Secondary recovery method

Claim 1

A SECONDARY RECOVERY PROCESS IN WHICH AT LEAST ONE INJECTION WELL AND AT LEAST ONE PRODUCTION WELL PENETRATES AN OIL BEARING FORMATION FROM WHICH OIL IS TO RECOVERED CONSISTING OF THE STEPS OF: (A) INTRODUCING THROUGH SAID INJECTION WELL AND INTO CONTACT WITH THE OIL IN SAID FORMATION A SLUG OF A LIGHT HYDROCARBON CRUDE OIL DISTILLATE HAVING A BOILING POINT BELOW THE BOILING POINT OF GAS-OIL IN AN AMOUNT EQUAL TO BETWEEN 10 AND 20% OF THE PORE VOLUME OF SAID FORMATION, SAID SLUG CONTAINING BETWEEN 2.5% AND 10%A BY WEIGHT OF A HIGH BOILING NAPHTHENIC ACID HAVING A MOLECULAR WEIGHT FROM 300 TO 420; (B) THEREAFTER INTRODUCING THROUGH SAID INJECTION WELL AN AQUEOUS SODIUM HYDROXIDE SOLUTION IN AN AMOUNT OF SEVERAL PORE VOLUMES OF SAID FORMATION WHEREBY SOME OF THE DISPERSED HIGH BOILING NAPHTHENIC ACID IS CONVERTED TO A SURFACE ACTIVE COMPOUND WHICH IS CAPABLE OF EMULSIFYING AND MAINTAINING IN AN EMULSION STATE A PORTION OF SAID FORMATION OIL AND THEREBY FACILITATING THE DISPLACEMENT OF SAID FORMATION OIL TOWARD SAID PRODUCTION WELL BY SAID AQUEOUS SOLUTION INTRODUCED THROUGH SAID INJECTION WELL; AND (C) RECOVERING FORMATION OIL FROM SAID PRODUCTION WELL.