Protection of production well equipment in in situ combustion operation

Claim 1

APPARATUS COMPRISING IN COMBINATION: (1) A WELL EXTENDING INTO A PERMEABLE CARBONACEOUS STRATUM PROVIDED WITH A CASING EXTENDING FROM A WELLHEAD AT GROUND LEVEL TO SAID STRATUM; (2) A TUBING STRING WITHIN THE CASING OF (1) EXTENDING THRU SAID WELLHEAD TO SAID STRATUM; (3) A JACKETED TUBING SHOE ON THE LOWER END OF THE TUBING STRING OF (2) HAVING INLET MEANS IN AN UPPER SECTION AND AN OUTER MEANS IN A LOWER SECTION FOR FLUID COOLANT; (4) A COOLANT TUBING STRING WITHIN SAID CASING EXTENDING THRU SAID WELLHEAD TO THE PROXIMITY OF THE TUBING SHOE OF (3); (5) CONDUIT MEANS CONNECTING THE LOWER END OF THE TUBING STRING OF (4) WITH THE INLET MEANS OF (3); (6) A MACARONI TUBING STRING WITHIN THE TUBING STRING OF (4) PROVIDING AN ANNULUS THEREWITH AND CARRYING INTERNALLY A THERMOCOUPLE CABLE EXTENDING FROM OUTSIDE SAID WELLHEAD THRU THE LOWER END OF THE TUBING STRING OF (4); AND (7) TEMPERATURE SENSING MEANS ON THE LOWER END OF THE CABLE OF (6) OUTSIDE OF THE TUBING STRINGS OF (2), (4), AND (6) AND WITHIN THE CASING OF (1).