Method and apparatus for refrigerating wells by gas expansion

Claim 2

A refrigerated well extending from the surface to an underlying petroleum reservoir for conducting hot fluids through a permafrost zone, which comprises: a closed annular refrigeration chamber defined by inner and outer concentric casings extending a substantial distance into said permafrost zone, said refrigeration chamber lying between said hot fluids conducted through said well and said permafrost; a production tubing within said inner casing to conduct fluids from said underlying petroleum reservoir to the surface, or vice versa; at least one gas expansion nozzle located within said refrigeration chamber and adjacent to the bottom thereof, and discharging into said chamber; gas conduit means to conduct high pressure gas from a source of high pressure gas to said gas expansion nozzle; and means for exhausting low pressure gas from said refrigeration chamber; whereby high pressure gas discharged through said gas expansion nozzle into said refrigeration chamber is cooled to a temperature below the permafrost temperature and flowed upwardly through said refrigeration chamber to prevent the transfer of heat from said hot fluids conducted through said well to the surrounding permafrost.

Claim 3

The apparatus defined in claim 1 wherein said annular refrigeration chamber has a length of about 200 to 700 feet.

Claim 4

The apparatus defined in claim 1 wherein said gas expansion nozzle substantially isentropically expands gas into said refrigeration chamber.

Claim 5

The apparatus defined in claim 1 including a gas separator located at the surface to separate high pressure gas from fluids produced from said underlying petroleum reservoir, wherein said gas conduit means conducts said high pressure gas from said gas separator to said gas expansion nozzle, and wherein said gas conduit means includes a high pressure gas conduit in said refrigeration chamber extending from the surface to said gas expansion nozzle.

Claim 6

The apparatus defined in claim 1 including a downhole gas separator in fluid communication with said production tubing to separate high pressure gas from fluids produced from said underlying petroleum reservoir, said separator being located adjacent to the bottom of said refrigEration chamber, and wherein said gas conduit means conducts high pressure gas from said gas separator to said gas expansion nozzle.

Claim 7

A refrigerated well for conducting hot fluids through a permafrost zone, which comprises: a first casing extending a substantial distance into said permafrost zone and cemented therein; a second casing placed concentrically within said first casing, said second casing extending below said first casing and said second casing being cemented below the bottom of said first casing; sealing means at the top of said first casing to provide a fluid-tight closure between said first and second casings so as to form a closed annular refrigeration chamber; a production tubing within said second casing to convey fluids from an underlying producing strata to the surface, or vice versa, said tubing being insulated through said permafrost zone; at least one gas expansion nozzle located within said refrigeration chamber and adjacent to the bottom thereof, and discharging into said chamber; gas conduit means to conduct high pressure gas from a source of high pressure gas to said gas expansion nozzle; and means for exhausting low pressure gas from said refrigeration chamber.

Claim 8

A refrigerated well for conducting hot fluids through a permafrost zone, which comprises: a first casing extending a substantial distance into said permafrost zone and cemented therein; a second casing placed concentrically within said first casing, said second casing extending below said first casing and said second casing being cemented below the bottom of said first casing; sealing means at the top of said first casing to provide a fluid-tight closure between said first and second casings so as to form a closed annular refrigeration chamber; a production tubing within said second casing to convey fluids from an underlying producing strata to the surface, or vice versa, said tubing being insulated through said permafrost zone; at least one gas expansion nozzle located within said refrigeration chamber and adjacent to the bottom thereof, and discharging into said chamber; gas conduit means to conduct high pressure gas from a source of high pressure gas to said gas expansion nozzle; and means for exhausting low pressure gas from said refrigeration chamber.

Claim 9

The apparatus defined in claim 6 including a gas separator located at the surface to separate high pressure gas from fluids produced from said underlying producing strata, wherein said gas conduit means conducts said high pressure gas from said gas separator to said gas expansion nozzle, and wherein said gas conduit means includes a high pressure gas conduit in said refrigeration chamber extending from the surface to said gas expansion nozzle.

Claim 10

The apparatus defined in claim 6 including a downhole gas separator in fluid communication with said production tubing to separate a portion of the gas from the fluids produced from said underlying producing strata, said separator being located in said second casing adjacent to the bottom of said refrigeration chamber, and wherein said gas conduit means conducts high pressure gas from said gas separator to said gas expansion nozzle.

Claim 11

The apparatus defined in claim 6 wherein said gas expansion nozzle expands the gas passing therethrough substantially isentropically.

Claim 12

The apparatus defined in claim 6 including a production casing placed concentrically within said second casing, said production casing extending from the surface to said underlying producing strata and said production casing being cemented below the bottom of said second casing.

Claim 13

The apparatus defined in claim 6 wherein said second casing extends at least to the bottom of said permafrost zone.

Claim 14

A refrigerated well for conducting hot fluids through a permafrost zone, which comprises: a surface conductor cemented in the permafrost; a first casing placed concentrically within said surface conductor and extending about 200 to 700 feet into said permafrost zone, said first casing being cemented to the surface; a second casing placed concentrically within said first casing, said second casing extending at least through said permafrost zone and said second casing being cemented below the bottom of said first casing; sealing means at the top of said first casing to provide a fluid-tight closure between said first and second casings so as to form a closed annular refrigeration chamber; a production casing placed concentrically within said second casing and extending from the surface to an underlying petroleum reservoir, said production casing being cemented below the bottom of said second casing; a production tubing within said production casing to convey fluids from an underlying petroleum reservoir to the surface, or vice versa, said tubing being insulated through said permafrost zone; at least one gas expansion nozzle located with said refrigeration chamber and adjacent to the bottom thereof, to substantially isentropically expand high pressure gas into said chamber; a gaS conduit in said refrigeration chamber to conduct high pressure gas from the surface to said gas expansion nozzle; and means to exhaust low pressure gas from said refrigeration chamber.

Claim 15

A refrigerated well for conducting hot fluids through a permafrost zone, which comprises: a surface conductor cemented in the permafrost; a first casing placed concentrically within said surface conductor and extending about 200 to 700 feet into said permafrost zone, said first casing being cemented to the surface; a second casing placed concentrically within said first casing, said second casing extending at least through said permafrost zone and said second casing being cemented below the bottom of said first casing; sealing means at the top of said first casing to provide a fluid-tight closure between said first and second casings so as to form a closed annular refrigeration chamber; a production casing placed concentrically within said second casing and extending from the surface to an underlying petroleum reservoir, said production casing being cemented below the bottom of said second casing; a production tubing within said production casing to convey fluids from an underlying petroleum reservoir to the surface, or vice versa, said tubing being insulated through said permafrost zone; at least one gas expansion nozzle located with said refrigeration chamber and adjacent to the bottom thereof, to substantially isentropically expand high pressure gas into said chamber; a gaS conduit in said refrigeration chamber to conduct high pressure gas from the surface to said gas expansion nozzle; and means to exhaust low pressure gas from said refrigeration chamber.

Claim 16

A refrigerated well penetrating a permafrost zone for producing hot fluids from an underlying petroleum reservoir, which comprises: a surface conductor cemented in the permafrost; a first casing placed concentrically within said surface conductor and extending about 200 to 700 feet into said permafrost zone, said first casing being cemented to the surface; a second casing placed concentrically within said first casing, said second casing extending at least through said permafrost zone and said second casing being cemented below the bottom of said first casing; sealing means at the top of said first casing to provide a fluid-tight closure between said first and second casings so as to form a closed annular refrigeration chamber; a production casing placed concentrically within said second casing and extending from the surface to an underlying petroleum reservoir, said production casing being cemented below the bottom of said second casing; a production tubing within said production casing to convey fluids from said underlying petroleum reservoir to the surface, said tubing being insulated through the permafrost zone; a downhole gas separator in said production casing adjacent to the bottom of said refrigeration chamber to receive produced fluids flowing upwardly through said production tubing, disengage a portion of the gas from said produced fluids, and discharge the residual produced fluids up said production tubing; at least one gas expansion nozzle located within said refrigeration chamber and adjacent to the bottom thereof, to substantially isentropically expand high pressure gas into said chamber; gas conduit means to conduct gas from said downhole gas separator to said gas expansion nozzle; and means to exhaust low pressure gas from said refrigeration chamber.

Claim 17

A refrigerated well penetrating a permafrost zone for producing hot fluids from an underlying petroleum reservoir, which comprises: a surface conductor cemented in the permafrost; a first casing placed concentrically within said surface conductor and extending about 200 to 700 feet into said permafrost zone, said first casing being cemented to the surface; a second casing placed concentrically within said first casing, said second casing extending at least through said permafrost zone and said second casing being cemented below the bottom of said first casing; sealing means at the top of said first casing to provide a fluid-tight closure between said first and second casings so as to form a closed annular refrigeration chamber; a production casing placed concentrically within said second casing and extending from the surface to an underlying petroleum reservoir, said production casing being cemented below the bottom of said second casing; a production tubing within said production casing to convey fluids from said underlying petroleum reservoir to the surface, said tubing being insulated through the permafrost zone; a downhole gas separator in said production casing adjacent to the bottom of said refrigeration chamber to receive produced fluids flowing upwardly through said production tubing, disengage a portion of the gas from said produced fluids, and discharge the residual produced fluids up said production tubing; at least one gas expansion nozzle located within said refrigeration chamber and adjacent to the bottom thereof, to substantially isentropically expand high pressure gas into said chamber; gas conduit means to conduct gas from said downhole gas separator to said gas expansion nozzle; and means to exhaust low pressure gas from said refrigeration chamber.

Claim 18

The apparatus defined in claim 13 wherein said gas conduit means includes (1) first and second packers set in the annulus between said production tubing and said production casing, above and below said downhole gas separator, respectively, to define an enclosed annular first chamber; (2) third and fourth packers set in the annulus between said production casing and said second casing to define an enclosed second annular chamber surrounding said first annular chamber; (3) an aperture in said production casing communicating said first and second annular chambers; and (4) a conduit communicating said second annular chamber to the inlet of said gas expansion nozzle.

Claim 19

The apparatus defined in claim 14 wherein said downhole separator includes (1) an outer cylindrical shell having an inlet at its bottom and an outlet at its top for connection, respectively, to said production tubing; (2) an internal standpipe extending above said inlet; (3) an inverted cap extending downwardly below the lip of said standpipe; (4) an inverted cup-shaped diverter supported immediately above said standpipe; (5) an apertured baffle separating said cap into a lower section and an upper gas chamber; and (6) a float-type valve in said gas chamber having an outlet connected to the exterior of said cylindrical shell.

Claim 22

The method defined in claim 16 wherein said high pressure gas is produced gas separated from fluids produced from a petroleum reservoir.

Claim 23

The method defined in claim 16 wherein said high pressure gas is substantially isentropically expanded into said refrigeration chamber.

Claim 24

The method defined in claim 16 wherein said low temperature gas is withdrawn from said refrigeration chamber at a temperature below about 32* F.