Effects of moisture, salinity and ethane on the competitive adsorption mechanisms of CH4/CO2 with applications to coalbed reservoirs: A molecular simulation study

Injection of carbon dioxide (CO2) into coal seam gas reservoirs has been considered one the most popular approaches to enhance methane (CH4) production. However, many geological and engineering factors influence efficiency CH4 displacement by CO2. These include depth-induced changes in pressure temperature, accompanied compounds, moisture content, salinity underground water. Thereby, mechanisms adsorption competitive processes between CO2 coalbeds at microscope level remain be explored. In this paper, a hybrid molecular dynamics (MD) grand canonical Monte Carlo (GCMC) method is conducted probe properties behavior 0–5 wt% 0–6 mol/L saline NaCl, C2H6. Gas molecules are undertaken 308, 338, 368 K with up 30 MPa. Effects Moisture, C2H6 effects on characteristics discussed detail. Based simulation results, impedes isotherms, which leads 17.1 % reduction amount 5 content. Moreover, further decreases capacity, drops 6.1 6 NaCl within addition, another negative factor process, reduces 36.6 ethane mentioned preferential selectivity SCO2/CH4 shows also analyzed. Moisture content promotes owing CH4's more sensitivity presence H2O molecules. Furthermore, high hinders solubility water, whereas an inverse characteristic CO2, thereby, improves SCO2/CH4. Besides, developed The observations study have important implications for accurate estimation unconventional resources help