A Network Model for Two-Phase Flow in Microfractured Porous Media

摘要

A two-dimensional network model is presented in this paper tornstudy the dynamics of two-phase flow in microfracturedrnporous media. The model here presented is an extension ofrnmodels used in studying fluid flow in intergranular porousrnmedia. The system of microfractures is composed ofrninterconnected orthogonal parallel plates of varying aperturesrnand lengths. Density, length and aperture of the microfracturesrnare randomingly distributed according to distributionsrnreported in the literature for this type of systems.rnFluid flow in each microfracture unit is described by thernparallel plate flow model. The network of microfractures isrninitially satured with a wetting phase and injection of arnnonwetting phase at constant rate and given output pressure isrnestablished. As the drainage process progresses, the fluidsrninterface is tracked in the network: two-phase flowrncalculations are performed in those microfractures containingrnthe fluids interface. Capillary pressure for individualrnmicrofractures is obtained as a function of fracture apperture,rnaccording to a published model.rnRelative permeability curves for the microfracturernnetwork are calculated through flow parameters gathered fromrna representative subregion of the network. The effects ofrnviscosity ratio and capillary number on the characteristics ofrnthese curves are analyzed. The impact of fracture aperture onrnthese properties is also investigated.rnThe necessity for understanding and characterizingrnmultiphase fluid flow in microfractures is driven from a fieldrnapplication recently documented in the literature, for whichrndifferentiation between fluid flow in the small-and large-scalernsecondary porosity media was required. The study herernpresented aims at providing some basic understanding of thernbehavior of multiphase flow in the small-scale secondaryrnporosity-system and its characterization.