Assessment of capillary pressure estimate based on fluid-fluid interface curvature

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).