Oil recovery by underground combustion

Claim 1

IN THE RECOVERY OF OIL FROM AN UNDERGROUND RESERVOIR STRATUM OF KNOW DEPTH AND THICKNESS AND HAVING A POROSITY OF FROM ABOIUT 12 TO ABOUT 25 PERCENT, BY A PROCESS INVOLVING COMBUSTION OF A PORTION OF THE OIL IN PLACE, THE STEPS OF MAKING AT THE EARTH''S SURFACE OVERLYING SAID STRATUM AN INTITIAL SET OF MEASUREMENTS OF A SEISMIC-WAVE-TRANSMITTING PROPERTY OF SAID STRATUM SUSCEPTIBLE TO BEING ALTERED BY THE HEAT OF THE COMBUSTION PROCESS, BY GENERATING SEISMIC WAVES NEAR THE GROUND SURFACE AND RECEIVING SAID WAVES AFTER REFLECTION AT A SUBSURFACE INTERFCE AT LEAST AS DEEP AS SAID STRATUM; INTITATING A COMBUSTION FRONT WITH SAID STRATUM AND MAINTAINING SAID COMBUSTION FRONT THEREIN BY SUPPLYING THROUGH AN OXYGEN INPUT WELL PENETRATING SAID STRATUM AT LEAST ABOUT 1.7 STANDARD CUBIC FEET OF OXYGEN PER HOUR TO EACH SQUARE FOOT OF AREA OF SAID FRONT, WHEREBY SAID FRONT IS CAUSED TO PROPAGATE THROUGH SAID STRATUM; REMEASURING AT INTERVALS SAID SEISMIC-WAVES-TRANSMITTING PROPERTY BY REPEATING AT LEAST PART OF SAID SET OF MEASUREMENTS, AND DETERMINING AND PLOTTING THE DIFFERENCES BETWEEN THE INITIAL AND THE REMEASURED VALUES OF SAID PROPERTY SO AS TO SHOW IN SEVERAL DIRECTIONS AROUND SAID INPUT WELL THE POSITIONS OF SAID FRONT FORMING THE BOUNDARY OF THE BURNED-OUT ZONE WHEREIN SAID PORPERTY HAS BEEN ALTERED; NOTING SAID FRONT POSITIONS AND VARYING THE OXYGEN-INJECTION RATE THROUGH SAID INPUT WELL IN ACCORDANCE WITH SAID REMEASURING STEP TO MAINTAIN THE SUPPLY RATE TO ALL PORTIONS OF SAID FRONT AT AT LEAST ABOUT 1.7 STANDARD CUBIC FEET OF OXYGEN PER HOUR PER SQUARE FOOT OF AREA OF SAID FRONT AS SHOWN BY THE FRONT POSITIONS LOCATED BY SAID REMEASURING STEP; AND RECOVERIMNG OIL FROM A PRODUCING WEL LATERALLY SPACED FROM SAID INPUT WELL.