Heating of a subterranean formation

Claim 1

A METHOD OF RECOVERNG HYDROCARBONS FROM A SUBTERRANEAN FORMATION CONTAINING HYDROCARBONACEOUS MATERIAL THEREIN, AND HAVING SMALL PASSAGEWAYS RUNNING THERETHROUGH AND COMMUNICATING WITH AT LEAST ONE INJECTION WELL AND AT LEAST ONE PRODUCTION WELL PENETRATING SAID FORMATION, WHICH COMPRISES THE STEPS OF: (A) INJECTING THROUGH SAID INJECTION WELL A COMBUSTIBLE MIXTURE OF A GASEOUS FUEL AND AN OXYGEN-CONTAINING GAS WHILE PRODUCING SAID PRODUCTION WELL ONLY WHEN THE PRESSURE THEREAT REACHES A MINIMUM PRESSURE NECESSARY TO SUSTAIN FLASH BURNING IN THE FORMATION (B) WHEN SAID COMBUSTIBLE MIXTURE IS PRODUCED AT SAID PRODUCTION WELL, IGNITING SAID COMBUSTIBLE MIXTURE TO EFFECT FLASH BURNING IN SAID FORMATION WHEREBY THE FORMATION ADJACENT THE PASSAGEWAYS IS HEATED 5* TO 25* F., AND (C) REPEATING STEPS (A) AND (B) UNTIL THE IN-SITU HYDROCARBONACEOUS MATERIAL BECOMES FLOWABLE AND HYDROCARBONS ARE PRODUCED FROM THE FORMATION BY THE PRESSURE GRADIENTS ESTABLISHED WHEN THE PRODUCTION WELL IS PRODUCED, AND AS OFTEN THEREAFTER AS IS NECESSSARY TO SUSTAIN PRODUCTION.