Effect of Viscosity on Relative Permeability

Abstract

Abstract The mechanism of two-phase flow in porous media has been a subject of wide controversy. One of the properties essential for understanding the dynamic behavior of two phase flow is relative permeability. Relative permeability to a certain phase is defined as the ratio of the effective permeability of that phase to its permeability when it is the only fluid present and flowing. In this research, a theoretical analysis was made to determine the effect of viscosity ratio between the non-wetting and the wetting phase on relative permeability. Experimental work was conducted to test the validity of the derived equations. The experiment was conducted on four natural cores. Four oils were used as the non-wetting phases with a viscosity range of 0.42 to 71.30 cp and two wetting phases with a viscosity range of 0.86 to 0.96 cp. Oil and brine were made to flow simultaneously at various ratios, and relative permeability curves were constructed. A total of eight relative permeability cycles representing eight viscosity ratios were run on each sample. It was found that relative permeability to the nonwetting phase varies with viscosity ratio. The relative effect of this variation on relative permeability values was a function of the sample's single-phase permeability, decreasing with its increase. It was concluded that, for samples of single-phase permeability over 1 darcy, the effect of viscosity ratio could be disregarded, and relative permeability would be, in effect