Pore-scale modeling on supercritical CO₂ invasion in 3D micromodel with randomly arranged spherical cross-sections

In this study the delicate invasion nature of pure supercritical carbon dioxide sCO₂, alongside the determination of the main boundaries for sCO₂ flow-pattern transitions inside the nanopores of treated 3D-porous matrix are investigated numerically. Sensitivity parameters under various sCO₂ injection rates and flow regimes are discussed. The numerical outcomes are relied on MRT-Lattice Boltzmann method utilized in this study, while unyielded zones and inactive pores are identified by 3D voxels. The structural complexity of near-spherical porous matrices is addressed to study the flow behaviors of sCO₂. This micrometer media followed a spherical approach with a studied random arrangement. The lengths of the computational domain in transverse directions were set to be five times as long as the highest diameter d_p of the solid matrix, (highest d_p= 50 nm), while the longitudinal direction was set to be 40 times d_p. The simulations are carried out for a wide range of initial sCO₂ velocities, which adimensionally denoted by Reynolds values. As well, unsteady-state flow regimes are adopted for precise interpretations of complex flow patterns and interactions in the nanopores. This numerical methodology allowed the study of the injection boundaries toward each flow regime of sCO₂ inside the complex porous structure. Based on the above analysis, a primary flow-pattern chart is established for the invasion of sCO₂.