Influence of Mineral Types in Nanopores on Carbon Dioxide Oil Displacement Mechanisms

Summary Shale oil, as a strategic resource for future energy security, presents critical technological challenges associated with both efficient extraction and economic viability. However, the microscopic displacement mechanisms remain unclear, necessitating an in-depth investigation at the molecular scale to elucidate the fundamental mechanisms governing shale oil displacement processes and thus provide guidance for practical engineering applications. In this study, nanopore wall models were constructed for four representative mineral types: quartz, kaolinite, calcite, and kerogen. A multicomponent shale oil system was introduced. The dynamic process of carbon dioxide (CO2) displacement of shale oil was systematically simulated based on the classical molecular dynamics method. The analysis focused on oil/rock/gas interaction energies, phase distribution patterns, molecular diffusion characteristics, interfacial force fields, mechanical response of the system, and resulting displacement efficiencies. The simulation results reveal significant differences in the molecular adsorption capacities of the four mineral types. The migration and diffusion behaviors of the oil phase are strongly governed by the surface characteristics of the confining mineral walls. Overall, the displacement efficiencies follow the order of quartz > kaolinite > calcite > kerogen. The results elucidate the microscopic interaction mechanisms among mineral surfaces, pore structures, and oil components during the CO2 displacement of shale oil. These findings provide a solid theoretical basis and scientific guidance for the efficient, economical, and environmentally friendly development of shale oil resources.