Molecular simulation study on influence of water content on CO2 displacement of CH4 in deep coal seams

作者：ZHANG PANPAN, HAN MINGCHEN, Mu ZongJie, TIAN SHOUCENG, WANG RUI, WEI QILONG, Yin Pengbo · 发表于：DOAJ (DOAJ: Directory of Open Access Journals) · 年份：2026 · 研究领域：Coal Properties and Utilization、Thermochemical Biomass Conversion Processes、Chemical Looping and Thermochemical Processes

To reveal the influence of water content on CO2 injection-enhanced coalbed methane recovery (CO2-ECBM) (CO2 displacement of CH4) in deep coal seams, this study used Fukang deep coal as the research object. Experiments such as 13C nuclear magnetic resonance spectroscopy (13C-NMR) and X-ray photoelectron spectroscopy (XPS) were conducted. A coal matrix model was constructed using molecular simulation software, and the microscopic mechanism of water’s effect on the CO2-ECBM process in deep coal seams was studied using molecular simulation methods. The results showed that after coal matrix adsorbed gas, it underwent significant expansion, and the pore volume significantly decreased. When saturated with adsorbed CH4, the coal matrix porosity decreased by 72.2% compared to the initial value. When the molar ratio of CO2 to CH4 ( xCO2/xCH4 <?fx-imagestate width="10.24466610" height="3.30200005"?> <?fx-imagestate width="10.24466610" height="3.30200005"?> ) was 2, the permeability of coal matrix decreased by 83.8%. Increasing water content significantly inhibited coal reservoir performance. Compared to dry coal, the permeability of the coal matrices with 1%, 3%, and 5% water contents decreased by 50.9%, 94.9%, and 99.6%, respectively, indicating that water strongly hindered gas flow. Competitive adsorption characteristics showed that as xCO2/xCH4 <?fx-imagestate width="10.24466610" height="3.30200005"?> <?fx-imagestate width="10.24466610" height="3.30200005"?> increased, CO2 adsorption...