Underground combustion process

Claim 1

IN A PROCESS FOR CONDUCTING COMBUSTION IN A HYDROCARBON RESERVOIR PENETRATED BY AN INJECTION WELL AND A PRODUCTION WELL BY FIRST IGNITING THE FACE OF SAID RESERVOIR ADJACENT SAID INJECTION WELL TO ESTABLISH A COMBUSTION FRONT FOLLOWED BY INTRODUCING AN OXYGEN-CONTAINING GAS INTO SAID RESERVOIR VIA SAID INJECTION WELL TO DRIVE SAID FRONT TOWARD SAID PRODUCTION WELL, SAID RESERVOIR CONTAINING HIGHLY PERMEABLE STRATA PRIOR TO INITIATION OF SAID FORWARD COMBUSTION OPERATION, AND WHEREIN THE OXYGEN CONCENTRATION IN THE EFFLUENT GAS FROM SAID PRODUCTION WELL CONTAINS AT LEAST ABOUT 5 PERCENT OF FREE OXYGEN, THE METHOD OF STIMULATING AND SUSTAINING FLOW OF HYDROCARBONS INTO SAID PRODUCTION WELL WHICH COMPRISES IGNITING THAT PORTION OF SAID RESERVOIR ADJACENT SAID PRODUCTION WELL AND ESTABLISHING A REVERSE COMBUSTION FRONT BY CONTACTING SAID LAST-MENTIONED IGNITED PORTION WITH FREE OXYGEN ENTERING SAID PRODUCTION WELL FROM SAID RESERVOIR, WHEREBY FORWARD AND REVERSE COMBUSTION ARE CARRIED OUT SIMULTANEOUSLY IN SAID RESERVOIR, AND RECOVERING HYDROCARBON FLUIDS FROM SAID PRODUCING WELL.