温度与孔隙压力耦合作用下煤岩吸附–渗透率模型研究

为模拟瓦斯抽采过程中温度与孔隙压力对煤岩吸附及渗透特性的影响,利用等温吸附装置、含瓦斯煤热–流–固耦合三轴伺服渗流装置,开展等温吸附试验及不同温度下孔隙压力降低的渗流试验。建立修正的双L吸附模型和考虑温度–孔隙压力耦合作用的煤岩渗透率模型。通过试验结果及试验比对验证其合理性。结果表明:在本文试验条件下,煤岩瓦斯累积解吸量随瓦斯压力降低呈逐渐升高趋势。当温度恒定时,煤岩渗透率在降压过程中呈先降低后升高的趋势。当孔隙压力恒定时,煤岩渗透率在升温过程中呈先降低后升高的趋势。修正后的双L吸附模型比原吸附模型拟合效果更好,能很好反映不同温度下煤岩吸附量与气体压力的变化关系。煤岩瓦斯解吸过程中产生的基质收缩应变随孔隙压力降低而升高。新建渗透率模型与试验数据具有较好的一致性,可以更好的表征不同温度条件下的煤岩渗透率演化规律。

Study on coal adsorption-permeability model under the coupling of temperature and pore pressure

In order to simulate the influence of temperature and pore pressure on the adsorption and permeability characteristics of coal during gas drainage,the isothermal adsorption experiments and the seepage tests in the gas reduce process under different temperatures were carried out respectively by using the isothermal adsorption device and the triaxial servo-controlled seepage equipment for the thermo-fluid-solid coupling of coal containing methane. A modified dual-site L adsorption model was established,and on this basis,a coal permeability model considering the coupling effect of temperature and pore pressure was proposed. The rationality of the new permeability model was verified by test results. The results show that,under the experimental conditions,the cumulative desorption of gas increases with decreasing the gas pressure. The permeability of coal decreases first and then increases with decreasing the pore pressure under a constant temperature. With rising the temperature,the permeability of coal decreases first and then increases under a constant pore pressure. The modified dual-site L adsorption model has better fitting effect than the original model,and can well reflect the relationship between the adsorption capacity of coal and the gas pressure at different temperatures. In the process of gas desorption in coal,the contraction strain of the matrix increases with decreasing the pore pressure. The new permeability model has a good consistency with the test data and can better represent the permeability evolution law under different temperatures.