煤系页岩瓦斯吸附-解吸特性核磁共振实验研究

吸附态和游离态瓦斯变化规律能为煤系页岩瓦斯安全高效抽采提供技术参考，常规实验方法难以实现对吸附态和游离态瓦斯变化规律的独立表征。以阜新盆地清河门矿煤系页岩为例，采用低场核磁共振技术对煤系页岩粉试样进行瓦斯吸附-解吸实验，并提出以核磁共振T2（横向弛豫时间）谱幅值积分作为瓦斯含量定量表征指标。实验表明:吸附-解吸过程T2谱曲线有3个特性峰，对应3个横向弛豫时间截止阈值；吸附态瓦斯量与瓦斯压力符合朗格缪尔方程，而游离态瓦斯量与瓦斯压力呈线性关系；吸附态瓦斯解吸过程具有明显滞后性，且存在7.26 MPa临界滞后瓦斯压力，而游离态瓦斯吸附和解吸过程近似可逆，无明显滞后性。

Experimental research on adsorption-desorption characteristics of shale gas in coal shale by nuclear magnetic resonance

The change laws of adsorbed and free gas can provide some technical reference for safe and high-efficient exploitation of coal shale gas, but the conventional experimental methods are difficult to achieve the independent representation on the change laws of adsorbed and free gas. Taking the coal shale of Qinghemen mine in Fuxin basin as example, the gas adsorption-desorption experiments were carried out on the powder specimens of coal shale by using the low-field nuclear magnetic resonance (LF-NMR) technique, and it was put forward to take the amplitude integral of T2 (transverse relaxation time) spectrum in NMR as the quantitative representation index of gas content. Some new experimental results were obtained as follows. The T2 spectrum curve in the adsorption and desorption process had three characteristic peaks corresponding to three cut-off thresholds of transverse relaxation time. The relation between the adsorbed gas amount and the gas pressure accorded with Langmuir equation, while the free gas amount depended linearly on the gas pressure. The desorption processes of adsorbed gas had an obvious lagging, and the critical lagging gas pressure was 7.26 MPa. However, the adsorption and desorption process of free gas was approximately reversible, without the obvious lagging.