Completion for tar sand substrate

Method and apparatus for recovering hydrocarbons from a subterranean formation in which a well completion, including a well liner, lies in a generally horizontal disposition within the hydrocarbon productive substrate. The liner encloses conductor means for delivering a stream of a hot stimulating agent to the well's remote or injection end, and means for regulating the production of bitumen emulsion from the producing end thereof. A fluid impervious barrier is movably interposed in the well liner between the injection end and the producing end to establish a pressure differential across said barrier thereby directing a flow of stimulating agent into the substrate. Said agent, by liquefying bitumen, creates a pattern of paths along which the mixture flows toward the well's lower pressure producing end. By progressively moving the barrier toward said producing end, the flow path pattern can be extended into a broader area of the substrate.