Centrifuge scaling of supercritical carbon dioxide transport in porous geomaterials

Reliable reduced-scale interpretation of supercritical carbon dioxide migration in saturated porous geomaterials supports the design of geoenvironmental experiments for geological carbon storage. Centrifuge modelling is valuable because it reproduces reservoir-scale transport at reduced laboratory scale while preserving gravity-dependent processes over accelerated prototype-equivalent time scales. Transport results from the coupled action of imposed pressure gradients, buoyancy-driven segregation and molecular diffusion. The similarity treatment of imposed pressure differences, however, is not intrinsically tied to gravity, and existing formulations do not reconcile pressure-driven and buoyancy-driven regimes under a single gravity-controlled time scale. This study develops a physically based scaling framework for coupled Darcy-scale transport that distinguishes similarity regimes by the origin of the driving gradients. A unified implementation is proposed in which the imposed pressure difference is maintained while the pressure gradient scales geometrically with acceleration, so that advection and buoyancy evolve under a common time scale. The framework is verified through reduced-physics simulations at 1, 5 and 10 g. At prototype-equivalent scale, the average saturation histories show a mean absolute difference of about two percentage points between the 1 and 10 g models (linear correlation exceeding 0.998), and the scaled velocity histories depart from the 1 g reference by less than about 5% in the pressure-dominated stage and by up to about 19% near breakthrough.