瓦斯压力对煤系页岩瓦斯吸附特性影响核磁共振谱试验研究

瓦斯压力是影响煤系页岩瓦斯吸附特性的关键因素。以阜新高瓦斯矿井清河门矿煤系页岩为研究对象，采用低场核磁共振（NMR）谱技术，通过向放有试样的夹持器中不断充入瓦斯，模拟煤系页岩瓦斯集聚赋存过程。以核磁共振T2谱幅值积分作为反映瓦斯吸附量定量化指标，从微细观角度定量研究瓦斯压力对吸附态和游离态瓦斯量影响规律。试验结果表明，（1）两个截止阈值确定了吸附态和游离态瓦斯T2谱曲线范围；（2）瓦斯压力对煤系页岩吸附态和游离态瓦斯增量均有显著影响。吸附态瓦斯增量变化受控于煤系页岩和瓦斯分子间作用力，而游离态瓦斯增量则主要与煤系页岩孔隙结构有关；（3）吸附态瓦斯量与瓦斯压力间关系符合朗格缪尔等温吸附方程，而游离态瓦斯与瓦斯压力呈3次函数关系；（4）以瓦斯T2谱均值变化幅度定量描述孔隙平均半径扩胀变形程度，随瓦斯压力增加，煤系页岩中～大孔隙结构均发生显著扩胀，平均半径增加1.47倍，而微孔隙结构尺寸未见明显变化。

Experimental study of influence of gas pressure on coal shale gas adsorption characteristics based on nuclear magnetic resonance spectrum

Gas pressure is the major impact factor on gas adsorption of coal shale. Based on the typical high gassy mine, the coal shale of Qinghemen Mine in Fuxin is taken as research object. The sample is placed into the low field Nuclear Magnetic Resonance(NMR) instrument. Through increasing gas pressure, the adsorption process of coal shale gas is simulated. The amplitude integration of T2 spectrum of nuclear magnetic resonance is used as a quantitative index to reflect the gas adsorption capacity. From the micro-quantitative perspective, the influence law of gas pressure on adsorbed gas and free gas is presented. The results show that (1) The ranges of T2 spectrum curve for adsorbed gas and free gas can be determined by the two cutoff thresholds. (2) Gas pressure has significant influence on the increment of adsorbed gas and free gas in coal shale. The incremental change of adsorbed gas is controlled by the interaction force between coal shale and gas molecule. The increment of free gas is mainly related to the pore structure of coal shale. (3) The relationship between adsorbed gas and gas pressure is in accordance with the Langmuir isothermal adsorption equation. The relation between free gas and gas pressure is cubic function. (4) The mean value of gas T2 spectrum is used to quantitatively describe the expansion deformation of the average pore radius. With the increment of gas pressure, the medium- macro pore structures are expanded, and the average radius increases 1.47 times. But the micro-pore structures are not affected.