Numerical analyses are performed to study the fluid dynamic behaviours of the solubility trapping in the context of CO2 storage in deep geological formations. Dissolution of CO2 into the underlying brine increases the density of brine, leading to a gravitational instability. This instability could give rise to the fingering of CO2-rich brine, which would trigger fluid convection and greatly enhance the dissolution rate of CO2. In light of understanding the three-dimensional (3D) effects on the process as well as the effects of caprock slope, both two-dimensional (2D) and 3D simulations are carried out in this study. For the case with no slope, several differences between the 2D and 3D results are observed in the mass transfer process including the CO2 dissolving rate, although the differences between the results are not obvious at the early stages. The analyses of the 3D results with different grid resolutions show that 3D effects could be important in the convective period while they might be negligible in predicting the onset of convection. For the inclined case, the number of fingers is reduced and the interaction of fingers is weakened with the increase of the inclined angle. The results of inclined cases show a clear directional dependence, indicating that 2D simulations cannot be used for the prediction of the solubility trapping when the caprock has an inclined surface. (C) 2014 Elsevier Ltd. All rights reserved.