Oil recovery with water containing carbonate salt, CO.sub.2, and surfactant
AssigneeShell Oil Company
InventorAndrew H. Falls
Life of this patent
Estimating the term…
Abstract
In displacing oil by injecting CO.sub.2, water and surfactant at high pressure, surfactant loss by adsorption is reduced by including alkali metal carbonate or bicarbonate salt in the injected water to increase the pH of the solution at the conditions encountered in the reservoir.
Claims9
In an oil recovery process in which CO.sub.2, aqueous liquid and a preferentially water-soluble, anionic surfactant are injected into a subterranean reservoir to displace oil toward a production location at an injection pressure and rate of fluid production such that the CO.sub.2 is pressurized to at least more than the fluid pressure in the reservoir, an improvement for reducing the extent to which the surfactant is absorbed on the reservoir rocks, comprising:
- including within the aqueous phase of said injected fluid an amount of monovalent cationic carbonic acid salt which is effective for increasing the pH of the solution at the conditions within the reservoir to an extent which reduces the level of the adsorption of the surfactant.
In an oil recovery process in which CO.sub.2, aqueous liquid, and a preferentially water soluble, anionic surfactant are injected into a subterranean reservoir to displace oil toward a production location at an injection pressure and rate of fluid production such that the CO.sub.2 is pressurized to at least more than the fluid pressure in the reservoir, an improvement for reducing the extent to which the surfactant is absorbed on the reservoir rocks, comprising:
- including within the aqueous phase of said injected fluid an amount of sodium bicarbonate which is effective for increasing the pH of the solution at the conditions within the reservoir to an extent which reduces the level of the absorption of the surfactant.
Dependencies are inferred from the claim text.