Abstract: A subterranean, viscous oil-containing formation, e.g. tar sands, which has previously been exploited by an in-situ combustion operation to recover the maximum amount of oil therefrom and leaving a solid coke like residue in the formation, is first saturated with a combustible gas such as methane, ethane, propane, natural gas or mixtures thereof, thereafter reinitiating in-situ combustion and then injecting a mixture of an oxygen-containing gas and steam to convert the coke like residue to a combustible product gas consisting predominantly of carbon monoxide and hydrogen within the formation. The combustible product gas is recovered and may be utilized directly as a fuel gas, or may be utilized as feed stock for petro chemical manufacturing processes.

Abstract: Hydrocracked oils are stabilized against deterioration due to exposure to light and/or air by adding to them a small amount of aromatic amine having a nitro group, the amino and nitro groups being ortho or para to each other.