Texaco Inc.

James E Varnon

Lawrence E Whittington

Mohan V Kudchadker

Alfred Brown

Vernon H Schievelbein

Disclosed is a method for conducting an enhanced oil recovery process comprising injecting an oil displacing fluid into an injection well and recovering petroleum displaced by the fluid from one or more spaced-apart production wells, by an improved method in which the sweep efficiency or horizontal conformance of the displacement process is increased. A fluid is injected into the producing well, which fluid has a viscosity not substantially greater than the viscosity of water at the conditions of injection, but which reacts with oil present in the formation, forming a viscous emulsion which restricts the flow of fluids through the portion of the formation contacted by the emulsion-forming fluid. As a result of this treatment, there is a reduction in tendency for the displaced and injected fluids to form cusps as they approach the production well, thereby failing to sweep substantial portions of the formation. The injected fluid contains one or more surfactants specifically tailored to form a viscous emulsion with the particular formation crude oil and formation water or brine exhibiting maximum viscosity at formation conditions. The viscous emulsion-forming fluid may be injected into all of a group of wells surrounding a central injection well in approximately equal amounts, for the purpose of improving sweep efficiency, or the treatment may be selectively applied to certain of the wells where the formation exhibits a preferred direction of permeability, or where for other reasons the pattern integrity is poor.

High sweep efficiency enhanced oil recovery process

The conformance of an enhanced oil recovery process, including water flood, surfactant or other chemicalized water flood process, in a formation containing at least two zones of varying permeability, the permeability of one zone being at least 50 percent greater than the permeability of the other zone, is improved by flooding until the higher permeability zone has been depleted, after which a fluid is injected into the high permeability zone, said fluid having relatively low viscosity at the time of injection and containing a mixture of surfactants or surface active agents which promote the formation of a coarse emulsion in the flow channels of the formation which reduces the permeability of the high permeability zone. Since the viscosity of the fluid injected into the previously flooded, high permeability zone is no greater than water, it is injected easily into the zone and moves through substantially the same flow channels as water would move in the formation. After the permeability of the first zone has been reduced substantially, water flooding may then be accomplished in the second zone which was originally not invaded by the injected water since its permeability was substantially less than the permeability of the first zone.

High conformance enhanced oil recovery process

The conformance of a water flood oil recovery process, including surfactant or other chemicalized water flood process, in a formation containing at least two zones of varying permeability, the permeability of one zone being at least 50 percent greater than the permeability of the other zone, is improved by flooding until the higher permeability zone has been depleted, after which a fluid is injected into the high permeability zone, said fluid having relatively low viscosity at the time of injection and containing surface active agents which promote the formation of a coarse emulsion in the flow channels of the formation which reduces the permeability of the high permeability zone. Since the viscosity of the fluid injected into the previously water flooded, high permeability zone is no greater than water, it is injected easily into the zone and moves through substantially the same flow channels as water would move in the formation. After the permeability of the first zone has been reduced substantially, water flooding may then be accomplished in the second zone which was originally not invaded by the injected fluid since its permeability was substantially less than the permeability of the first zone. The surface active agent is tailored to exhibit optimum emulsion formation properties with the particular aqueous fluid present in the flow channels of the formation to be treated. The optimum emulsifying surfactant comprises a mixture of an alkylpolyalkoxyalkylene sulfonate or an alkylarylpolyalkoxylalkylene sulfonate and an organic sulfonate such as petroleum sulfonate.

The conformance of an enhanced oil recovery process, including waterflood, surfactant or other chemicalized water flood process, in a formation containing at least two strata or zones of varying permeability, the permeability of one zone being at least 50 percent greater than the permeability of the other zone, is improved by flooding until the higher permeability zone has been depleted, after which an aqueous fluid is injected into the high permeability zone, said fluid having relatively low viscosity at the time of injection and containing a blend of surface active agents which promote the formation of a coarse viscous emulsion in the flow channels of the formation which reduces the permeability of the high permeability zone. After the permeability of the first zone has been reduced substantially, flooding may then be accomplished in the second zone which was originally not invaded by the injected oil recovery fluid. The surface active agents are individually tailored and the ratio of dissimilar surfactants balanced to exhibit optimum viscous emulsion formation properties. The optimum emulsifying surfactant comprises a mixture of an organic sulfonate such as petroleum sulfonate and a solubilizing co-surfactant such as an alkyl or alkylarylpolyalkoxy alkylene sulfonate and/or a low molecular weight alcohol.

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Houston, TX, United States of America

James E Varnon