First ever reported mechanistic benefits of production strategy on CO2-assisted gravity drainage EOR method through reservoir simulations. Effects of well patterns (vertical injection / horizontal production wells) and type of gas injection wells were investigated using fully compositional 3D reservoir model. Key operational characteristics were identified through monitoring the CO2 floodfront / its breakthrough, oil production rate and respective GOR behaviour, reservoir pressure to satisfy the fundamental Cardwell Parson’s criteria. Other supporting mechanisms (swelling, extraction/ vaporization) were reported at the selective block level. This paper exemplifies the key operational mechanisms supported by fundamental theories. These are first extensive research results based on the reservoir simulations.