CO₂ flooding is a petroleum-engineering method that injects carbon dioxide to increase oil recovery.
In a CO₂ flood, carbon dioxide is injected into an oil reservoir through dedicated wells. Under suitable pressure and temperature conditions, the gas can mix with or swell the oil, lower its viscosity, and improve the movement of oil toward producing wells. The injected carbon dioxide may be recycled through the field.
CO₂ flooding is a form of enhanced oil recovery, usually applied after primary production and conventional water flooding have extracted much of the easily flowing oil. Its effectiveness depends on reservoir rock, crude composition, pressure, temperature, and the availability of suitable carbon dioxide.
The method is sometimes discussed alongside carbon capture and storage, but the terms are not identical. In some projects, captured industrial carbon dioxide is used for oil recovery and a portion remains underground. That does not automatically mean every CO₂ flood is a permanent storage project.