A joint model for calculating capillary pressure of confined fluid based on the SWCF-VR equation of state

Abstract

The capillary effect caused by the confinement in porous media leads to strongly differences in the physical properties and phase equilibrium of the fluids apart from the bulk phase. A joint model was established for investigating the capillary effect by combining Young-Laplace equation and the square-well chain-like fluid with variable well-width range (SWCF-VR) equation of state. The Young-Laplace equation supplies a simple way to relate the capillarity with the bulk properties, and the SWCF-VR equation was able to accurately describe the equilibrium of fluid in bulk phase compared with the Peng–Robinson equation. The model could predict well the phase equilibrium when comparing with experimental data in bulk, and consequently the results for confined fluids. The model was verified by experimental and computer simulation data. Further, the binary adjustable parameters of SWCF-VR EOS used in this study could be updated once the experimental data in confined situation are reported. In addition, the model could be used for complex component when experimental data are unavailable since the four parameters of EOS could be predicted.