Network modeling of multiphase flow in fractures

We develop a pore-scale model of wetting in a single fracture. A variable fracture aperture distribution is represented as a square lattice of conceptual pores connected by throats. We borrow concepts from network modeling of flow in porous media to generate a fracture model that includes the effects of flow in wetting layers, snap-off, and cooperative piston-like advance. Cooperative filling accounts for both the curvature of the wetting front in the fracture plane and the effect of the fracture aperture itself. Viscous forces are accounted for using a perturbative method and simulations are performed for horizontal flow, as well as gravity stable and gravity unstable displacements. The wetting phase relative permeability and the trapped non-wetting phase saturation are computed for a fracture whose aperture distribution has been measured using CT scanning. (C) 2001 Elsevier Science Ltd. All rights reserved.