METHOD FOR RECOVERING OIL FROM A SUBTERRANEAN OIL CONTAININGFORMATION

摘要

The invention is a foam method for improving conformance during a steam flo od or carbon dioxide flood in a subterranean, oil-containing formation penetrat ed by at least one injection well and at least one production well. In a steam flood oil recovery process, sweep efficiency is improved by injecting steam until steam breakthrough occurs at the production well after which a mixture of steam, a noncondensib le gas, and an aqueous surfactant-starch solution is injected into the formation. The aqueous surfactant-starch solution forms a stable foam with the formation oil at formation conditions that reduce the permeability of the highly permeable steam swept zones thereby diverting the steam to other portions of the formation containing unswept oil. The starch is used as a partial substitute for the surfactant to improve the cost of the foam-forming mixture without reducing its effectiveness in increasing sweep efficiency.