Importance

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Abstract

A method of extracting bitumen from a subsurface tar sand bed wherein a shell of frozen earth is formed around the periphery of at least a portion of the tar sand bed, followed by recovering bitumen from such portion of the tar sand bed within the shell of frozen earth by suitable means such as, for example, solvent extraction. Also disclosed is apparatus for freezing the earth surrounding one of a plurality of boreholes drilled in the earth within earth freezing distance of each other around the periphery of such portion of the tar sand bed. The apparatus comprises concentric outer and inner conduits with the outer conduit having two strips of thermal insulation extending along substantially the full length of the exterior surface of the outer conduit, separated by two strips, preferably longitudinally finned, of relatively high thermal conductivity extending along substantially the full length of the exterior surface of the outer conduit so as to provide a predetermined freezing pattern about the axis of a borehole when refrigerant is circulated through the apparatus.

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First Claim