Effect of Interfacial Tension on Relative Permeability Curves Obtained by Considering Surfactant Adsorption and Diffusion

Abstract

To consider the effect of adsorption and diffusion of surfactant on relative permeability, a method for estimating the relative permeability was developed by matching production data obtained through an unsteady-state core flooding experiment and numerical simulation. After the robustness of the method was proven, the necessity of considering surfactant adsorption and diffusion in calculating the relative permeability was proven. Compared with relative permeability curves obtained by neglecting surfactant adsorption and diffusion, the average error of the relative permeability curve obtained by considering surfactant adsorption and diffusion decreases from 11.5% to 3.5% for the oil phase and from 13.1% to 4.2% for the aqueous phase. Finally, the effects of interfacial tension (IFT) on relative permeability curves obtained by considering surfactant adsorption and diffusion were studied. The results show that surfactant adsorption and diffusion affect the relative permeability but not the change in the relative permeability curves for varying IFT. The individual relative permeability curve does straighten with decreasing IFT. As the IFT decreases in a semilog plot, the relative permeability values at the equal-permeability point (i.e., the same relative permeability for oil–water) and residual oil endpoint increase following a logistic function and an exponential function, respectively.