淮南煤田潘北煤矿4-1煤层瓦斯组分和碳同位素特征及其成因意义

摘要

Geochemical characteristics including coal seam gas composition and carbon isotopes are impacted by gas formation process and later transformation thus have significance in differentiation of coal seam gas genesis. Taking the coal No. 4-1 gas samples from Panbei coalmine, Huainan coalfield as subject investigated, carried out tests of gas composition and carbon isotope (CH 4, CO2) values. The result has shown that in coal No.4-1 hydrocarbon gases, methane is absolute predominance, poor heavy hydrocarbon gases;in non-hydrocarbon gases, CO2 content less than 5%, thus present obvious secondary biogenic characteristics. The correlativity between nitro⁃gen content and methane content demonstrated gas composition is largely impacted by atmosphere. Variation range of methane carbon isotopic values in coal No.4-1 is-62.15‰~-51.57‰, combined with coal seam metamorphic stage, figured out its secondary biogen⁃ic gas attribute;while CO2 carbon isotopic characteristics demonstrated the typical biogenesis.%煤层瓦斯组分和碳同位素等地球化学特征受瓦斯形成过程和后期改造作用影响，对判别煤层瓦斯的成因具有重要的意义。以淮南煤田潘北煤矿4-1煤层瓦斯样品为研究对象，分别对气体组分和碳同位素(CH4、CO2)值进行了测试，结果显示：4-1煤层瓦斯烃类气体中甲烷占绝对优势，贫重烃气体，非烃类气体中二氧化碳含量少于5%，呈明显的次生生物成因特征。氮气与甲烷含量之间呈负相关，说明瓦斯组分受大气影响较大。4-1煤层甲烷碳同位素值为-62.15‰～-51.57‰，结合煤层的变质阶段，属于次生生物成因气，二氧化碳碳同位素特征则表明其典型的生物成因。