Pore-Scale Modeling of Multiphase Flow in Fractures and Matrix/Fracture Transfer

摘要

We use pore-scale network modeling to simulate imbibition in fractures and the matrix/fracture interaction. We represent the fracture as a two-dimensional lattice of conceptual pores and throates. We allow flow in connected wetting layers that occupy roughness and crevices in the pore space. We model piston-like advance with a capillary pressure that accounts for the curvature of the meniscus due to the fracture aperture, as well as the curvature of the wetting front in the fracture plane. We show that the model gives results that are insensitive to the resolution or pore spacing of the network. To account for viscous forces, the wetting phase pressure is computed assuming a fixed conductance in wetting layers. This pressure, in combination with the local capilary pressure, is used to determine the displacement sequence. A matrix is incorporated by surrounding the twodimensional fracture plane by a three-dimensional network of pores and throats. We model multiphase flow in a real fracture using an aperture distribution obtained from CT scanning. The simulated saturation distributions agree with those measured using in situ imaging. We also study the matrix/fracture transfer in a large three-dimensional network.