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深部低阶煤瓦斯吸附特性核磁共振试验研究

Nuclear magnetic resonance experimental study on gas adsorptioncharacteristics of deep low rank coal

  • 摘要: 为了研究深部低阶煤瓦斯吸附特性,采集新疆艾维尔沟矿深部低阶煤样,采用低场核磁共振技术(NMR)对原煤煤样进行瓦斯吸附试验,并提出了以核磁共振T2(横向弛豫)谱积分面积值作为吸附瓦斯含量的定量表征。试验结果表明:深部低阶煤瓦斯吸附过程T2谱曲线有3个特征峰(吸附峰、游离峰、自由态瓦斯峰);不同瓦斯压力下,瓦斯吸附总量均随吸附时间的增加而增加,直至保持不变,瓦斯吸附速度先增加后减小;不同瓦斯压力下,深部低阶煤吸附孔的瓦斯吸附量随着吸附时间的增加先增加后保持不变,吸附态瓦斯量与瓦斯压力的关系呈双曲线函数分布,瓦斯压力越大,低阶煤中瓦斯达到吸附平衡时间越长。研究成果对深部低阶煤的煤层气勘探开发和瓦斯抽采具有重要指导意义。

     

    Abstract: This paper presents the results of a gas adsorption experimental study on adsorption characteristics of deep low rank coal gas using low field nuclear magnetic resonance (NMR) technique. The coal samples used in the experiment are low rank coal collected from the Aiweigou mine in Xinjiang. The spectral integral area (dimensionless) of the nuclear magnetic resonance T2 (transverse) is used to quantify the adsorbed gas contents. The experimental results show that there are three characteristic peaks (adsorption peak, free peak, and free gas peak) in the T2 spectrum of deep low rank coal gas adsorption process. Under different gas pressures, both total gas adsorption and gas adsorption capacity increase as the adsorption time increases at the beginning and then remain stable. The gas adsorption rate increases at beginning and then decreases with the increases of adsorption time. The adsorption gas volume correlates with the gas pressure by a hyperbolic function. The higher gas pressure is associated with longer time for the gas in the low rank coal to reach adsorption equilibrium. This research provides an important guidance to exploration and development of deep low rank coalbed methane and gas drainage.

     

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