In situ combustion for oil recovery in tar sands, oil shales and conventional petroleum reservoirs

Claim 1

IN A METHOD FOR THE RECOVERY OF HYDROCARBONS FROM UNDERGROUND FORMATIONS PENETRATED AT SPACED POINTS BY AN INJECTION WELL AND A PRODUCING WELL WELL WHEREIN COMBUSTION IS INITIATED IN SUCH A FORMATION PREPARED FOR IN SITU COMBUSTION AND A COMBUSTION FRONT IS PROPAGATED THROUGH A PREPARED PORTION OF SAID FORMATION HAVING AN OXIDATION CATALYST DISTRIBUTED THEREIN, THE IMPROVEMENT WHICH COMPRISES PROPAGATING A COMBUSTION FRONT THROUGH THE FORMATION BY VARYING, IN RELATION TO OXIDATION CATALYST CONCENTRATION IN THE PREPARED PORTION, THE VELOCITY AND OXYGEN CONTENT OF A CONTINUOUS FLOW OF A GAS MIXTURE INTRODUCED THROUGH THE INJECTION WELL FOR DIRECTING SAID FRONTAL MOVEMENT, SO AS TO ESTABLISH A MAXIMUM TEMPERATURE IN SAID FRONTAL MOVEMENT CAPABLE OF MAINTAINING DISTILLATION TEMPPERATURES BUT INSUFFICIENT TO CAUSE COKING OF AN APPRECIABLE AMOUNT OF THE HYDROCARBONS WITHIN THE PREPARED PORTION DURING RECOVERY OF A MAJOR PORTION OF THE HYDROCARBON CONTENT OF SAID PREPARED PORTION, AND RECOVERING EVOLVED PRODUCTS THROUGH THE PRODUCING WELL.