Interfacial properties of the brine + carbon dioxide + oil + silica system.

Abstract

Molecular dynamics simulations of the H2O + CO2 + aromatic hydrocarbon and H2O + CO2 + benzene + silica (hydrophilic) systems are performed to gain insights into CO2-enhanced oil recovery (EOR) processes. For comparison purposes, an overview of the previous simulation studies of the interfacial properties of the brine + CO2 + alkane + silica system is also presented. In general, the water contact angle (CA) of the H2O + CO2 + silica (hydrophilic) system increased with pressure and decreased with temperature. The CAs of the H2O + hydrocarbon + silica (hydrophilic) system are not significantly affected by temperature and pressure. The simulated CAs were in the ranges of about 58°-77° and 81°-93° for the H2O + hexane + silica (hydrophilic) and the H2O + aromatic hydrocarbon + silica (hydrophilic) systems, respectively. In general, these CAs were not significantly influenced by the addition of CO2. The simulated CAs were in the ranges of about 51.4°-95.0°, 69.1°-86.0°, and 72.0°-87.9° for the brine + CO2 + silica (hydrophilic), brine + hexane + silica (hydrophilic), and brine + CO2 + hexane + silica (hydrophilic) systems, respectively. All these CAs increased with increasing NaCl concentration. The adhesion tension of the brine + silica (hydrophilic) system in the presence of CO2 and/or hexane decreased with increasing salt concentration. The simulated CAs were in the range of about 117°-139° for the H2O + alkane + silica (hydrophobic) system. These CAs are increased by the addition of CO2. At high pressures, the distributions of H2O normal to the silica (hydrophobic) surface in the droplet region of the H2O + silica system were found to be strongly affected by the presence of CO2. These insights might be key for optimizing the performance of the miscible CO2 water-alternating-gas injection schemes widely used for EOR.