Well assembly for heating a subterranean formation

Claim 1

A WELL ASSEMBLY FOR EFFECTING HEATING OVER PORTIONS OF A SUBTERRANEAN FORMATION PENETRATED BY A WELL COMPRISING: (A) A CASING WITHIN SAID WELL EXTENDING SUBSTANTIALLY THE ENTIRE LENGTH OF SAID WELL FROM A POINT IN THE VICINITY OF THE SURFACE OF THE EARTH TO WITHIN THE VICINITY OF SAID FORMATION AND COMMUNICATING WITH SAID FORMATION, (B) CEMENTING MEANS BONDING SAID CASING TO THE WALL OF SAID WELL, ALLOWING COMMUNICATION BETWEEN THE INTERIOR OF SAID CASING AND SAID FORMATION BUT PREVENTING COMMUNICATION BETWEEN SAID INTERIOR OF SAID CASING AND OTHER FORMATIONS, (C) A CASINGHEAD ATTACHED TO SAID CASING AT THE UPPER END THEREOF, (D) AN APERTURE HAVING SEALING MEANS IN SAID CASING HEAD, (E) A PRIMARY AIR CONDUIT SLIDABLY POSITIONED WITHIN SAID SEALING MEANS AND SAID APERTURE IN SAID CASINGHEAD, (F) A FUEL STRING CONCENTRICALLY LOCATED WITHIN SAID PRIMARY AIR CONDUIT AND EXTENDING SUBTANTIALLY THE ENTIRE LENGTH THEREOF, (G) MEANS PREVENTING LEAKAGE OF AIR FROM THE UPPER END OF SAID PRIMARY AIR CONDUIT, (H) MEANS PREVENTING LEAKAGE OF FUEL GAS FROM THE UPPER END OF SAID FULE STRING, (I) MEANS FOR SUPPLYING PRIMARY AIR TO SAID PRIMARY AIR CONDUIT, (J) MEANS FOR SUPPLYING FUEL GAS TO SAID FUEL STRING, (K) MEANS FOR SUPPLYING SECONDARY AIR TO SAID CASING, (L) A HEAT SHIELD POSITIONED ON SAID PRIMARY AIR CONDUIT AT THE BOTTOM THEREOF ADJACENT SAID FORMATION,