基于吸附热理论的煤—甲烷高低温等温吸附线预测

Prediction for Isothermal Adsorption Curve of Coal/CH_4 Based on Adsorption Heat Theory

以高/低温吸附仿真实验装置为依托,选取无烟煤、贫煤和气肥煤等煤阶的系列煤样,通过对高/低温环境(-30℃、20℃、-10℃、-20℃、30℃)煤的瓦斯吸附实验测试,研究不同温度环境煤对甲烷吸附特征曲线的形态特点,同时,采用吸附热理论对高/低温煤的瓦斯等温吸附线进行了预测,研究结果表明:不同变质程度煤的瓦斯吸附量都随温度降低而增大;不同煤质的等量吸附热与等温吸附量呈良好线性关系;利用等量吸附热预测的不同温度下煤的瓦斯等温吸附量与实验结果吻合,误差小于2%。该方法以已知少量等温吸附实验数据,能够准确预测不同温度和压力下煤的甲烷等温吸附能力,这将极大减少实验工作量,并为研究其他温度和压力条件下煤储层吸附性能提供重要依据。

Methane adsorption characteristics in coal play an important role in the gas content estimation and gas productivity prediction in coal-bed,but there are differences of methane adsorption isotherms at different temperatures,so many adsorption isotherms need to test at each temperature,which will cause high cost and long time.According to the metamorphic grade of coal,anthracite coal,lean coal and gas-fat coal were chosen as test coal samples.Gas adsorption tests,which relied on high/low temperature adsorption experiment device,were carried out at 30℃,20℃,-10℃,-20℃ and-30℃ to study anatomic features of methane adsorption characteristic curves.And with adsorption heat theory the gas adsorption isotherms of different coal rank were predicted in the high/low temperature environment.The experimental results show that with the decrease of environmental temperature,the gas adsorption capacity of different coal rank all increase.The isosteric adsorption heat of different coal rank has good linear relationships with the isothermal adsorption quantity.The prediction values of gas adsorption quantity with adsorption heat theory agree well with the experimental results,whose error is less than 2%.With little measured data of isothermal adsorption tests,the method of adsorption heat theory can accurately predict the adsorption ability of coal at different temperature and pressure,which will greatly reduce the workload and provide an important basis to study the coal reservoir adsorption properties.