Organization
(State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China)
摘要
利用低压氮气吸附法，研究了不同类型黏土矿物孔隙结构特征，在此基础上，利用分子势能理论研究甲烷分子在黏土矿物孔隙中赋存力学机制，揭示了页岩中黏土矿物吸附甲烷的本质。文中从分子间作用力角度出发，利用势能理论建立了单一甲烷分子在孔中相互作用的势能计算模型，即孔径与甲烷分子在孔内位置的双重函数。研究结果表明：甲烷分子越靠近孔壁，势能越大；远离孔壁，势能迅速减小。受到孔壁面势能作用影响的甲烷分子，呈吸附态；未受到影响的，呈游离态。随着孔径增大，甲烷分子受壁面影响区域比例减小，甲烷吸附能力降低。当孔径大于20 nm时，甲烷分子受壁面势能影响区域较小。从微观角度讲，相同孔径中，甲烷分子与黏土矿物间的相互作用力大小顺序依次为高岭石、蒙脱石（伊利石）、绿泥石；从宏观角度讲，黏土矿物样品对甲烷分子的作用力大小的顺序依次为蒙脱石、高岭石、绿泥石、伊利石。
Abstract
In this article, the pore structure characteristics of clay minerals were investigated by the low-pressure N2 adsorption/desorption analysis, and the forces of the methane in the clay mineral pores of shale were analyzed. On this basis, the mechanical mechanics of the methane molecules existed in the shale were investigated by the potential energy theory, revealing the essence of the methane adsorption on the clay minerals in shale. The results show that: from the angle of the intermolecular forces, a model for calculating the interaction potential energy between the methane and the clay minerals was deduced by the potential energy theory, which is the bifunction on the pore size and the position of the methane in pore. The methane molecules affected by the potential energy of the pore walls would form adsorption phase. However, the area far away from the pore walls is not affected by the potential energy of the pore walls and the methane molecules as the free phase is dispersed in the pores. With the increase of the pore size, the affected area by pore wall is decreased and the methane adsorption capacity on the clay minerals decreases. When the pore size is more than 20 nm, the affected area by pore wall is less. From the microcosmic point of view, in the same pore size, the interaction force between the methane and the clay minerals decreases in the following order: kaolinit, montmorillonite, illite, chlorite. However, from a macro point of view, the interaction force between the methane and the clay minerals decreases in the following order: montmorillonite, kaolinit, chlorite, illite.
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