Oscillating Electric Field Effects on Adsorption of the Methane–Water System on Kaolinite Surface

Abstract

A quantitative understanding of oscillating electric field effects on adsorption of the methane−water system on kaolinite surfaces is vital for enhancing methane desorption and forecasting gas production. We have performed nonequilibrium molecular dynamics simulations to investigate the adsorption behaviors of methane−water on the kaolinite (0 0 1) surface applying oscillating electric fields in the frequency range of 0−100 GHz and amplitudes of 0−0.25 V/Å. The simulated results demonstrate that water will preferentially adsorb onto the surface, forming a water layer and preventing the adsorption of methane and thus leading to the reduced adsorption of methane. The applied oscillating electric fields contribute to a thicker water layer and a smaller amount of adsorbed methane for the water−methane system on kaolinite surfaces. Furthermore, higher oscillating frequency and stronger intensity of the applied electric fields facilitate the desorption of methane. These phenomena associate with the fact that the applied oscillating fields reduce hydrogen bond amounts on the interface of kaolinite, and higher frequencies or stronger intensities further break hydrogen bonds. Meanwhile, the interaction energy of water−kaolinite and the self-diffusion coefficient of water increase with the frequency and intensity of the applied electric fields. This study helps us to understand the mechanism of how oscillating electric fields affect the adsorption behaviors of the methane−water system on kaolinite surfaces and is of applicable importance to boost gas production.

In situ study on interactions between hydroxyl groups in kaolinite and re-adsorption water

“…Water obviously affects the desorption behaviors of shale gases from clay minerals. [1][2][3][4] The hydraulic fracturing method could take external water into shale. 5,6 Thus, it would be of practical meaning to study the effect of the interaction between readsorption water and shale on shale gas behaviors.…”

“…Kaolinite, as one of main components in clay minerals, interacts strongly with water through hydrogen bonds. 3,[7][8][9] Ledoux et al 10 summarized the four types of O-H groups in kaolinite, which include two types of outer O-H groups, located on the brokenedge site and on the upper surface of the kaolinite microcrystal structure; the inner-surface O-H groups, which exist on the surface of the octahedral sheets opposite the tetrahedral oxygen; and the inner O-H groups. Different O-H groups have different energies of bonding with water.…”

“…Therefore, a study on the interactions between O-H groups in kaolinite and water would provide fundamental understanding to control the interaction between water and kaolinite in shale, and thus to enhance the amount of methane desorbed from clays. 3,4,11 Previous studies were carried out using D 2 O to investigate the assignment of the O-H groups in kaolinite. 10,[12][13][14][15] However, scant reports use D 2 O instead of water to study the readsorption water behavior in kaolinite.…”

Molecular Simulation of Interactions between High-Molecular-Polymer Flocculation Gel for Oil-Based Drilling Fluid and Clay Minerals

“…The overall characteristics of the kaolinite surface are hydrophilic, with multiple, relatively strong, hydrogen bonds and surface hydroxyl groups on the octahedral surface, and the contact angle of the surface is equal to zero, so the surface has strong hydrophilicity, while the four-sided surface has strong hydrophobicity. There are numerous siloxy groups on the body, and the water molecules on the surface are held together, maintaining the deformed shape of the droplet, indicating that the tetrahedral kaolinite surface is hydrophobic [ 17 , 18 ]. According to the 3D configuration schematics, the interaction between the flocculation gel and electrically neutral surfaces with weak hydrophilicity was relatively weak, but the flocculation gel had good extensibility.…”

Anisotropic Elastic Properties of Montmorillonite With Different Layer Charge Densities and Layer Charge Distributions Through Molecular Dynamic Simulation

“…Figure 6 shows the simulated interaction energy in the MMT layer and the interlayer as a function of layer charge density for the three models. In the three models, the interaction energy in the interlayer all decreases with the increasing layer charge density, indicating enhanced interlayer interactions (Shiu and Tsai, 2014;Wang et al, 2018). The decreasing interlayer interaction energy with increasing layer charge density can be explained by the fact that with increasing layer charge density there are more compensating Na cations in the interlayer that bind stronger the MMT layers (Zhong et al, 2021), resulting in lower interlayer interaction energy.…”