不同复合页岩模型内气体竞争吸附特性的分子模拟

Molecular simulation on competitive adsorption characteristics of gases in various composite shale models

中文关键词: 页岩气  吸附特性  蒙特卡洛方法  分子动力学

英文关键词: shale gas  adsorption characteristics  Monte Carlo  molecules dynamics

中文摘要:

      构建了高岭石-干酪根IID、蒙脱石-干酪根IID和方解石-干酪根IID三种复合模型,采用巨正则蒙特卡罗方法(GCMC)和分子动力学方法(MD),从分子层面研究了CH₄与注采气体(CO₂、N₂)在复合页岩材料中的吸附情况,分析了不同模型对不同气体的吸附能力。结果表明：在高岭石-干酪根IID复合模型中三种气体的吸附量为：N_CO2＞N_CH4＞N_N2,其中CO₂和CH₄主要吸附于有机质微孔中,N₂主要吸附于片层狭缝中。通过对比三种复合模型的吸附特性等温吸附曲线可以发现：蒙脱石-干酪根IID复合模型对CO₂的吸附量最大,方解石-干酪根IID复合模型对CH₄和N₂的吸附量最大。此外,通过比较无机质与有机质对气体的吸附能力,发现有机质是页岩吸附能力的决定性因素。

英文摘要:

      To better guide the recovery of shale gas, three composite shale models ((kaolinite-kerogen IID, montmorillonite-kerogen IID and calcite-kerogen IID) are constructed in this paper. The giant regular Monte Carlo method (GCMC) and Molecules Dynamics method (MD) are adopted to explore the competitive adsorption characteristics between CH₄ and injection gases (CO₂, N₂) in various composite shale models. The results show that the adsorption capacity of kaolinite-kerogen IID composite model for CO₂, CH₄ and N₂ decreases gradually. Specifically, CO₂ and CH₄ are mainly adsorbed in organic micropores, by contrast N₂ is mainly adsorbed in the interstitial slits. Moreover, the composite shale models present significant effects on the competitive adsorption characteristics. For instance, montmorillonite-kerogen IID composite model has the highest adsorption capacity for CO₂, whereas, the calcite-kerogen IID composite model shows the highest adsorption capacity for CH₄ and N₂. Besides, by analyzing the adsorption capacity of inorganic matter and organic matter for gases, we find that the adsorption capacity of shale is governed by the organic matter.