Patent ID: 6263965
Filing Date: 2001-07-24
Classification: E21B

Abstract:
A thermal method for recovering normally immobile hydrocarbon oil from a subsurface formation containing a tar sand deposit comprising:(a) establishing at least one substantially vertical production bore hole extending from the surface of the earth to at least the bottom of said subsurface formation;(b) providing a plurality of auxiliary bore holes extending downwardly from the surface of the earth through the tar sand formation to substantially the bottom thereof and then substantially horizontally near the bottom of the tar sand formation and converging radially inward to the at least one production bore hole, each said radial auxiliary bore hole containing a perforated or slotted tube with the entire portion of the tube passing through the tar sand formation being perforated or slotted;(c) continuously injecting steam downwardly through said perforated or slotted tubes whereby the steam discharges through the perforations or slots and into the tar sand formation to reduce the viscosity of the normally immobile oil, the injected steam having a temperature and pressure which both decrease as the steam travels downwardly through the tubes whereby a substantial proportion of the steam being injected into the formation via the portion of each tube extending downwardly through the tar sand formation reduces the viscosity of the normally immobile oil over an area extending substantially between the perforated tube and the top of the tar sand formation with this viscosity reducing area expanding radially and moving axially inwardly toward the at least one vertical production bore hole thereby creating an expanding generally conical-shaped production chamber in response to the decreasing steam temperature and pressure; and(d) simultaneously continuously draining the less viscous oil and steam condensate thus obtained downwardly by gravity to the bottom of the production chamber 7 then into the horizontal tubes by way of said perforations or slots and thence into the bottom of the at least one vertical production bore hole for collection.