METHOD FOR INITIATING AN OXYGEN DRIVEN IN-SITU COMBUSTION PROCESS

F-2575 METHOD FOR INITIATING AN OXYGEN DRIVEN IN-SITU COMBUSTION PROCESS A method for initiating an in-situ combustion process for the recovery of oil from a subterranean, viscous oil-containing formation wherein a combustible gas such as natural gas or methane and a mixture of oxygen and carbon dioxide containing 55 to 80 volume percent carbon dioxide is injected into a downhole burner in the injection well and ignited to produce combustion gases containing heat energy that pass into the formation. After the area of the formation surrounding the injection well reaches a temperature within the range of 500.degree.F to 800.degree.F, injection of the combustible gas is terminated and injection of the mixture of oxygen and carbon dioxide is continued to initiate in-situ combustion in the formation. Thereafter, essentially pure oxygen is injected into the formation to support in-situ combustion in the formation for the recovery of oil therefrom. Alternatively, after the combustion front has been formed, injection of the mixture of oxygen and carbon dioxide containing 55 to 80 volume percent carbon dioxide is continued until the combustion front has moved at least 30 feet into the formation before essentially pure oxygen is injected.