On the Accounting of Capillary Forces in the Modeling of Gas-Condensate Mixtures

This article is devoted to the study of the effect of the capillary pressure jump (CPJ) on the phase equilibrium between the liquid and gas phases, which are described by the Peng-Robinson equation of state. A numerical analysis the form of phase diagrams (PD) of a gascondensate mixture at various CPJ is carried out. Based on the specifics of the problem, the PD is constructed in the gas pressure - liquid pressure coordinates. The boundary of the two-phase region is defined as the region of existence of the two-phase state of the mixture, without additional studies on the stability of the single-phase state. The analysis is carried out without reference to any specific porous medium, and it is based on the conditions of phase equilibrium at different CPJ only. The obtained results demonstrate the importance of CPJ effects in computing the phase equilibrium of a gas-condensate mixture, when modeling the flow in a porous medium. The described computational and theoretical technique is applicable to two-phase multicomponent systems with an arbitrary number of components and is easily generalized to other equations of state, such as the Redlich-Kwong equation, equations of state of gas condensate systems.