tar sand deposit in an area proximate to a tar sand deposit which is not minable and which requires the use of in situ production technique to recover hydrocarbons thereform the mined tar sands are processed on site by various conventional processes such as a 34 hot water process 34 to produce a bitumen product that is upgraded by delayed or fluid coking and further upgrading the liquid product produced from the coking step by hydrogen treatment to produce an upgraded oil product and a hydrogen sulfide by product processes of this character are described in hydrocarbon processing vol 61 september 1982 pages 108 139 140 154 and 100 163 the disclosure of which is hereby incorporated by reference the hydrogen sulfide is recovered and used in conjunction with an in situ combustion operation to recover hydrocarbons from the adjacent tar sand formation that are not amenable to recovery by surface mining for the purpose of this invention an unminable formation is a formation with an overburden greater than 500 feet in the recovery of hydrocarbons bitumen by the in situ combustion phase of the present invention the subterranean tar sand formation is penetrated by at least one injection well and at last one spaced apart production well both wells being in fluid communication with a substantial portion of the oil containing formation the hydrogen sulfide recovered from upgrading.