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煤系页岩瓦斯微观解吸机理研究,对煤田区域煤系页岩瓦斯高效安全开采具有重要意义.基于核磁共振(简称NMR)无损检测技术,以典型高瓦斯矿井阜新清河门矿煤系页岩为例,将页岩试样放入低场核磁共振仪夹持器腔体中,通过先吸附,后降低瓦斯压力,模拟煤系页岩瓦斯解吸过程.以核磁共振T2谱幅值积分定量化表征瓦斯解吸量,以核磁共振横向弛豫时间T2均值减小幅度定量化表征煤系页岩孔隙结构收缩变形程度,从微观角度定量研究煤系页岩瓦斯解吸过程中吸附态和游离态瓦斯变化规律.研究结果表明:吸附态和游离态瓦斯核磁共振谱范围可以通过两个横向弛豫时间截止阈值定量划分;吸附态瓦斯量与瓦斯压力符合朗格缪尔等温吸附方程,游离态瓦斯量与瓦斯压力呈线性函数关系;随瓦斯压力降低,煤系页岩微孔隙结构收缩为原孔隙平均半径0.39倍,中-大孔隙结构收缩为原平均孔隙半径0.25倍.
The research on microscopic desorption mechanism of coal-based shale gas is of great significance to the efficient and safe coal mining of shale gas in coalfields.Based on the non-destructive testing technology of nuclear magnetic resonance (NMR), taking the typical coal mine shale of Fuhe Xinhe coal mine in Fuxin, For example, the shale sample is placed in the cavity of the low field nuclear magnetic resonance (MR) holder, the desorption process of coalbed shale gas is simulated by firstly adsorbing and then reducing the gas pressure, and quantitatively characterizing the gas by T2 magnetic resonance spectroscopy Gas desorption amount, the T2 reduction of transverse relaxation time of NMR was used to quantitatively characterize the degree of shrinkage and deformation of the pore structure of coal-bearing shales. From the microscopic point of view, the variation of adsorbed and free-form gas in coal-based shale gas desorption process was quantitatively studied. The results show that the range of adsorbable and free-state gas NMR spectra can be quantitatively divided by two thresholds for the cut-off time of lateral relaxation time. The adsorbed gas and gas pressures are in accordance with the Langmuir isotherm equation. The free-flowing gas quantity is linear with the gas pressure As the gas pressure decreases, the micropore structure of coal-based shale shrinks to 0.39 times the average pore radius and the shrinkage of the mesopore-macropore structure is The original average pore radius 0.25 times.