US3662832A — Insulating a wellbore in permafrost

Claim 1

Independent Claim 209 words

In a method for thermally insulating a region in a wellbore from at least a portion of the wall of the wellbore, said portion of the wall of the wellbore being in permafrost, the improvement comprising providing a single annular cooling zone around at least a portion of said region, said single cooling zone being intermediate said region and said wellbore wall, adding to said single cooling zone a substantially liquid cooling fluid which will vaporize at or below the maximum pressure in said single cooling zone, vaporizing said liquid cooling fluid in said single cooling zone without the use of an expansion device, said vaporization being by absorption of heat from said region thereby preventing said heat from reaching and thawing said permafrost, recovering from said single cooling zone substantially vaporized cooling fluid, condensing said vaporized cooling fluid, returning condensed liquid cooling fluid to said single cooling zone, controlling the recovery pressure of said substantially vaporized cooling fluid to control the vaporization of liquid cooling fluid in said cooling zone, and controlling the amount of liquid cooling fluid in said cooling zone so that the pressure at the bottom of said cooling zone is not so great that said liquid cooling fluid will not vaporize below 32* F.

Claim 2

Dependent Claim 209 words

In a method for thermally insulating a region in a wellbore from at least a portion of the wall of the wellbore, said portion of the wall of the wellbore being in permafrost, the improvement comprising providing a single annular cooling zone around at least a portion of said region, said single cooling zone being intermediate said region and said wellbore wall, adding to said single cooling zone a substantially liquid cooling fluid which will vaporize at or below the maximum pressure in said single cooling zone, vaporizing said liquid cooling fluid in said single cooling zone without the use of an expansion device, said vaporization being by absorption of heat from said region thereby preventing said heat from reaching and thawing said permafrost, recovering from said single cooling zone substantially vaporized cooling fluid, condensing said vaporized cooling fluid, returning condensed liquid cooling fluid to said single cooling zone, controlling the recovery pressure of said substantially vaporized cooling fluid to control the vaporization of liquid cooling fluid in said cooling zone, and controlling the amount of liquid cooling fluid in said cooling zone so that the pressure at the bottom of said cooling zone is not so great that said liquid cooling fluid will not vaporize below 32* F.

Claim 3

Dependent Claim 24 words

A method according to claim 1 wherein said cooling fluid vaporizes at less than 32* F. under a pressure of less than 1,000 psia.

Claim 4

Dependent Claim 43 words

A method according to claim 1 wherein said vaporized cooling fluid is condensed by cooling same, said cooling being effected by contacting said vaporized cooling fluid in a heat exchange relationship without at least one of ambient temperature air and artificially cooled refrigerant.

Claim 5

Dependent Claim 26 words

A method according to claim 3 wherein said condensed cooling fluid gravity feeds without external pumping from the heat exchange zone to said single cooling zone.

Claim 6

Dependent Claim 40 words

A method according to claim 3 wherein before cooling said vaporized cooling fluid said fluid is first compressed to a pressure substantially greater than its recovery pressure so that said fluid will more readily condense at the ambient air temperature.

Claim 7

Dependent Claim 56 words

A method according to claim 5 wherein said cooling fluid is a hydrocarbon having from one to eight, inclusive, carbon atoms per molecule, a mono- or poly-halogenated hydrocarbon having from one to eight, inclusive, carbon atoms per molecule, a mixture of two or more of said hydrocarbons and/or halogenated hydrocarbons, natural gas, CO2, SO2, and NH3.

Claim 8

Dependent Claim 30 words

A method according to claim 5 wherein said recovery pressure is less than about 400 psia and said fluid is compressed to a pressure of at least about 450 psia.

Claim 9

Dependent Claim 49 words

A method according to claim 5 wherein said cooling fluid is a mixture consisting essentially of methane, ethane, propane, butane, and pentane, said recovery pressure is from about 100 to about 400 psia, and said fluid is compressed to a pressure of from about 450 to about 1,000 psia.

Claim 10

Dependent Claim 39 words

A method according to claim 5 wherein said vaporized cooling fluid is cooled by heat exchange contact with ambient temperature air, and said fluid is first compressed only when the temperature of the ambient air exceeds about 20* F.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1975-05-16	1975-11-15	1976-05-16	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1979-05-16	1979-11-15	1980-05-16	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1983-05-16	1983-11-15	1984-05-16	$7700.00	Window Closed / Lapsed

Insulating a wellbore in permafrost

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