多孔介质毛细凝聚对凝析气藏露点的影响研究

摘要

凝析气藏流体处于地下多孔介质中，由于多孔介质孔隙壁面的影响，毛细凝聚现象必然存在，从而不可避免地会对反凝析过程产生影响，以致影响凝析气藏的露点。为此，文章在分析毛细凝聚对凝析气藏露点影响机理的基础上，结合流体相平衡的基本理论，建立了考虑多孔介质毛细凝聚影响的凝析油气体系露点预测的相平衡计算数学模型，并结合实例计算分析研究了储层孔隙半径、润湿性等对露点的影响程度。结果表明，亲油岩石毛细凝聚使露点上升，憎油岩石毛细凝聚使露点下降；当润湿性相同时，毛管半径越小，露点所受影响的程度越大；当孔隙半径大于5×10-6cm时,毛细凝聚对凝析气藏露点的影响程度很小，而当小于5×10-6cm时，露点所受的影响较明显。最后得出结论，对于高孔渗型储层，将毛细凝聚的影响忽略不会影响到相平衡理论的准确性；但对于低渗透气藏，毛细凝聚则对露点有较明显的影响作用，在实际工程应用中，应当考虑。%The fluids in condensate gas reservoir are set in subsurface porous media and a capillary agglomerating phenomenon occurs inevitably owing to the effect of pore wall surface in porous media,thus influencing the retrograde condensate process and the dew point of condensate gas reservoir unavoidably.For this reason,in the paper,on the basis of analyzing the mechanism of the influence of capillary agglomeration on the dew point of condensate gas reservoir,a phase equilibrium calculation mathematical model of predicting the dew point of condensate-gas system in consideration of the effect of the capillary agglomeration in porous media is set up in combination with the fundamental theory of phase equilibrium,and the degree of influence of the pore radius and wettability,of reservoir on the dew point is analyzed and researched by calculating a case.It is indicated that the capillary agglomeration in hydrophobic rocks can make the dew point increase and the one in hydrophilic rocks decrease;under the same wettability,the smaller the capillary radius,the greater the degree of influence on the dew point;and when pore radius is more than 5×10-6cm,the degree of effect of capillary agglomeration on the dew point of condensate gas reservoir is very small;when less than 5×10-6cm,the effect on the dew point is relatively obvious.Finally,it is concluded that for the high porosity and high permeability reservoir,when the effect of capillary agglomeration is eliminated the accuracy of phase equilibrium theory can't be influenced;however,for the gas reservoir with low permeability,the effect of capillary agglomeration on the dew point is relatively obvious,which should be considered in the practical engineering.