Immiscible multiphase fluid flows within porous media occur in a range of environmental and engineering applications (e.g. oil recovery, CO2 sequestration, rainfall infiltration, etc). During these processes the bulk fluid front moves quite slow relative to the velocity of the actual fluid interfaces, which advance forward through tortuous pore spaces via rapid "jumps". Recent experiments in ideal systems indicate that after these very rapid fluid displacement events, total system equilibration requires time-frames on the order of several hours; a surprising result heretofore unobserved in geologic samples. These unexepected results raise the possibility that there are fundamental aspects of the physics of fluid interface dynamics that we don’t yet understand. This project aims to isolate one factor (surface roughness) which may contribute to stabilization of fluid-fluid interfaces and thus affect equilibration times.
This project will utilize imaging of fluid interface relaxations, after displacement events, at high temporal and spatial resolution using state-of-the-art 3D X-ray microscopy imaging techniques developed by Applied Maths at ANU. Two experimental porous media systems with the same geometry, but different surface characteristics, will be investigated: (a) a smooth, ideal glass bead pack; and (b) an arbitrarily roughened glass bead pack. Displacement experiments will be conducted and the subsequent relaxation of the fluids will be monitored via 3D x-ray tomography. Quantitative characterisation of time-dependent fluid occupancy (volume), interfacial area, pressure, and curvature will be carried out to establish the differences in equilibration and relaxation time-frames for smooth and roughened surfaces.