There is an overwhelming evidence of increased levels of green house gases such as CO2 in the atmosphere with an urgent need to stabilize the CO2 atmospheric content by storage in geological formations. The main concern in geological storage of CO2 is its long term subsurface retention. Primary containment mechanisms are dissolution in water, reaction with rock, and capillary trapping. Development decisions such as number of injection wells, injection rates, well placement, and the need for water production/reinjection may pose a profound effect on long term storage. A reservoir simulation study was conducted to study several injection schemes to assess the impact on the amount sequestered and the extent of vertical migration. Simulations were performed using the compositional reservoir simulator CMG-GEM (2009). Thermal and geomechanical effects were not considered. Several prototype reservoir geomodels were studied to determine the impact of injection strategy on injectivity, CO2 retention, plume extension, and upward movement to formation top seal. It is demonstrated that the well placement, well completion and injection schemes have strong impact on the amount of residual and dissolved CO2. The CO2 injectivity was severely impaired when water and gas are injected simultaneously.