Abstract Understanding fluid transport in microporous media remains a complex challenge due to the intricate interplay of heterogeneity and scale-dependent behaviours. This study introduces a novel multiscale discretisation framework, specifically tailored for dual-porosity systems, and integrates it with an enhanced multiphase solver to determine representative elementary volumes (REVs) across contrasting pore structures. The proposed numerical approach incorporates a hybrid formulation combining two-phase Darcy flow for macro-scale domains with Navier–Stokes and volume-of-fluid (VOF) interface tracking for micro-scale regions. This enables simulation of complex immiscible flows with explicit resolution of both macro- and microporous pathways. A dedicated mesh refinement strategy ensures computational efficiency while preserving geometric fidelity across porosity scales. We apply this framework to two carbonate samples: the Savonnieres carbonate and the Mount Gambier limestone. In the Savonnieres sample, REV convergence could not be achieved even at the largest available micro-CT volume (1000 3 voxels, ~ 3.8 mm 3 ) due to pronounced microstructural clustering. In contrast, the Mount Gambier limestone exhibited stable hydrodynamic and thermodynamic REV behaviour above 1200 3 voxels (~ 3.21 mm 3 ), closely matching experimental core-scale estimates. These findings reinforce the robustness of the proposed methodology and underscore its potential for broader application to microporous media with diverse heterogeneity profiles.
Hussain et al. (Wed,) studied this question.