A two-dimensional network model is presented in this paper to study the dynamics of two-phase flow in microfractured porous media. The model here presented is an extension of models used in studying fluid flow in intergranular porous media. The system of microfractures is composed of interconnected orthogonal parallel plates of varying apertures and lengths. Density, length and aperture of the microfractures are randomingly distributed according to distributions reported in the literature for this type of systems.
Fluid flow in each microfracture unit is described by the parallel plate flow model. The network of microfractures is initially satured with a wetting phase and injection of a nonwetting phase at constant rate and given output pressure is established. As the drainage process progresses, the fluids interface is tracked in the network: two-phase flow calculations are performed in those microfractures containing the fluids interface. Capillary pressure for individual microfractures is obtained as a function of fracture apperture, according to a published model.
Relative permeability curves for the microfracture network are calculated through flow parameters gathered from a representative subregion of the network. The effects of viscosity ratio and capillary number on the characteristics of these curves are analyzed. The impact of fracture aperture on these properties is also investigated.
The necessity for understanding and characterizing multiphase fluid flow in microfractures is driven from a field application recently documented in the literature, for which differentiation between fluid flow in the small-and large-scale secondary porosity media was required. The study here presented aims at providing some basic understanding of the behavior of multiphase flow in the small-scale secondary porosity-system and its characterization.