Patent ID: 7422063
Filing Date: 2008-09-09
Classification: E21B

Abstract:
1. A method for recovering hydrocarbons from a subterranean formation containing viscous oil, oil shale, tar sands or other heavy hydrocarbons; the method comprising the steps of: (a) drilling a central wellbore down to the hydrocarbon bearing formation, thereby penetrating the formation and the under-burden zones; (b) reaming out the said central wellbore selectively to form a large production cavity located below the hydrocarbon bearing formation; (c) providing a plurality of perforations in the central vertical wellbore at pre-selected intervals in the upper and lower portion of the said formation; (d) installing a downhole wellbore packer between upper and lower perforations; (e) installing production tubing through the said packer; (f) installing a downhole production pump through the said packer to lift the produced oil to the surface through the said production tubing to lift the produced fluids and displaced fluids to the surface; (h) injecting a fluid in the central wellbore and heating the central wellbore and surrounding formation for sufficient time and at a calculated temperature so that the resultant steam flows through upper injection perforations to form an annular hot zone of increased fluid conductivity, so as to create a vertical flow of heated low viscosity oil and hot water produced from condensed steam, towards lower production perforations; (i) collecting hot oil and water in the said production cavity; (j) lifting the produced oil to the surface by using the said downhole production pump.