Method and apparatus for treatment of subsurface formations

Apparatus for freezing the earth surrounding a borehole in a predetermined pattern about the axis of said borehole, comprising:

• first longitudinal tubular conduit means having a closed upper end and a closed lower end and having first connecting means at the closed upper end for connecting the interior of said first tubular conduit means in fluid flow communication with refrigerant input conduit means;
• second longitudinal tubular conduit means having a closed upper end and a open lower end and disposed within said first tubular conduit means with the open lower end of said second tubular conduit means positioned near the closed lower end of said first tubular conduit means and having second connecting means at the closed upper end of said second tubular conduit means for connecting the interior of said second tubular conduit means in fluid flow communication with refrigerant output conduit means;
• and
• the outer surface of said first tubular conduit means including two strips of relatively low thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means between the first and second ends thereof, and further including two strips of relatively high thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means, with said two longitudinally extending strips of relatively low thermal conductivity alternating with said two longitudinally extending strips of relatively high thermal conductivity about the longitudinal axis of said first longitudinal tubular conduit means and with each of said two longitudinally extending strips of relatively high thermal conductivity extending through an angle of about 60.degree. about the longitudinal axis of said first longitudinal tubular conduit means.

A method of recovering bitumen from a subsurface tar sand bed comprising:

• drilling a plurality of downwardly extending boreholes spaced within earth freezing distance of each other about the periphery of at least a portion of said tar sand bed;
• circulating refrigerant in said boreholes in such a manner as to freeze the earth surrounding said boreholes in a predetermined pattern about the axis of each of said boreholes, said pattern extending substantially farther radially outwardly along a first line through the axis of each borehole toward the next adjacent borehole through the axis of each borehole and substantially normal to said first line, thereby forming a shell of frozen earth around said periphery of at least a portion of said tar sand bed;
• and
• recovering bitumen from at least a portion of said tar sand bed within said shell of frozen earth.

A method of recovering bitumen from a subsurface tar sand bed comprising:

• forming a plurality of generally downwardly extending boreholes in the earth with said boreholes spaced within earth freezing distance one from the other about the periphery of at least a portion of said tar sand bed;
• circulating refrigerant through apparatus in each of said boreholes to freeze the earth surrounding each of said boreholes and intermediate adjacent pairs of said boreholes to thereby form a shell of frozen earth around said periphery of at least a portion of said tar sand bed, said apparatus comprising:
• first longitudinal tubular conduit means having a closed upper end and a closed lower end and having first connecting means at the closed upper end for connecting the interior of said first tubular conduit means in fluid flow communication with refrigerant input conduit means;
• second longitudinal tubular conduit means having a closed upper end and an open lower end and disposed within said first tubular conduit means with the open lower end of said second tubular conduit means positioned near the closed the lower end of said first tubular conduit means and having second connecting means at the closed upper end of said second tubular conduit means for connecting the interior of said second tubular conduit means in fluid flow communication with refrigerant output conduit means;
• and
• the outer surface of said first tubular conduit means having at least one strip of relatively low thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means between the first and second ends thereof, and further having at least one strip of relatively high thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means;
• and
• recovering bitumen from said at least a portion of said tar sand bed within said shell of frozen earth.

A system for recovering bitumen from a subsurface tar sand bed comprising:

• a plurality of boreholes spaced within earth freezing distance one from the other about the periphery of at least of portion of said tar sand bed;
• apparatus for freezing the earth surrounding a borehole in a predetermined pattern about the axis thereof positioned in each of said plurality of boreholes, said apparatus comprising;
• first longitudinal tubular conduit means having a closed upper end and a closed lower end and having first connecting means at the closed upper end for connecting the interior of said first tubular conduit means in fluid flow communication with refrigerant input conduit means;
• said second longitudinal tubular conduit means having a closed upper end and an open lower end and disposed within said first tubular conduit means with the open lower end of said second tubular conduit means positioned near the closed lower end of said first tubular conduit means and having second connecting means at the closed upper end of said second tubular conduit means for connecting the interior of said second tubular conduit means in fluid flow communication with refrigerant output conduit means;
• and
• the outer surface of said first tubular conduit means including two strips of relatively low thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means between the first and second ends thereof, and further including two strips of relatively high thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means, with said two longitudinally extending strips of relatively low thermal conductivity alternating with said two longitudinally extending strips of relatively high thermal conductivity about the longitudinal axis of said first longitudinal tubular conduit means and with each of said two longitudinally extending strips of relatively low thermal conductivity extending through an angle of about 120.degree. about the longitudinal axis of said first longitudinal tubular conduit means.

A system for recovering bitumen from a subsurface tar sand bed comprising:

• a plurality of boreholes spaced within earth freezing distance one from the other about the periphery of at least of portion of said tar sand bed;
• apparatus for freezing the earth surrounding a borehole in a predetermined pattern about the axis thereof positioned in each of said plurality of boreholes, said apparatus comprising;
• first longitudinal tubular conduit means having a closed upper end and a closed lower end and having first connecting means at the closed upper end for connecting the interior of said first tubular conduit means in fluid flow communication with refrigerant input conduit means;
• said second longitudinal tubular conduit means having a closed upper end and an open lower end and disposed within said first tubular conduit means with the open lower end of said second tubular conduit means positioned near the closed lower end of said first tubular conduit means and having second connecting means at the closed upper end of said second tubular conduit means for connecting the interior of said second tubular conduit means in fluid flow communication with refrigerant output conduit means;
• and
• the outer surface of said first tubular conduit means including two strips of relatively low thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means between the first and second ends thereof, and further including two strips of relatively high thermal conductivity extending longitudinally along at least a portion of the outer surface of said first tubular conduit means, with said two longitudinally extending strips of relatively low thermal conductivity alternating with said two longitudinally extending strips of relatively high thermal conductivity about the longitudinal axis of said first longitudinal tubular conduit means and with each of said two longitudinally extending strips of relatively high thermal conductivity extending through an angle of about 60.degree. about the longitudinal axis of said first longitudinal tubular conduit means.