Investigation of the factors influencing methane adsorption on illite

Abstract

The molecular simulation method was used to investigate the adsorption behaviors of methane on illite. The effects of several factors on methane adsorption, free gas amounts, and the proportions of absorbed gas in the illite nanopores, including the pore size, temperature, and water content, are discussed. The results obtained show that methane adsorption in illite nanopores is due mainly to van der Waals adsorption. With an increase in the pressure or of the pore size, the free gas amounts of methane increase, whereas the free gas amounts decrease with increasing temperature or water content. With increasing pressures or decreasing pore sizes, the methane adsorption capacity of the illite pores increases. When the pressure or pore size increases, the proportion of the adsorbed gas in the pores decreases. As the temperature increases, the methane adsorption capacity of the illite pores decreases, and the proportion of adsorbed gas in the illite pores decreases slightly. The adsorbed phase density decreases with increasing pore size and temperature, whereas the adsorbed phase density increases with increasing pressure. The electrostatic forces and hydrogen bonds have a positive effect on water adsorption in the illite nanopores, while the van der Waals forces have the opposite effect, which causes the water molecules in the illite pores to exist in the form of aggregates. The water molecules occupy the areas near the pore walls in a directional manner and occupy the adsorption space and the adsorption sites of methane, resulting in a decrease in the methane adsorption capacity and a slight reduction in the proportion of adsorbed gas. K E Y W O R D Sadsorption capacity, illite, influence factor, methane, proportion of the adsorbed gas 3318 | XIONG et al.

Molecular Dynamics Simulation and Experimental Studies of the Wettability Behaviors of Shales

“…The degree of hydrophilicity or lipophilicity depends on the oxygencontaining functional groups distributed on the surface of organic matter. According to the author's previous research results, 22,23,58,59 the competitive adsorption capacity of water molecules existing in quartz pores, illite pores, and organic matter pores is better than that of methane molecules, which can affect the methane adsorption capacity in nanoscale pores in shales. In organic matter pores, water molecules gather near oxygen-containing functional groups in a directional arrangement, but a certain number of methane molecules are still distributed near the pore wall.…”

Molecular Simulation of Adsorption and Diffusion of Methane and Ethane in Kaolinite Clay under Supercritical Conditions: Effects of Water and Temperature

“…It was found that H 2 O preferentially adsorbs and accumulates on the slit wall and kaolinite shows strong hydrophilicity. Due to the fact that water molecules are polar molecules, there are strong electrostatic forces and van der Waals forces between water molecules and the slit wall, and there are hydrogen bonds between water molecules [15][16][17]. With the increase in the number of water molecules, H 2 O will gradually appear in the middle of the slit and increase with the further increase in the number of H 2 O molecules.…”

“…Li et al [16] suggested that stronger interactions between water molecules and the slit walls (electrostatic forces and van der Waals forces) would occupy more adsorption space leading to a significant decrease in the amount of CH 4 adsorbed in illite, montmorillonite and chlorite. Xiong et al [17] concluded that the electrostatic force between water molecules and the wall and the hydrogen bonding effect between water molecules make it easy for water molecules to accumulate on the surface of minerals to occupy the adsorption space, which is unfavorable for CH 4 adsorption. Huang et al [18,19] in their study found that the occupation of enterable pores by H 2 O in the form of clusters lead to a decrease in the adsorption capacity of CH 4 and CO 2 in casein.…”

Methane/Carbon Dioxide Adsorption and Diffusion Performances at Different Mineral Compositions and Buried Depth Conditions

“…30,31 At the same time, X-ray diffraction (XRD) and total organic carbon (TOC) measurements show that illite, montmorillonite, and calcite are the major components of the clay types in the shale. 32,33 Therefore, based on the above research and the problems to be solved, this paper adopted the molecular simulation method to comparatively analyze the methane and carbon dioxide adsorption and diffusion performances in these three minerals and to explore the influences of different buried depths on their adsorption and diffusion performances.…”

“…Certain achievements have been attained regarding the mechanisms underlying the adsorption and diffusion behaviors of methane; , however, most studies focus on the adsorption and diffusion behaviors of methane in single minerals. In actual practice, shale is usually jointly constituted by multiple minerals with significant differences in the sizes of pores that can store gas, which means that the adsorption capacities of minerals for methane are different. , At the same time, X-ray diffraction (XRD) and total organic carbon (TOC) measurements show that illite, montmorillonite, and calcite are the major components of the clay types in the shale. , Therefore, based on the above research and the problems to be solved, this paper adopted the molecular simulation method to comparatively analyze the methane and carbon dioxide adsorption and diffusion performances in these three minerals and to explore the influences of different buried depths on their adsorption and diffusion performances.…”