Tar-sand oil cannot be pushed to the production well by the injection of water as in water flooding. It can, however, be produced by mining and aboveground extraction. Four elements must be present for the in situ production of oil from tar-sand deposits: (1) Establishment of communication between walls; (2) reduction of oil viscosity within the formation; (3) maintenance of the flow path once established; and (4) the addition of energy through fluid injection.