Disjoining pressure and gas condensate coupling in gas condensate reservoirs

Pore-scale coupled flow of gas and condensate is believed to be the main mechanism for condensate production in low interfacial tension (IFT) gas condensate reservoirs. While coupling enhances condensate flow due to transport of condensate lenses by the gas, it dramatically reduces gas permeability by introducing capillary resistance against gas flow. In this study, a dynamic wetting approach is used to investigate the effect of viscous resistance, IFT and disjoining pressure on pore-scale coupling of gas and condensate. Disjoining pressure arises from van der Waals interactions between gas and solid through thin liquid films, e.g., condensate films on pore walls. Low values of IFT and small pore diameters, as involved in many gas condensate reservoirs, give rise to importance of disjoining pressure. Calculations show that disjoining pressure postpones gas condensate coupling to higher condensate flow fractions-from about 0.08 for vanishing disjoining effect to more than 0.16 for strong disjoining effect. Results also suggest that strong disjoining effect will result in higher gas relative permeability after coupling. Finally, the positive rate effect on gas permeability is only observed when disjoining effects are weak.