力热耦合作用下煤岩吸附及渗透特性的试验研究

Experimental study on the adsorption and permeability characteristics of coal under the coupling of stress and temperature

利用等温吸附试验仪器与含瓦斯煤热-流-固耦合三轴伺服渗流装置,为模拟深部煤层瓦斯开采过程,分别进行不同温度下等温吸附试验与孔隙压力升高的渗流试验,建立考虑过剩吸附量修正的吸附模型并修正吸附膨胀模型,探究力热耦合作用下煤岩吸附与渗流变化规律。结果表明:瓦斯吸附量在不同温度下随瓦斯压力升高均呈增大趋势,随温度升高吸附量逐渐降低。在高压下需考虑过剩吸附量造成的误差,修正的Langmuir模型比原模型计算结果精度更高;建立了考虑温度与过剩吸附量修正的吸附变形模型与吸附膨胀模型,煤岩吸附应变随孔隙压力升高而减小,且温度越高应变变化量越小。随孔隙压力升高,煤岩渗透率及吸附膨胀与滑脱效应导致的渗透率变化量均呈下降的趋势,且随温度升高3者逐渐增加;吸附膨胀是引起煤岩渗透率减小的主要因素,吸附膨胀与滑脱效应对渗透率的贡献率随孔隙压力升高逐渐下降,其贡献率均随温度升高逐渐增加。

In order to simulate the process of gas production in deep coal seams,the isothermal adsorption experiments at different temperatures and the seepage test in the gas loading process were carried out respectively by using the isothermal adsorption device and triaxial servo-controlled seepage equipment for the thermo-fluid-solid coupling of coal containing methane.A modified Langmuir model and adsorption-swelling model considering the effects of excess adsorption were established to investigate the evolution law of adsorption and seepage under the coupling of stress and temperature.The results show as follows:①the gas adsorption volume increases with the increase of gas pressure at different temperatures,while the adsorption volume decreases with increasing temperature.Under high pressure,it is necessary to consider the error caused by excess adsorption capacity.The modified Langmuir model is more accurate than the original model;②the modified adsorption deformation and swelling model considering the correction of temperature and excess adsorption was established.The strain caused by the adsorption of coal gradually decreases with the increase of pore pressure and strain variation decreases with the increase of temperature.With the increase of pore pressure,the permeability of coal and the variable quantity of permeability caused by adsorption swelling and slippage effect show a tendency of decreasing,which gradually increase with increasing temperature;and③adsorption swelling is the main factor that leads to the decrease of permeability of coal.The contribution rate of adsorption swelling and slippage effect to permeability decreases with the increase of pore pressure,and its contribution rate increases with increasing temperature.