When oxygen is injected it is primarily converted to carbon dioxide and water. The carbon dioxide has a higher solubility in the oil than flue gas and may even be Miscible. The water generated in the combustion process condenses in the reservoir and displaces oil. Better injectivity than CO2 since all liquid is removed near the well. More water can be injected than with CO2 thereby maintaining high reservoir pressures and favorable phase behavior.
Less gas is produced, offsetting some of the extra investment needed to inject oxygen.
Hydrogen, which has fuel value, is also produced. The following example indicates how oil production benefits. More oil is produced with gas injection than water injection in this low permeability field. Moreover, oxygen injection produces more oil than carbon dioxide injection. Finally, more oil is produced when both water and oxygen are injected, and the project is over many years earlier.