Molecular Simulation of Shale Gas Adsorption and Diffusion in Clay Nanopores

Computation

Hongguang Sui²  Jun Yao¹  Lei Zhang²  Qinjun Kang² 

[1] School of Petroleum Engineering, China University of Petroleum, Qingdao, Shandong 266580, China;

关键词: methane;    clay;    adsorption;    molecular simulation;    diffusivity;   

DOI  :  10.3390/computation3040687

来源: mdpi

【 摘 要 】

The present work aims to study the adsorption behavior and dynamical properties of CH₄ in clay slit pore with or without cation exchange structures at sizes of 1.0 nm–4.0 nm using grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) methods. The adsorption isotherms of CH₄ have been investigated by GCMC simulations at different temperatures and various pore sizes. In the montmorillonite (MMT) clays without a cation exchange structure, from the density profile, we find the molecules preferentially adsorb onto the surface, and only an obvious single layer was observed. The general trend within slit pores is that with increasing pore width, the adsorbed amount will increase. However, the larger pores exhibit lower excess density and the smaller pores exhibit higher excess density. The preloaded water will reduce CH₄ sorption. The in plane self-diffusion coefficient of CH₄ which is investigated by MD simulations combined with Einstein fluid equation increases rapidly with the pore size increasing at low pressure. Under these given conditions, the effect of temperature has little influence on the in-plane self-diffusion coefficient. In the MMT clays with cation exchange structure, cation exchange has little effect on CH₄ adsorption and self-diffusion.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.