阳泉矿区寺家庄井田太原组煤层气地球化学特征及成因

Genesis and geochemical characteristics of coalbed methane from Taiyuan Formation in Sijiazhuang mine field of Yangquan mining area

为了研究阳泉矿区寺家庄井田煤层气地球化学特征及成因问题,系统开展了石炭二叠系太原组主力产气煤层(8、9和15煤)煤心样品的现场解吸实验,并收集气样进行组分和碳同位素分析。结果表明:8煤含气量高于9煤,平面上15煤含气量不均匀,部分地区几乎不含气;整个解吸过程中,8煤和9煤气体组分含量及变化规律相近,CH4含量呈先增加后降低、N2含量呈先降低后升高的趋势,而15煤CH4含量呈近线性降低、N2含量呈线性增加趋势;其中,9上煤CH4体积分数为27.82%~76.12%,N2体积分数为21.49%~72.20%,15煤CH4体积分数38.15%~89.41%、N2体积分数为6.55%~61.82%;随着解吸的进行,8煤和9煤中的煤层气碳同位素δ^13C1值总体呈增加的趋势,15煤中的煤层气δ^13C1值总体呈现为3个逐渐增加序列,δ^13C(CH4)与δ^13C(CO2)变化无相关关系。研究区煤层气主要为热成因气,生物作用不明显。另外,关于煤层气组分中CH4含量低异常和N2含量高异常的原因有待进一步研究。

In order to study the geochemical characteristics and the genesis of CBM of Sijiazhuang mine field in Yangquan mining area,the in-site desorption test of coal core samples from the main gas-producing seams(seams 8,9 and 15)from Permo-Carboniferous Taiyuan Formation was carried out systematically,gas samples were collected to conduct component and carbon isotope analysis.The results indicated that the gas content of seam 8 was higher than that of seam 9,on the plan the gas content of seam 15 was uneven,in some parts there was almost no gas.During the whole desorption,the gas component content and the variation regularity of seams 8 and 9 were similar,CH4 content increased firstly and then decreased,N2 content showed the trend of decreasing firstly and then increasing,while the CH4 content of seam 15 showed the trend of nearly linear decline and N2 content showed the trend of linear increase.The CH4 volume fraction of seam 9up was 27.82%~76.12%,N2 volume fraction was 21.49%~72.20%.The CH4 volume fraction of seam 15 was 38.15%~89.41%,the N2 volume fraction was 6.55%~61.82%.With the process of desorption,the carbon isotopeδ^13C1 of seams 8 and 9 showed generally the trend of increase,the overallδ^13C1 of seam 15 appeared as three series of gradual increase.There was no correlation in the variation ofδ^13C(CH4)andδ^13C(CO2).The CBM in the study area was mainly thermogenetic gas without obvious biological action.In addition,for the low CH4 content and high N2 content in the CBM components,further study is needed.