2-PHASE FLOW IN A VARIABLE APERTURE FRACTURE

In this paper a dynamic two-dimensional two-phase flow model for a sin gle variable aperture fracture is developed. The model is based on a f inite volume implementation of the cubic law and the conservation of m ass for each liquid. The two-phase fracture flow system is represented by incompressible parallel plate flow within two-dimensional subregio ns of constant aperture. The fluid phase distribution is represented b y an explicit definition of the phase presence at each location within the domain. To achieve this definition, a phase distribution is assig ned to each fracture subregion. Knowledge of the phase distribution al lows calculation of interface capillary pressure based on the fracture aperture. One-dimensional analytic solutions for two-phase flow are d eveloped and used to verify the model's behavior in one dimension. The model is verified against the Sandia Waste-Isolation Flow and Transpo rt III model for the case of two-dimensional single-phase flow. Two-di mensional two-phase flow verification is performed qualitatively becau se no suitable analytic or physical model is currently available. Two- dimensional flow phenomena are investigated for variable aperture frac tures generated using geostatistical methods. Results from these simul ations illustrate the flow processes of phase isolation, pinching off of nonwetting phase globules, nonwetting phase refusal at the edges of tight regions, and downslope migration of a fluid countercurrent to f low of a less dense fluid.