页岩中黏土矿物吸附特性分子模拟

Molecular simulations of adsorption characteristics of clay minerals in shale

页岩的吸附解吸特性对页岩气资源开发具有重要意义。为深入了解页岩中黏土矿物微观吸附机理,利用Material Studio分子模拟软件构建了伊利石、蒙脱石和高岭石3种黏土矿物分子模型,采用巨正则Monte Carlo(GCMC)方法对3种模型的等温吸附量和吸附热进行了模拟计算。研究表明,在相同温度和压力条件下3种黏土矿物对CH4分子的吸附量大小顺序是伊利石>蒙脱石>高岭石;随压力增大3种黏土矿物对CH4分子的吸附量均有所增加,而且伊利石和蒙脱石对CH4分子的吸附量对压力变化更为敏感;3种黏土矿物的等量吸附热均小于42 k J·mol-1,对CH4的吸附为物理吸附;随着温度的升高,CH4分子的吸附热和吸附量均减小。

The adsorption and desorption characteristics of shale is very important for the development of shale gas. For the sake of thorough understanding the adsorption mechanism in micro-scale view for clay minerals in the shale, three molecular models including illite, montmorillonite and kaolinite were established by using molecular simulation software Material Studio, the grand canonical Monte Carlo （GCMC） method was used for the calculation of isotherm adsorption capacity and adsorption heat. At the same temperature and pressure, isotherm adsorption capacity of CH4 in three clay minerals was in the sequence below： illite〉montmorillonite〉kaolinite. With the increase of pressure, the isotherm adsorption capacity of CH4 in three clay minerals increased, and CH4 adsorption in illite, montmorillonite was more sensitive to pressure changes than that in kaolinite. The heat of adsorption of three clay minerals were less than 42 kJ · tool-1, proving that adsorption of CH4 was physical adsorption. With the increase of temperature, the adsorption heat of CH4 reduced and the isotherm adsorption capacity of CH4 was decreased, suggesting that high temperature was disadvantageous to adsorption of CH4.