Residual oil recovery process using water containing a surfactant

Claim 1

A WATER FLOODING PROCESS FOR THE RECOVERY OF RESIDUAL OIL FROM AN UNDERGROUND OIL-BEARING FORMATION HAVING AN INJECTION WELL AND A PRODUCTION WELL SPACED FROM THE INJECTION WELL PENETRATING THE FORMATION COMPRISING FORMING A FIRST PASSAGE EXTENDING INTO THE OILBEARING FORMATION FROM THE INJECTION WELL, FORMING A SECOND PASSAGE EXTENDING INTO THE OIL-BEARING FORMATION FROM THE PRODUCTION WELL, SAID FIRST AND SECOND PASSAGES BEING SUBSTANTIALLY PARALLEL, INJECTING AN AQUEOUS DISPERSION OF A SURFACTANT FROM THE INJECTION WELL INTO THE FORMATION AT A PRESSURE WHEREBY THE PRESSURE DIFFERENTIAL IN POUNDS PER SQUARE INCH BETWEEN THE FIRST AND SECOND PASSAGES PER FOOT OF DISTANCE BETWEEN THE PASSAGES DIVIDED BY THE INTERFACIAL TENSION IN DYNES PER CENTIMETER BETWEEN THE OIL IN THE FORMATION AND THE AQUEOUS DISPERSION EXCEEDS ABOUT 5 DISPLACING SAID DISPERSION THROUGH THE FORMATION TO DRIVE OIL THROUGH THE FORMATION TO THE PRODUCTION WELL, THE AREA OF THE FORMATION EXPOSED TO EACH OF SAID FIRST AND SECOND PASSAGES BEING AT LEAST 1/10 OF THE AREA SWEPT BY THE AQUEOUS DISPERSION MEASURED PERPENDICULAR TO THE DIRECTION OF FLOW OF THE AQUEOUS DISPERSION, AND PRODUCING OIL THROUGH THE PRODUCTION WELL.