In this study, we investigate CO2-foam injection as a promising technology to increase the security of CO2 sequestration process. To evaluate the performance of CO2-foams in saline aquifers, the Delft Advanced Research Terra Simulator (DARTS) is used to predict CO2-foam dynamic behavior. A consistent thermodynamic model has been implemented in DARTS to describe the phase-behavior of the CO2-brine system with impurities. This phase-behavior module is combined with representation of foams by an implicit-texture (IT) model. An Operator-Based Linearization (OBL) approach is utilized for fully implicit approximation. The OBL approach reduces the nonlinearity of the physical problem by transforming the discretized nonlinear conservation equations into a quasi-linear form based on state-dependent operators. In our work, a small 2D domain with the presence of a capillary transition zone (CTZ) is used to investigate the effect of capillarity on the CO2 dissolution rate at different thermodynamic conditions. Then we use a 3D unstructured reservoir to examine CO2-foams behavior and its effects on CO2 storage. The results show that foam-assisted CO2 injection can reduce gas mobility effectively by trapping gas bubbles and inhibit CO2 from buoyancy-driven migration upward, thus enhancing storage efficiency. At the same time, the CO2 convective dissolution trapping enhanced by the presence of a CTZ is more limited in the CO2-foam scenario comparing to pure CO2 injection. The results of our investigation suggest that CO2-foam co-injection is a promising technology to mitigate risks at short time scales while pure CO2 injection has advantages from a long-term sequestration perspective.