Surfactants for oil recovery by waterfloods

Claim 1

AN IMPROVEMENT IN WATERPROOFING OPERATION FOR RECOVERING OIL FROM SUBTERRANEAN RESERVOIRS INVOLVING THE INJECTION OF AQUEOUS LIQUID THROUGH AT LEAST ONE INJECTION BOREHOLE PENETRATING SAID RESERVOIR, FORCING SAID AQUEOUS LIQUID INTO SAID RESERVOIR THROUGH SAID INJECTION BOREHOLE, AND RECOVERING OIL DISPLACED FROM SAID RESERVOIR BY SAID AQUEOUS LIQUID AT A LOCATION SPACED FROM SAID INJECTION BOREHOLE, SAID IMPROVEMENT COMPRISING INCORPORATING IN AT LEAST THE INITIAL PORTION OF SAID AQUEOUS LIQUID A COMPOSITION CONTAINING BOTH LOW MOLECULAR WEIGHT ALKYL ARYL SULFONATES WHICH ARE WATER SOLUBLE AND HIGH MOLECULAR WEIGHT ALKYL ARYL SULFONATES WHICH ARE WATER INSOLUBLE, SAID LOW MOLECULAR WEIGHT ALKYL ARYL SULFONATES BEING PRESENT IN AT LEAST CRITICAL MICELLE CONCENTRATION WITH AMPHIPHILIC MOLECULES COMPRISING SAID HIGH MOLECULAR WEIGHT ALKYL ARYL SULFONATES PENETRATING INTO AND SWELLING THE MICELLES, WHEREBY THE INTERFACIAL TENSION BETWEEN SAID PORTION OF SAID AQUEOUS LIQUID CONTAINING SAID MIXTURE AND THE RESIDUAL OIL IN SAID RESERVOIR IS SUBSTANTIALLY REDUCED ENABLING SAID PORTION TO DISPLACE SAID OIL FROM SAID RESERVOIR WITH GREATER EFFICIENCY.