A comprehensive laboratory study was conducted for the recovery of heavy oil from a linear (1-D) and a three-dimensional (3-D) physical models, packed with 12.4 degrees API gravity heavy oil, 60000 ppm brine and crushed limestone. A total of 19 experiments were conducted to investigate the effects of injecting CH4 or CO2 along with steam by using these laboratory models. A linear model having a 6.6-cm diameter and 100-cm length was used for the first group of experiments. In the: second group, a 3-D model with 30-cm x 30-cm x 7.5-cm dimensions was used to obtain the process parameters. Temperature distributions in both models, steam and gas injection pressures, and fluid productions were recorded during the experiments.