Scaling criteria have been developed and validated to evaluate performance of waterflooding and immiscible CO2 flooding in heavy oil reservoirs by using a three-dimensional (3D) sandpacked displacement model. Experimentally, the 3D physical model consisting of a pair of horizontal wells together with five vertical wells is used to conduct waterflooding and immiscible CO2 flooding processes, respectively. Theoretically, mathematical formulae have been developed for waterflooding and immiscible CO2 flooding by performing dimensional and inspectional analyses. The scaling group of the gravitational force to viscous force is found to be negligible when scaling up a model to its prototype. The relaxed scaling criteria are validated by comparing the simulation results of a synthetic reservoir with experimental measurements and then extended for a field application. There also exists a reasonably good agreement between the laboratory measurements and the field application with the determined scaling criteria.