4. Properties of CO2

In order to fully understand CO2-EOR flooding, it is important to look at the properties of CO2 and the fundamentals of the CO2-EOR process. Under ambient conditions, CO2 is a colorless, odorless gas and about 1.5 times heavier than air. CO2 is (2–10 times) more soluble in oil than in the water. CO2 increases the water viscosity and forms carbonate acid, which has a beneficial effect on shale and carbonate rocks [57]. Its properties under standard and critical conditions are summarized in Table 1. Above critical pressures and temperatures, CO2 is in the supercritical state and forms a phase whose density is close to that of a liquid, even though its viscosity


Table 1. Properties of CO2 under standard and critical conditions.

remains quite low (0.05–0.08 cp). This dense CO2phase can extract hydrocarbon components from oil more easily than gaseous CO2 [49].
