Influence of Interfacial Phenomena on the Behavior of Condensate Gas Phase in Low-Permeability and Dense Porous Media

Abstract

Low-permeability and tight condensate gas reservoirs are critically important in gas field development due to their substantial reserves and high economic value. However, retrograde condensation significantly affects oil and gas productivity during development. Understanding the impacts of interfacial phenomena in porous media is crucial for enhancing recovery rates of gas and condensate oil. This study integrates the capillary effect and adsorption into a phase equilibrium model, based on the Peng–Robinson equation of state (PR-EOS), to account for interfacial phenomena. The results indicate that the interfacial phenomena significantly impact the phase behavior of condensate gas. Interfacial effects increased the dew point pressure (P_d) by 0.47 MPa and the maximum condensate oil saturation (S_omax) by 3.95%. Capillary pressure primarily affects fluid phase behavior and mobility, while adsorption influences fluid composition and interfacial tension. When the capillary radius (r) is less than 100 nm, P_d increases rapidly with decreasing r. At a pore radius of 30 nm, P_d and S_omax increased by 1.06 MPa and 5.23%, respectively. Higher heavy component content in the fluids enhances capillary pressure and desorption, leading to increased P_d and S_omax. Ignoring adsorption and capillary effects can adversely affect reservoir development. The established numerical model considering complex adsorption characteristics and capillary pressure is crucial for understanding phase behavior in high-temperature, high-pressure porous media and optimizing development strategies for condensate gas reservoirs.