AN INVESTIGATION INTO WHETHER THE NONDIAGONAL MOBILITY COEFFICIENTS WHICH ARISE IN COUPLED, 2-PHASE FLOW ARE EQUAL

Recent developments in two-phase flow through porous media show that f our mobilities are required to define completely the flow characterist ics of a particular porous medium. Because, in idealized porous media, it has been shown that two of these mobilities, the nondiagonal mobil ities which represent the viscous coupling exerted between fluid phase s, are equal, it has been suggested that they may be equal, as well, i n real porous media. It is shown in this paper that these two interact ive mobilities cannot be equal in real porous media. Moreover, it is d emonstrated that the relative permeabilities which pertain to pure cou ntercurrent flow differ from those which pertain to steady-state, coun tercurrent flow, and that the pure countercurrent-flow relative permea bilities depend strongly on viscosity ratio. Finally, it is suggested that, because three different experiments give rise to three different sets of relative permeability curves, the conventional description of two-phase flow is inadequate inasmuch as it does not account properly for the viscous coupling exerted between fluid phases.