Recovery of hydrocarbons from underground formations by in situ combustion

Claim 1

A PROCESS FOR RECOVERING HYDROCARBONS BY IN SITU COMBUSTION FROM A GAS PERVIOUS UNDERGROUND HYDROCARBON BEARING FORMATION BY EXPLOITATION THROUGH A WELL PATTERN OF A CENTRAL WELL AND A PLURALITY OF WELLS SURROUNDING SAID CENTRAL WELL IN RING-LIKE FASHION COMPRISING (A) PUMPING AIR DOWN INTO A FIRST PAIR OF DIAMETRICALLY LOCATED WELLS OF SAID PATTERN, WHILE (B) CONCURRENTLY PRODUCING HYDROCARBONS FROM A SECOND PAIR OF DIAMETRICALLY LOCATED WELLS, THE DIAMETERS OF THE PAIRS OF WELLS CROSSING EACH OTHER, (C) SHUTTING IN SAID FIRST PAIR OF WELLS UPON BREAKTHROUGH OF AIR AT SAID SECOND PAIR OF WELLS, (D) INJECTING AIR INTO SAID CENTRAL WELL AND IGNITING THE HYDROCARGON BEARING FORMATION THEREAT, THEREBY DEVELOPING A CONCURRENT IN SITU COMBUSTION FRONT WITH RESPECT TO SAID SECOND PAIR OF WELLS, AND (E) UPON BREAKTHROUGH OF SAID IN SITU COMBUSTION FRONT AT SAID SECOND PAIR OF WELLS, AGAIN INJECTING AIR INTO SAID FIRST PAIR OF WELLS WHILE CONTINUING PRODUCING HYDROCARBONS AT SAID SECOND PAIR OF WELLS.