Abstract
Matrix-fracture interactions are significant in determining multiphase flow behavior in fractured porous media. We investigated the impact of these interactions on dynamic displacement events and flood-front patterns in a fractured micromodel, with two matrix regions having different permeabilities, of varying wettability states. The effects of injection rate and viscosity were studied during the injection of blank brine and polymer solutions, respectively, under oil-wet (hydrophobic) and water-wet (hydrophilic) conditions. The influence of reducing interfacial tension was examined by injecting a surfactant solution into the oil-wet micromodel. Under oil-wet conditions, brine invaded the high-permeability matrix producing a stepwise increase in water saturation during the low and intermediate rate experiments. The high rate induced fluid displacements within both matrices, but trapped more oil in the high-permeability zone due to what we labeled as the high-rate interruption effect. The stepwise invasion was also observed in the two matrices during the polymer solution injection, contrary to the smoother invasion of the surfactant solution. In the water-wet model, the high-permeability matrix exhibited final fluid saturations resembling those in the oil-wet model after brine injection. However, unlike in the oil-wet model, brine invaded the low-permeability matrix. The polymer solution suppressed trapping and improved the sweep efficiency across the two matrix regions. Our results provide new insights into the pore-scale evolution of fluid saturation during two-phase flow in fractured porous systems under varying wettability conditions.
Published Version
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