Recovery of petroleum from viscous asphaltic petroleum containing formations including tar sand deposits

patentPetroleum materials may be effectively recovered from subterranean, viscous, asphaltic or bituminous formations such as tar sand deposits by first injecting into the tar sand formation a paraffinic hydrocarbon at a temperature below 300.degree. F which precipitates asphaltic material from the asphaltic petroleum in the formation. Next, solvent injection is terminated and air is injected into the formation, and the formation is ignited to accomplish in situ combustion within the tar sand reservoir utilizing the precipitated asphaltic materials for fuel for the in situ combustion reaction. Reaction temperatures higher than normal in situ combustion temperatures are produced, facilitating thermal cracking and in situ hydrogenation to up grade the produced crude within the tar sand reservoir