鄂尔多斯盆地东缘韩城地区煤层气地球化学特征及其成因

鄂尔多斯盆地东缘韩城地区虽是我国第二个大规模投入商业开发的煤层气区，但对其煤层气的地化特征和成因还未形成系统认识。为此，采集了该区井口排采气、煤样、钻井煤心解吸气样和井口排采水共78件样品，并对样品进行了组分、稳定碳同位素等系列分析。实验数据表明，该区煤层气具有以下特征：石炭-二叠系煤层气组成以CH₄为主，重烃和CO₂含量很低，气体湿度（C₂⁺）介于0.014%~2.880%；甲烷碳同位素值（δ¹³C₁）分布范围小，介于-42.978‰~-32.200‰，随深度的增加而变大，与R_o呈正相关关系；乙烷碳同位素值（δ¹³C₂）介于-21.619‰~-9.751‰。δ¹³C₁偏轻、δ¹³C₂偏重：可能是受解吸-扩散过程中同位素分馏作用的影响而造成δ¹³C₁变轻的。最后，根据该区煤层气的演化过程，结合Whiticar图版，综合分析认为该区煤层气成因类型以热降解气为主，且系经过解吸-扩散同位素分馏效应改造的次生热成因气。

Origins and geochemical characteristics of coalbed methane in Hancheng,Eastern Ordos Basin

Although another domestic biggest coalbed methane gas field was put into commercial production in the Hancheng area,western Ordos Basin,there is still no consensus on the geochemical characteristics and origins of the coalbed methane in this field.A total of 78 samples collected from the central and southern parts of this field include wellhead produced gas samples,coal samples,desorption gas samples from coal cores,and wellhead produced water samples,by which gas compositions and stable carbon isotope anal...