Foam mixture for steam and carbon dioxide drive oil recovery method

A method for recovering oil from a subterranean, oil-containing formation penetrated by at least one injection well and at least one spaced-apart production well, said wells being in fluid communication with a substantial portion of the formation, comprising:

• (a) injecting steam into the formation and producing fluids including oil from the formation via the production well for a predetermined period of time, thereby forming a steam-swept zone in the formation;
• (b) thereafter injecting a mixture of a noncondensible gas and an aqueous surfactant-starch solution into the formation via the injection well, said surfactant-starch mixture capable of forming a stable foam with residual oil in the steam-swept zone at formation conditions of temperature and pressure thereby significantly decreasing the permeability of that zone and diverting the steam, non-condensible gas, into other portions of the formation;
• and
• (c) injecting steam into the injection well and recovering fluids including oil from the formation via the production well.

A method for recovering oil from a subterranean, oil-containing formation penetrated by at least one injection well and at least one spaced-apart production well, said wells being in fluid communication with a substantial portion of the formation, comprising:

• (a) injecting carbon dioxide into the formation and producing fluids including oil from the formation via the production well for a predetermined period of time, thereby forming a carbon dioxide-swept zone in the formation;
• (b) thereafter injecting a mixture of carbon dioxide and an aqueous surfactant-starch solution into the formation via the injection well, said aqueous surfactant-starch solution capable of forming a stable foam with residual oil in the carbon dioxide-swept zone at formation conditions of temperature and pressure thereby significantly decreasing the permeability of that zone and diverting the carbon dioxide, noncondensible gas, into other portions of the formation;
• and
• (c) continuing to inject said mixture of carbon dioxide and aqueous surfactant-starch solution and recovering fluids including oil from the formation via the production well.