An integrated in situ combustion process for producing subterranean carbonaceous deposits in which the resulting flue gas of low heating value is combusted over an oxidation catalyst at substoichiometric conditions and is expanded in a gas turbine which drives the air compressor for injecting the combustion air into the underground carbonaceous deposit. An oxidation catalyst is provided for reducing carbon monoxide in the combusted flue gas comprising platinum and at least one metal cocatalyst selected from Groups IA, II, III, VIIB and VIII up through atomic No. 45, the lanthanides, chromium, silver, tin and antimony.