High-pressure steam drive oil production process

Claim 1

A PROCES FOR PRODUCING OIL FROM AN OIL-BEARING STRATUM WHICH HAS BEEN PRODUCED BY NATURAL FLUID DRIVE COMPRISING THE STEPS OF: (A) WATER FLOODING A WELL PATTERN PENETRATING SAID STRATUM BY INJECTING WATER UNDER PRESSURE INTO AT LEAST ONE INJECTION WELL IN SAID PATTERN TO BUILD UP SUBSTANTIAL PRESSURE WITHIN THE WELL PATTERN AND IN THE SURROUNDING STRATUM AND PRODUCING FLUIDS INCLUDING OIL THRU AT LEAST ONE PRODUCTION WELL THEREIN; (B) FOLLOWING STEP (A), WITHOUT SUBSTANTIAL REDUCTION OF PRESSURE, STEM FLOODING SAID PATTERN BY INJECTING STEAM AT A PRESSURE SUBSTANTIALLY ABOVE STRATUM PRESSURE AT THE END OF STEP (A) THRU AT LEAST ONE INJECTION WELL IN SAID PATTERN AND PRODUCING FLUIDS INCLUDING OIL FROM AT LEAST ONE PRODUCTION WELL IN SAID PATTERN, THE VOLUME OF THE INJECTED STEAM BEING IN THE RANGE OF ABOUT 0.2 TO 0.65 OF THE PORE VOLUME OF SAID PATTERN; (C) FOLLOWING STEP (B), TERMINATING STEAM INJECTION AND DRIVING INJECTED STEAN THRU SAID PATTERN WITH COOL FLUID TO DRIVE A RESULTING HOT ZONE TOWARD THE PRODUCTION WELL(S) OF STEP (B); AND (D) RECOVERING FLUIDS INCLUDING OIL FROM THE PRODUCTION WELL(S) OF STEP (B) PRODUCED BY STEP (C).