Phase equilibrium modeling for confined fluids in nanopores using an association equation of state

Abstract

The conventional cubic‒plus‒association equation of state (CPA EoS) is extended to describe the phase behavior of non‒associating and associating fluids in nanopores. To consider the effects of molecule‒wall interaction, a new pressure term was introduced into the CPA EoS. The modified Laplace equation was used to describe the capillary condensation in confined space. A thermodynamic model, i.e., mCPA/Laplace, based on modified CPA EoS and Laplace equation was presented. Furthermore, while correlations among the tensile strength, fluid critical point, and liquid spinodal point were discussed, the negative pressure for the mCPA/Laplace and mSRK models was studied. The calculations of the mCPA/Laplace model for pure O2, Ar, N2, Kr, CO2, C2H6, C3H8, n‒C4H10, n‒C5H12, n‒C6H14, n‒C7H16 and certain binary mixtures agreed with experimental data. Using the parameter database from the experimental data, this promising study can be extended to both shale oil and shale gas.