This paper describes the modelling of the main processes for CO2 trapping in saline aquifers, namely solubility trapping, residual gas trapping and mineral trapping. Several important aspects of CO2 storage are presented It has been found that the total amount of CO2 trapped as a soluble component, and as residual gas, can be enhanced by injecting, brine above the CO2 injector. An optimization technique is used to adjust the location and rate of the brine injector to maximize the total amount of CO2 trapping The security of the trapping process is then evaluated by taking into account the leakage of mobile CO2 through the caprock For long-term CO2 storage, the conversion of CO2 into minerals is found to depend on the pie-existing minerals in the aquifer that provide the necessary ions for the reactions to occur