页岩气在Ⅱ型干酪根有机质中吸附的分子模拟
Molecular Simulation of Shale Gas Adsorption onto Ⅱ Kerogen Organic Matter

有机质是页岩气吸附的重要场所， 室内实验描述干酪根有机质的物理和结构性质和研究页岩气在其中的吸附非常困难。 分子模拟软件根据干酪根的实验分析数据构建干酪根有机质模型能在分子水平上研究气体的吸附状态。 通过构建三维的Ⅱ干酪根模型， 运用巨正则蒙特卡洛方法(GCMC)来研究页岩气在干酪根分子模型中吸附， 分析了干酪根类型、 温度、 气体组成对气体吸附的影响和吸附剂模型对CH4, C2H6的选择吸附性。运用分子动力学(MD)方法分析了页岩气在干酪根模型中吸附的结构性质。 结果表明： 相比于Ⅱ-C, Ⅱ-D型干酪根模型有更大的吸附量； 温度升高， 吸附量减小； 在多组份气体吸附中随着压力的上升C2H6吸附量呈现了先增大后减小， 最后趋于稳定的现象； 干酪根模型对C2H6具有优先吸附的性质； 干酪根模型中S原子与气体分子之间的相互作用最强， H原子与气体分子之间的相互作用距离最小。
Organic nodule is an important place for shale gas adsorption. It is difficult to characterize the physical and structural properties of the organic matter and comprehensively analyze the gas adsorption in organic matter by experiment. Molecular simulation software can construct the kerogen organic matter model based on the experimental data and study the adsorption states of the gas at the molecular level. This work utilizes the grand canonical Monte Carlo method (GCMC) to study the shale gas adsorption in kerogen molecular model, the influences of kerogen type, temperature and gas composition on gas adsorption and the selectivity of C2H6 relative to CH4. Molecular dynamics (MD) method is also used to analyze the structure properties of shale gas adsorption in the kerogen model. The results show that Ⅱ-D type kerogen molecular model has alarger adsorption capacity compared with Ⅱ-C. The higher the temperature, the smaller the adsorption quantity. In the case of multi-component gas adsorption, the adsorption quantity of C2H6 increases firstly and then decreases, finally, it becomes stable with the increasing pressure. The kerogen model preferentially adsorbs ethane. The interaction between the sulfur atoms and the gas molecules is strongest. The interaction distance between hydrogen and gas molecules is minimal.