气则没有此现象。我国原生带煤层气和从褐煤热模拟成煤作用获得的煤层气亦没有变干变轻。因此认为煤矿煤层气变干变轻是由于受到次生改造的结果。     

COMPOSITION, CARBON ISOTOPE CHARACTERISTICS AND THE ORIGIN OF COAL-BED GASES IN CHINA AND THEIR IMPLICATIONS

The compositions and the carbon isotope characteristics of methanes of the coal-bed gases from 14 coal mines and 3 deep to medium boreholes are studied in this paper.It is found that the coal-bed gases from the coal mines are characterized by the drying or lightening phenomena, which are absent in coal-bed gases from the boreholes.The drying and lightening features were not observed in the coalbed gases derived from both the primary zones and the lignite pyrolysis simulation experiments.Therefore, it is considered that the drying and lightening of coal-bed gases in the coal mines result from the secondary destructive processes.The origins of dried or lightened coal-bed gases may be due to (ⅰ) desorption-diffusion, (ⅱ) the exchange equilibrium of carbon isotopes between CH_4 and CO_2, and (ⅲ) mixing of primary coal-bed gases with syncoalification or postcoalification of biogenetic gases, among which the desorption-diffusion origin is of primary importance.