Process for secondary recovery of petroleum using stabilized microemulsions

Claim 1

THE PROCESS COMPRISING MIXING TO FORM A WATER-INOIL MICROEMULSION SHOWING SUBSTANTIALLY NO TYNDALL EFFECT AND SUBSTANTIALLY STABLE TO IONS IN A PARTICULAR OIL-BEARING FORMATION (A) AMOUNTS OF WATER, (B) HYDROCARBON, (C) AT LEAST ONE SUFACTANT WHICH IS RELATIVELY SOLUBLE IN OIL AND RELATIVELY INSOLUBLE IN WATER AND (D) AT LEAST ONE ADDITIONAL SURFACTANT WHICH IS RELATIVELY SOLUBLE IN WATER AND RELATIVELY INSOLUBLE IN OIL, THE SURFACTANTS BEING ADDED IN AMOUNTS SUFFICIENT TO FORM THE AFORE-CHARACTERIZED MICROEMULSION AND THE SAID WATER CONTENT BEING IN EXCESS OF THAT AMOUNT REQUIRED TO CAUSE A SUBSTANTIAL INCREASE IN VISCOSITY ON ADDITION OF THE WATER TO AN ANHYDROUS OILSURFACTANT MIXTURE AND A PEAKING OR LEVELING OF THE VISCOSITY RESULTING FROM ADDING WATER TO THE ANHYDROUS SYSTEM; INJECTING THE SAID MICROEMULSION INTO AN OIL-BEARING FORMATION, HAVING AT LEAST ONE EACH OF AN INJECTION MEANS AND OIL-PRODUCTION MEANS DRILLED THEREIN, THROUGH SAID AT LEAST ONE INJECTION MEANS; THEREAFTER INJECTING A DISPLACING FLUID INTO SAID FORMATION THROUGH SAID AT LEAST ONE INJECTION MEANS AND FINALLY RECOVERING OIL THROUGH SAID AT LEAST ONE PRODUCTION MEANS.