Molecular understanding of phase behavior of hydrocarbon mixtures in nanopores and their influence on recovery dynamics

• Phase behavior has significant influence on recovery of hydrocarbon mixture from blind nanopores. • Confinement effect can alter the phase behavior of a single component hydrocarbon. • High proportion of methane could inhibit the capillary condensation of octane. • Phase behavior of hydrocarbon mixture is affected by nanopore sizes and the gas-oil ratios. Understanding the phase behavior of hydrocarbons and their mixtures, especially under confinement, is crucial for the extraction of shale oil and gas. In this study, we employed molecular dynamics simulations to investigate the phase behaviors of three typical hydrocarbons (methane, pentane, and octane) in the bulk phase and in nanopores. We find that the confinement effect can alter the phase behavior of a single-component hydrocarbon. For the mixture of methane and octane in nanopores, a rather high proportion of methane could inhibit the capillary condensation of octane. We also studied the influence of phase behavior on the recovery dynamics of hydrocarbon mixtures from blind nanopores of different sizes at different gas-oil ratios. The capillary condensation of the heavy hydrocarbon components in the nanopore throat could hinder the transport of light. These findings increase the understanding of the occurrence states of shale oil and gas and their migration through nanopore throats, providing practical guidance for shale oil and gas development.