Capillary and Viscous Fingering in an Etched Network
We present an original set-up for studying the different mechanisms associated with the displacement of immiscible fluids in porous media. A molding technique, using a transparent polyester resin and a photographically etched network has been developed to visualize the front during the displacement. At very low flow-rate we can observe the growth of very thin fingers, even when the displacing fluid is the more viscous. This capillary fingering is very well described by invasion percolation theory and the measured fractal dimension agrees with computer simulations. When the injected fluid is the less viscous fluid, the fingers become more and more dendritic as the flow rate increases; this mechanism seems to be related to a cross-over between invasion percolation and diffusion-limited aggregation (D.L.A.). When the injected fluid is the more viscous fluid, increasing the flow rate decreases the fingering. This mechanism can be described as a cross-over between invasion percolation and a flat interface.
KeywordsPorous Medium Fractal Dimension Capillary Number Viscosity Ratio Immiscible Fluid
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