Phase Transition Mechanisms of Hydrocarbons in Nanopores of Shale Formation

To gain a deep understanding of the phase transition mechanisms of confined hydrocarbons, we first use the molecular dynamics simulations to model the phase transition process of hydrocarbons induced by temperature changes. The results show that the phase transition rates of confined hydrocarbons vary at different locations due to heterogeneous strength exerted by pore walls, which enables pure hydrocarbons to exhibit a multiphase coexistence state within the nanopores. Then, Grand Canonical Monte Carlo simulations were preformed to study the pore size effect and interfacial effect of n-pentane in nanopores. The pore size effect primarily influences the volume fraction of the adsorbed phase, while the interfacial effect regulates the density of the adsorption layers. This research provides theoretical insights into the phase behavior characteristic and phase transition mechanism of hydrocarbons in nanopores, which is significant for improving the recovery of shale oil and gas resources.