The gas assisted gravity drainage process is designed to take advantage of gravity between the injected gas and reservoir crude oil due to the difference in their densities. In this experimental study ,a 2-D Hele-Shaw physical model with dimensions of 15 x 66 x 3 cm was packed with uniform and different sand packs to conduct visual experiments of CO2 injection. These experiments were designed to imitate the dimensionless parameters observed in some field projects. The results show high Bond number lead to high oil recovery because of large absolute permeability. Additionally, the reduction rate of CO2 injection from 50 to 20 cc/min tends to decrease the amount of Capillary number and then increase oil recovery. Comparison between free and forced gravity drainage applying forced gravity drainage was found to be essential with regard to oil recovery.