相对渗透率与含水饱和度关系微观机理

Microscopic Mechanism of Relationship between Relative Permeability Ratio and Fluid Saturation in Porous Medium

经验表明大多数岩石的相对渗透率随饱和度变化曲线具有中间段为直线但两端弯曲的特征。然而,目前对于相对渗透率比值变化规律的微观机理及原因不清楚。岩石多孔介质可以认为由一束束弯曲毛细管束组成,因此岩石多孔介质渗流规律是毛细管孔隙微观渗流的宏观反映。基于毛细管孔隙的两相渗流规律,在毛细管两相流流型分析基础上,研究了毛细管不同流态的微观渗流机理,建立了相对渗透率比值和流体饱和度关系的微观机理模型,从理论上阐述了岩石相对渗透率比值随流体饱和度变化的微观机理。研究表明:相对渗透率变化的微观机理模型与多孔介质渗流的经验规律相一致;液滴流及环状流分别导致了相对渗透率曲线的上翘及下翘;弹状流流态下相对渗透率变化的微观模型与经验公式拟合曲线基本一致;弹状流是曲线出现直线规律的根本原因,也是经验公式的理论基础。

The empirical rule show that the relative permeability ratio curve is characterized by a straight line in the middle,and bending at both ends in most rocks. However,the microscopic mechanism of relative permeability ratio varies with saturation is not clear at present. Based on the two phase flow law and flow state of capillary,the microscopic percolation mechanism of different flow patterns is studied. Then,the microscopic mechanism model of the relationship between the relative permeability ratio and the fluid saturation is established,and the micro mechanism of the relative permeability ratio with the fluid saturation is explained in theory. Research shows that the microscopic mechanism model is consistent with the rule of empirical rule in porous media. Droplet flow and annular flow cause the curve to be upwarped or downwarped. The curve of the theoretical model of the slug flow is basically consistent with the fitting curve of the empirical formula. Slug flow is the fundamental reason for the emergence of straight lines in curve,and is also the theoretical basis of empirical formula.