Recovery of hydrocarbons from a subterranean reservoir by heating

Claim 1

A PROCEDURE FOR RECOVERING HYDROCARBONS FROM A SUBTERRANEAN FORMATION CONTAINING HYDROCARBON MATERIAL COMPRISING: (A) PASSING AN OXIDIZING GAS THROUGH AID FORMAION FROM AN INPUT WELL TO AN OUTPUT WELL TO EFFECT AUTOOXIDATION OF SAID HYDROCARBON MATERIAL IN SAID FORMATION AND THEREBY HEAT SAID HYDROCARBON MATERIAL TO AN ELEVATED TEMPERATURE LESS THAN THE IGNITION TEMPERATURE OF THE HYDROCARBON MATERIAL IN SAID FORMATION AND THEREUPON, (B) REDUCING THE OXYGEN CONTENT OF SAID OXIDIZING GAS PASSING THROUGH THE FORMATION SUFFICIENTLY TO PREVENT IGNITION AND COMBUSTION OF SAID HYDROCARBON MATERIAL WHENEVER THE TEMPERATURE OF SAID HYDROCARBON MATERIAL IN SAID FORMATION BEGINS TO APPROACH THE IGNITION TEMPERATURE OF SAID HYDROCARBON MATERIAL, (C) MAINTAINING THE PASSAGE OF OXIDIZING GAS THROUGH SAID FORMATION UNTIL THE FORMATION IS HEATED BY AUTOOXIDATION TO AN AVERAGE TEMPERATURE SUCH THAT THE MOBILITY RATIO, WHICH IS THE RATIO OF THE MOBILITY OF THE DRIVING FLUID TO THE MOBILITY OF THE DRIVEN FLUID THEREIN IS BELOW 10 AND (D) THEREAFTER PASSING AN INERT DRIVING FLUID THROUGH SAID FORMATION FROM AN INPUT WELL TO AN OUTPUT WEL TO DRIVE HEATED FLUID HYDROCARBONS WITHIN SAID FORMATION TO SAID LATTER OUTPUT WELL.