CO_2/CH_4在干酪根中竞争吸附规律的分子模拟

选取有机质作为研究对象,构建干酪根模型,采用巨正则系综蒙特卡罗(GCMC)方法和分子动力学方法(MD)研究不同摩尔分数、不同压力下CH_4和CO_2的气体的竞争吸附行为以及吸附引起的干酪根本体形变。结果表明:CH_4和CO_2单组分吸附时吸附量随着压力的增大而增大,CO_2吸附会在较小的压力时达到饱和,两种气体吸附符合Langmuir吸附规律,可以使用Langmuir方程进行拟合;在相同的压力和温度下,CO_2/CH_4吸附选择性会随着CO_2摩尔分数的增大而减小,CO_2更易被干酪根吸附;干酪根与CO_2有较强的相互作用,干酪根中不同的原子对吸附起着不同的作用;低压阶段吸附是引起体积应变的主要原因,高压阶段压力对体积应变发挥明显作用。

Molecular simulation of CO2/CH4 competitive adsorption in kerogen

The kerogen model was built and the organic matter was selected as the research object. The CH₄ and CO₂ adsorption behavior and the associated volumetric strain of the kerogen at different CO₂ mole fractions and different pressures were investigated using Monte Carlo (GCMC) and Molecular Dynamic methods. The results show that the adsorption amount of CH₄ and CO₂ increases with pressure increase. And CO₂ adsorption amount can reach maximum at lower pressure. The adsorption of CH₄ and CO₂ accords with the law of Langmuir adsorption and can be fitted by Langmuir equation. The adsorption selectivity of CH₄/CO₂ decreases as the CO₂ mole fractions increase at the same pressure and temperature, and the CO₂ is easier adsorptive by kerogen. Also it is found that there is a strong interaction between kerogen and CO₂, and different atoms play different roles for adsorption in kerogen. At low pressures, the adsorption is the main reasons for volumetric strain, and at high pressures, the pressure is a significant role in volumetric strain.