甲烷在暗色页岩纳米孔隙中微观吸附规律

页岩的吸附能力依赖于其孔隙结构、矿物组成、气体压力及储层温度等。采用蒙特卡洛法，对6种主要页岩成分纳米孔隙中的甲烷吸附行为进行了分子模拟，研究了压力、温度对甲烷吸附量的影响规律，对比了甲烷在有机质、石英、蒙脱石、高岭石、伊利石中的吸附差异，分析了甲烷分子在纳米孔隙中的分布特征和吸附比例。分子模拟结果表明，虽然甲烷吸附量随着温度的升高而线性降低，并随着压力的增大而逐渐提高，但其增加速率会逐渐放缓，其依赖关系可以采用联合的幂函数进行描述。甲烷分子在纳米孔隙中同时表现为吸附态和游离态，吸附态所占比例随着压力的增大而逐渐降低。主要页岩成分的吸附比例存在较大差异，其大小关系为高岭石>伊利石>蒙脱石>有机质（C₅H₄O₂、石墨烯）>石英。

Study on adsorption characteristics of methane in mud shale nanopores by nano-mechanics simulation

The adsorption characteristics of shale gas depend on the pore structure, mineral composition, gas pressure, reservoir temperature and so on. In this paper, the adsorption behaviors of methane in the nano-pores of several main shale components were simulated by Monte Carlo method, and the effects of gas pressure and temperature on methane adsorption were investigated. The methane adsorption in organic matter, quartz, montmorillonite, kaolinite and illite were compared, and the proportion of methane molecules in adsorbed state was discussed. The results show that the adsorption capacity of methane decreases linearly with temperature, and increases nonlinearly with pressure, while the increasing rate of methane adsorption will gradually decrease when pressure is high. The dependence between methane absorption, pressure, and temperature can be described by two combined power functions. Methane molecules in nano-pores display both adsorbed and free states, and the proportion of adsorbed state gradually decreases with pressure. The proportion of adsorbed state in the nano-pore of several main shale components is quite different, and their sequence is kaolinite > illite > montmorillonite > organic matter > quartz.