On Relative Permeability of Rough-Walled Fractures

Abstract

This paper presents a conceptual and numerical model of multiphase flow in fractures. The void space of real rough-walled rock fractures is conceptualized as a two- dimensional heterogeneous porous medium. characterized by aperture as a function of position in the fracture plane. Portions of a fracture are occupied by wetting and non-wetting phase, respectively. according to local capillary pressure and accessibility criteria. Phase occupancy and permeability are derived by assuming a parallel-plate approximation for suitably small subregions in the frac- ture plane. Wetting and non-wetting phase relative per- meabilities are calculated by numerically simulating sin- gle phase flows separately in the wetted and non-wetted pore spaces. Illustrative examples indicate that relative permeabilities depend sensitively on the nature and range of spatial comlation between apertures.