毛细管压力对凝析气体系相态行为的影响

EFFECT OF CAPILLARY PRESSURE ON PHASE BEHAVIOR OF A GAS CONDENSATE SYSTEM

在低渗透多孔介质中 ,由于孔隙半径小而不能忽略毛细管压力对油气体系相平衡的影响。针对这一问题 ,建立了考虑毛细管压力的相平衡计算模型。利用K值多组分模型 (KCOM PVT)软件中的相态模拟计算模块 ,对一个实际凝析气藏中油气体系的毛细管压力、露点压力和恒组成膨胀过程中反凝析液量进行了模拟计算 ,论证了毛细管压力对凝析气体系相平衡的影响程度。计算结果表明 ,润湿性决定毛细管压力对凝析气体系相态行为影响的方式。当润湿角θ为 0～π/2时 ,油气体系的上露点压力上升 ,恒组成膨胀过程中反凝析液量增加 ;当润湿角θ为π/2～π时 ,其变化趋势相反。毛细管半径和界面张力决定毛细管压力对凝析气体系相态行为影响的强弱。只有当毛细管半径低于 10 -5cm时 。

Since the pore radius is very tiny in the low permeability porous media, the capillary pressure should be taken into account. A phase equilibrium calculation model in consideration of the capillary pressure was built. The capillary pressure, dew point pressure and retrograde liquid volume of the constant compositional expansion of a practical gas condensate system were calculated by using this model. The effects of capillary pressure on the phase equilibrium of gas condensate system were discussed. The results show that the affecting mode on the phase equilibrium of gas condensate system is determined by the wettability. The capillary radius and the interfacial tension determine the affecting degree. The upper dew point pressure rises, and the retrograde liquid volume of the constant compositional expansion increases while the wetting angle changes from 0° to 90°. The variation is inversed when the wetting angle is from 90° to 180°. When the capillary radius is below 0.1 micrometers, the effect of the capillary pressure will be obvious.