CO₂ sequestration into saline aquifers can significantly reduce atmospheric greenhouse gas concentrations, making it a key geological carbon storage technology for mitigating climate change and achieving carbon neutrality targets. However, current research predominantly focuses on reservoir saturation states, with limited understanding of dynamic mechanisms at the gas-liquid interface. In this study, microfluidic experiments were conducted at ambient temperature to investigate CO₂ drainage and imbibition under varying capillary numbers, incorporating the remobilization process driven by gas-water interphase mass transfer. Collectively, these three processes determine the temporal distribution of CO₂ and water phase saturations within the porous medium, thereby influencing the efficiency and long-term stability of CO₂ sequestration. With the increase of the capillary number, the sweep efficiency of CO₂ during drainage showed an upward trend, increasing to 54.71%. Moreover, this study provides an in-depth analysis of the distribution and morphological evolution of CO₂ under conditions where the aqueous phase is unsaturated. Results indicate that the asynchronous contraction of cluster interfaces results in a heterogeneous and dynamic dissolution process; the gas-water interface evolution of double-pore ganglia resembles the brine snap-off process; and singlet structures undergo shrinkage and deformation during the dissolution process. These findings elucidate the complex interactions between CO₂-water in porous media and underscore the critical roles of capillary forces and interfacial dynamics in geological carbon sequestration.