Abstract: In the process of exploitation of low permeability condensate gas reservoir, the reservoir deformation will occur with the formation pressure decline; the average pore radius will decrease with the effective stress increase, and the capillary pressure effect will change with the pore radius variation. This paper quantitatively analyzes effect of the reservoir deformation on the average pore radius, develops the phase equilibrium mathematical model considering the effects of both the reservoir deformation and the capillary pressure, and then simulates the dew point pressure and phase behavior of constant composition expansion in a condensate gas reservoir. It is concluded that the effect of capillary pressure on phase behavior in distortional media is greater than that in porous media without distortion; the effects of capillary pressure on liquid phase pressure, retrograde condensed liquid saturation and liquid mole fraction in distortional media should be considered, especially, the effect capillary pressure on liquid phase pressure is prominent and should be considered. This paper also discusses the mechanism of the effect of capillary pressure on gas condensate phase equilibrium process, based on the analysis of the phase behavior and the composition.

Key words: distortion, deformation, medium, capillary pressure, phase state, gas condensate field