Pore level investigation of the effect of viscous coupling, displacement flow rates and porous medium topology on two-phase flow relative permeabilities

One of the most important properties for understanding the multiphase flow in porous media is relative permeability. In two-phase flow, the relative permeability to a given phase is generally assumed to be only a function of its saturation, independent of the properties of fluids involved and/or flow conditions and ranging from zero to one.;Considering the physical principles of multiphase flow through porous media, two capillary models are developed to determine the effect of the viscous coupling on relative permeabilities. Different cross-sectional geometries are analyzed and two-phase flow problems are solved analytically.;Experiments are conducted to confirm the effect of the viscosity ratio and to investigate the effect of the displacement flow rate and porous medium topology on two-phase relative permeabilities. Two different etched-glass micromodels and acrylic-made triangular capillary tubes are used as porous media and different pairs of fluids are used.;Experimental results show that relative permeabilities vary with the viscosity ratio and the injection flow rate. It is also observed that relative permeability to the non-wetting phase may take values larger than unity when viscosity ratio is larger than one. This "lubrication effect" observed in the non-wetting phase seems to be affected by the topology of the porous medium.;Experimental relative permeabilities are compared to those predicted by the capillary models. Good agreement is observed in drainage displacements through the equilateral triangular channels at low Reynolds numbers and annular flow conditions.