The distribution of CO₂ is critical to the efficiency and stability of carbon storage; however, the roles of wettability and capillary number in controlling CO₂ distribution remain inadequately understood. In this study, visual waterflooding experiments and numerical simulations were performed using five homogeneous micromodels with distinct wettability characteristics to examine how wettability and capillary number influence CO₂ distribution during short-term waterflooding. The results demonstrate that both wettability and capillary number govern CO₂ distribution patterns and saturation. These patterns include continuous distribution, cluster-like distribution, and isolated bubbles. Both experimental and simulation data reveal that the total residual CO₂ saturation follows a non-monotonic trend with increasing contact angle, while it increases as the capillary number decreases. As the capillary number varies, the displacement behavior transitions gradually from a stable displacement regime to a capillary fingering regime, resulting in variations in residual CO₂ saturation. With changing wettability, cooperative pore filling leads to fluid bypassing, thereby modifying the saturation of continuously distributed CO₂. In contrast, variations in the saturation of cluster-like and isolated bubble CO₂ are attributed to snapoff mechanisms initiated by preceding film flow. This study elucidates how wettability and capillary number govern the residual trapping and distribution of CO₂ at the pore scale.

Fault zones play a key role in controlling subsurface fluid migration, influencing hydrocarbon accumulation, CO₂ sequestration, and geo-energy storage safety. Most previous experimental studies, however, have been restricted to static outcrop or core observations, which fail to capture the progressive evolution of fault zone structures in time as a response to changing stresses. Moreover, existing analogue experiments often use unconsolidated sediments, which cannot accurately represent brittle faulting in consolidated rocks, and quantitative analyses remain limited. To address these challenges, a new method based on ring-shear experiments was developed to physically simulate fault zone formation in consolidated sandstones. The method simulates shear deformation under variable stress and displacement conditions, followed by multi-scale quantitative analyses, including computed tomography imaging, thin section analysis, and porosity-permeability testing under confining pressure. This comprehensive testing routine allows to quantify changes in fault zone thickness, particle and pore size distributions, and grain orientations during progressive deformation and depending on shear parameters. The results demonstrate systematic relationships between effective normal stress, shear displacement, and fault zone structural attributes. The fault zone thickness shows a nonlinear trend with stress, while cataclasis and compaction intensify with increasing displacement. This work provides a methodological foundation for future applications in fault seal analysis, fluid flow modeling, and numerical simulation, offering a practical reference for petroleum systems studies, hydrogeology, and underground gas storage including CO₂ and hydrogen.