Abstract.Flow in porous media is studied at the pore-scale with lattice Boltzmann simulations on pore geometries reconstructed from computed microtomographic images. Pore scale results are analyzed to give quantities such as permeability, porosity and specific surface area at various scales and at various locations.With this, some fundamental issues such as scale dependency and medium variability can be assessed quantitatively. More specifically, the existence and size of the well known concept, representative elementary volume (REV), can be quantified. It is found that the size of an REV varies spatially and depends on the quantity being represented. For heterogeneous media, a better measure may be the so called "statistical REV", which has weaker requirements than does the deterministic REV.

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An experimental approach to study physical processes affecting fluid behavior in three‐fluid porous media systems was designed and implemented. These experiments were designed to provide quantitative evidence of important pore‐scale displacement processes. A unique experimental approach using a two‐dimensional synthetic porous medium (micromodel) and digital image analysis (DIA) enabled both measurement of three‐fluid capillary pressure‐saturation relationships and analysis of fluid behavior at the pore level. Experiments were pressure controlled, and were designed to mimic measurements typically performed on laboratory cores. Only quasi‐static measurements were made, with a focus on capillary pressure‐saturation relations. Different orders of fluid infiltration with respect to wettability were studied. DIA made it possible to obtain quantitative information about the experiments, including fluid saturations, saturation changes between pressure steps, and movement of apparently isolated fluids through films. The results provide insights into important pore‐scale mechanisms and provide a basis for three‐fluid pore‐scale computations.

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