Modeling carbon dioxide and methane adsorption on illite and calcite: enhancing the simplified local density model through crystal structure modifications

Gang Wu; Xiaofei Fu; Lu Wang; Rui Wang; Binhui Li; Zhejun Pan

doi:10.1039/d3cp05535c

Modeling carbon dioxide and methane adsorption on illite and calcite: enhancing the simplified local density model through crystal structure modifications

Phys Chem Chem Phys. 2024 Feb 28;26(9):7738-7746. doi: 10.1039/d3cp05535c.

Authors

Gang Wu^{1

2}, Xiaofei Fu^{1

3}, Lu Wang^{1

3}, Rui Wang⁴, Binhui Li⁴, Zhejun Pan^{1

3}

Affiliations

¹ National Key Laboratory of Continental Shale Oil, Northeast Petroleum University, Daqing, Heilongjiang 163318, China. zhejun.pan@nepu.edu.cn.
² School of Physics and Electronic Engineering, Northeast Petroleum University, Daqing, Heilongjiang 163318, China.
³ Institute of Unconventional Oil & Gas, Northeast Petroleum University, Daqing Heilongjiang 163318, China.
⁴ National Key Laboratory of Continental Shale Oil, Daqing Oilfield of CNPC, Daqing, Heilongjiang 163002, China.

PMID: 38372654
DOI: 10.1039/d3cp05535c

Abstract

The simplified local density (SLD) model has been frequently utilized to describe gas adsorption in porous media. The common assumptions associated with the SLD model are the graphene slit and uniform distribution of atoms. However, these fail to depict the heterogeneous surface of minerals. In this study, the original SLD model was modified by substituting mineral crystal structures for the homogeneous carbon layer when building the slit. The modified model may capture the heterogeneity-induced variation of the fluid-pore interaction potential and adsorbed phase density near the mineral surface. The calculated adsorption isotherms of methane and carbon dioxide on illite and calcite surfaces at 330.15 K were compared with literature experiment data to validate the modified SLD model. For the simulation of gas adsorption isotherms, the modified model predictions agree reasonably well with the previously reported experiment results using the gravimetric method. The calculated density profile in the slit indicates the monolayer adsorption behavior of CH₄ and CO₂. Based on more precise interaction potentials, the number of regression parameters was reduced to two, and the physical meaning of the model parameters was clarified. Therefore, for estimating hydrocarbon storage in reservoirs, the modified SLD model could be used as an efficient alternative to time-consuming molecular simulation methods.