Imaging of Water Flow in Porous Media by Magnetic Resonance Imaging Microscopy

Magnetic resonance imaging (MRI) was used to study the flow of water in a column 14 mm in diameter packed with glass beads. The sample was fully saturated and water was pumped through the column using a peristaltic pump, at flow rates of 125 and 250 mL h −1 This corresponds to mean velocities of 0.5 and 1 mm s −1 , given a porosity of 0.46 m 3 m −3 Nuclear magnetic resonance (NMR) images of the proton density and velocities within a 2‐mm slice were taken at a spatial resolution of 0.15 × 0.15 × 2 mm 3 At a mean pore water velocity of 1 mm s −1 we approximated hydrodynamic dispersion using NMR‐measured velocity distributions in a 2‐mm slice through the sample. Additionally, we conducted a step pulse tracer experiment with chloride through the same column and at identical initial and boundary conditions. We fitted the convection–dispersion equation to the breakthrough curve and compared the column scale dispersion of the tracer experiment with the respective NMR estimate derived at the slice scale.