Control method in underground combustion drives

Claim 1

A PROCESS FOR THE SECONDARY RECOVERY OF HYDROCARBONS, COMPRISING THE STEPS OF: (A) COMPLETING A GAS INJECTION WELL INTO A RELATIVELY PERMEABLE HYDROCARBON-BEARING FORMATION; (B) COMPLETING A PRODUCTION WELL INTO THE HYDROCARBON-BEARING FORMATION AT A SPACED LOCATION WITH RESPECT TO THE INJECTIONW ELL; (C) PROVIDING THE PRODUCTION WELL WITH MEANS FOR SEPARATING ANY SEPARATELY PRODUCING GASES AND LIQUIDS; (D) INITIATING UNDERGROUND COMBUSTION IN THE HYDROCARBON-BEARING FORMATION IMMEDIATELY SURROUNDING THE INJECTION WELL AND ADVANCING THE COMBUSTION FRONT THEREFROM BY INJECTING COMBUSTION-SUPPORTION GAS INTO THE INJECTION WELL AT A RATE AT WHICH THE UPPER EDGE OF THE COMBUSTION FRONT RECHES THE PRODUCTION WELL BEFORE THE LOWER EDGE; (E) PRODUCING FLUIDS FROM SAID PRODUCTION WELL AND ANALYZING THE GAS SO PRODUCED TO DETECT THE PRESENCE OF UNREACTED COMBUSTION-SUPPORTING GAS THEREIN; AND (F) RESTRICTING PRODUCTION OF GAS FROM SAID PRODUCTION WELL WHEN UNREACTED COMBUSTION-SUPPORTING GAS IS DETECTED THEREIN SUFFICIENTLY TO PREVENT THE TEMPERATURE FROM EXCEEDING 700*F. IN SAID PRODUCTION WELL WHILE CONTINUING TO PRODUCE LIQUID EFFLUENT THEREFROM.