patentRecovery of viscous petroleum such as from a thick tar sand formation is assisted using a closed-loop flow path formed in a production well extending from the earth's surface through a substantial portion of the formation for conducting hot fluid to reduce the viscosity of the petroleum in the formation to develop a first potential passage in the formation outside the flow path into which a hot drive fluid is injected through a injection well to promote movement of the petroleum to the production well for production and to develop a second potential passage for fluid flow in the formation from a linearly spaced apart injection well for injection of a hot drive fluid to further promote movement of additional petroleum to the production...
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