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Highresolution X-ray tomography can be used to measure the local mean curvature of fluid–fluid interfaces within the pores of opaque, permeable porous media. Thereof, the pore-scale capillary pressure can be estimated via the Young– Laplace equation. We critically review the aforementioned method by processing experimental data acquired with an X-ray cone-beam laboratory station and compare capillary pressure estimates with results of pore-scale numerical simulations. The method looks promising but is rather sensitive to the attainment of an equilibrium state for the fluid mixture and to the numerical calculation of curvature. Numerical simulation results provide evidence that dynamic effects result in a larger discrepancy between values of the capillary pressure computed from first principles (i.e., pressure difference across the interface) and from geometric considerations (i.e., curvature estimation and Young– Laplace equation).

X-ray radiography is used to sample the moving phase interface in a sequence of water–air and water–oil displacements. A bench-top X-ray CT scanner is used with a still sample continuously flooded with a positive-displacement type pump. A method is proposed to compute two-dimensional instantaneous saturation distributions from the radiographic sequence. Exploitation of the saturation profiles to drive a history-match procedure is demonstrated. This work shows that using simple radiographies of multiphase flows provides a real-time and low-cost method for tracking flooding processes through rock core samples and obtaining relative permeabilities thereof. Most important, due to the much higher frame rate attainable by taking radiographic images, compared to traditional X-ray CT scanning, flows with higher injection rates can be followed.

The experimental investigation of flow through porous media is inherently difficult due to the lack of optical access. The recent developments in the fields of X-ray micro-tomography (micro-CT hereafter), digital sample reconstruction by image-processing techniques and fluid-dynamics simulation, together with the increasing power of super-computers, allow to carry out pore-scale simulations through digitally-reconstructed porous samples. The scientific relevance of pore-scale simulations lies in the possibility of upscaling the pore-level data, yielding volume-averaged quantities useful for practical purposes. One of the best-known examples of upscaling is the calculation of absolute and relative permeability of reservoir rocks. This contribution presents a complete work-flow for setting up pore-scale simulations, starting from the micro-CT of a (in general small) porous sample. Relevant applications are discussed in order to reveal the potential of the proposed methodology.