Mobil Oil Corporation

Jerry M Waite

Ralph F Burdyn

Joseph G Savins

The recovery of oil by surfactant waterflooding involving the injection of a hydrocarbon slug followed by a thickened aqueous surfactant slug. The hydrocarbon slug is injected into the reservoir in an amount of at least 0.02 pore volume and has a viscosity less than that of the reservoir oil. The thickened surfactant slug comprises an aqueous solution of a surfactant system which includes an organic sulfonate surfactant and which functions to increase the viscosity of the aqueous liquid to a value at least as great as the viscosity of the reservoir oil while decreasing the oil-water interfacial tension. The surfactant slug may include one or more organic sulfonates, either alone or in mixture with a water-soluble aliphatic alcohol.

Oil recovery process employing a hydrocarbon slug and a thickened

Surfactant waterflooding process involving the injection of a hydrocarbon slug followed by a surfactant slug and a mobility control slug. The hydrocarbon slug has a viscosity less than that of the reservoir oil and is injected within the range of 0.01-0.04 pore volume. The surfactant slug is injected in an amount within the range of 0.05-0.3 pore volume and exhibits a surfactant concentration within the range of 0.5-4.0 weight percent. At least a portion of the mobility control slug has a viscosity at least as great as the viscosity of the hydrocarbon slug.

Surfactant waterflooding with hydrocarbon slug

Waterflooding process for the recovery of oil in which at least a portion of the injected water is thickened by the addition of a sulfonate surfactant and a C.sub.4 -C.sub.6 aliphatic alcohol having a hydrocarbon chain link of at least 3 carbon atoms. The action of the surfactant-alcohol system in increasing the viscosity of the water varies with the monovalent salt salinity of the water and the ratio of the amount of the sulfonate surfactant to the sum of the amounts of the sulfonate surfactant and alcohol in the water. A relatively viscous aqueous mobility control slug containing a sulfonate-alcohol system as previously described may be preceded by an aqueous surfactant slug. The aqueous solution of sulfonate surfactant and alcohol may be formulated and then aged for a time to allow the development of viscosity prior to injection into the oil reservoir. This viscosity development may be accelerated by heating.

Oil recovery by viscous waterflooding

Oil recovery by low tension waterflooding in which the common-ion effect is employed to suppress divalent metal ions in the low tension slug. A low tension slug comprising an aqueous medium containing an agent effective to reduce the oil-water interfacial tension is injected into a subterranean oil reservoir in order to displace oil therein to a production system. The low tension slug contains a salt having an anion in common with an alkaline earth metal salt which forms part of the reservoir rock material and which acts as a potential contributor of divalent ions to the slug. Thus where the reservoir rock contains calcium sulfate, sodium sulfate may be used in the low tension slug to suppress solubilization of the calcium sulfate into the low tension slug by the common-ion effect. The low tension slug may be preceded by a pretreatment slug also containing a salt having a common anion with an alkaline earth metal salt in the reservoir rock material.

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Dallas, TX, United States of America

Jerry M Waite