US3642065A - Process for maintaining thermal conductivity of insulation in permafrost completion - Google Patents

Process for maintaining thermal conductivity of insulation in permafrost completion Download PDF

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US3642065A
US3642065A US57637A US3642065DA US3642065A US 3642065 A US3642065 A US 3642065A US 57637 A US57637 A US 57637A US 3642065D A US3642065D A US 3642065DA US 3642065 A US3642065 A US 3642065A
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annulus
insulation
permafrost
air
fluid
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Elmo M Blount
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ExxonMobil Oil Corp
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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B36/00—Heating, cooling or insulating arrangements for boreholes or wells, e.g. for use in permafrost zones
    • E21B36/003—Insulating arrangements
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S166/00—Wells
    • Y10S166/901—Wells in frozen terrain

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  • ABSTRACT This specification discloses a process of completing a well penetrating a permafrost zone of the earth whereby the lowthermal conductivity is maintained of foam insulation installed in the well.
  • the insulation is surrounded by gas having a lower thermal conductivity than air.
  • This invention relates to methods for completing wells drilled through permafrost zones of the earth. More particularly, this invention relates to methods for preventing the deterioration of the thermal conductivity of foam insulation used in wells completed in the permafrost.
  • Various techniques may be used in completing wells drilled through permafrost zones.
  • One such technique involves the use of one or more shear pin slip joints in the upper part of the permafrost casing string. This completion technique does not avoid melting the permafrost but rather permits the slip joint 1 in the permafrost string to telescope upon melting of the permafrost and concurring ground, subsidence, thereby avoiding stresses in the permafrost string.
  • Another technique involves the use of a vacuum bottle arrangement. Two short lengths of concentric pipe sections are sealed to form a closed annulus and refrigeration coils are welded to the outside of the larger pipe. A vacuum is pulled on the annulus and the apparatus lowered in the well. Refrigeration is used as needed to keep the permafrost from thawing.
  • Another possible technique involves the use of insulated tubing.
  • the outside of the production tubing string may be wrapped with insulation before it is run into the well.
  • FIGURE is a vertical section of a well penetrating the earth and illustrates an embodiment of this invention.
  • This invention relates to a method of completing a well drilled through the permafrost zone of the earth.
  • a foam insulation formed by blowing with a gas having a lower thermal conductivity than air is present in an air-filled annulus intermediate concentric strings of casing in the well and adjacent the permafrost.
  • the annulus is sealed below the insulation.
  • a fluid that has a vapor pressure greater than atmospheric at permafrost temperatures, and when vaporized has a lower thermal conductivity than air, is injected into the annulus. Air is removed from the annulus and the annulus is filled with vapors of the fluid. Thereafter the annulus is sealed at an upper location to provide a fluidtight annulus filled with vapors of the fluid surrounding the insulation.
  • Foams which have been blown with a gas having a lower thermal conductivity than air during their formation have been found to serve very effectively as insulation.
  • a foam is polyurethane foam in either molded or extruded form. Molded polyurethane foam is preferred however for several reasons. It is more convenient to install in the wells and any optimum shape and length can be obtained. Also, a high density, relatively impermeable skin can be obtained on the molded section and the individual pieces are less subject to damage while handling and running into the hole.
  • thermal conductivity in general and of thermal conductivity of a foam follows.
  • the thermal conductivity (k) is defined as the amount of heat transferred per unit time between two parallel plates at different temperatures.
  • equation l illustrates the use of k in thermal calculations:
  • T the temperature of the plates or surfaces
  • k the conductivity, and can be in any unit as required to provide the dimensional integrity of the equation.
  • the units of k are generally Btu-in/ft hr F.
  • the effective k of a foam is actually the result or sum of more than one form of heat transfer as defined by equation (2) below:
  • the conduction through the solid material (k,) is insignificant.
  • the convection in the vapor in the individual cells (k is influenced by the size and shape of the cells. Reducing the size of the individual cells reduces the convection in the vapor in the individual cells (k and also decreases the effect of radiation (k,) by causing more interfaces to be in the path of heat flow.
  • the gas conductivity (k,) is apparently the predominant parameter influencing the overall k of the foam.
  • the foam is about 96 percent vapor.
  • Polyurethane is formed by blowing with trichloromonofluoromethane (Freon-l l).
  • the foam is formed of many individual cells having Freon-ll trapped therein and having a partial pressure something less than 1.0 atmosphere.
  • the cell walls are relatively impermeable to Freon-l l and relatively permeable to air.
  • the thermal conductivity (k) of Freon-l1 is about 0.06 B.t.u.-in./ft. hr. F. while the k of air is about 0.17 B.t.u.-in./ft.'*'hr. F.
  • foam When foam is installed as insulation in an air-filled annulus, air diffuses into the individual cells and thus reduces the thermal conductivity of the insulation. In accordance with this invention this reduction in thermal conductivity is alleviated by replacing the air surrounding the foam with a gas having a lower thermal conductivity than air.
  • Insulation 21 is shown in annulus 19 intermediate production string 15 and surface string 11, and adjacent permafrost 1.
  • Annulus 19 is sealed below insulation 21 by, for example, a packer associated with casing hanger 14. Accumulated liquid is removed from annulus 19, leaving it air filled and essentially dry.
  • Annulus 19 is sealed at an upper location by casinghead 38.
  • Fluid 40 having a vapor pressure greater than atmospheric at permafrost temperatures, which fluid when vaporized has a lower thermal conductivity than air, is injected into annulus 19.
  • Such a fluid is dichlorodifluoromethane (Freon-12).
  • Fluid 40 may be injected as liquid from drum 24 via conduit 26, valve 28, pipe 30, valve 32 through surface string 11 and into annulus 19 where it flows to the bottom thereof. A sufficient amount of fluid 40 is injected into annulus 19 such that when all of the liquid is vaporized except an infinitesimal amount, annulus 19 is completely filled with vapors of the liquid at a pressure ofno greater than p.s.i.g.
  • Valve 34 associated with casinghead 38, may be used to facilitate the removal of air from annulus 19.
  • fluid 40 vaporizes in annulus 19
  • the air in annulus 19 is displaced from annulus 19 through open valve 34.
  • Fluid 40 has a higher molecular weight than air and thus the vapors thereof have a higher density than air.
  • annulus 19 is filled by such vapors and air is displaced from the annulus through valve 34.
  • valve 34 is closed, leaving the insulation 21 surrounded by the vapors of fluid 40.
  • Thepressure in annulus 19 should be maintained below the maximum allowable structure pressure of the foam insulation.
  • the maximum allowable structure pressure is the pressure which if exceeded results in damage to the cell walls of the insulation. For 2 pounds per cubic foot density polyurethane insulation this pressure is 10 p.s.i.g. at 32F. and for 4 pounds per cubic foot density polyurethane insulation this pressure is 40 p.s.i.g. at 32 F.
  • the limiting factor ofthe maximum allowable structure pressure, 10 p.s.i.g. pressure at 32 F. (for 2 lb./ft. foam) or 40 p.s.i.g. at 32 F. (for 4 lb./ft. foam) can be met by choosing a fluid which has a vapor pressure at 32 F.
  • Freon-l2 (CC1 F can be used if the surface is vented through a relief valve. Mixtures of these and other freon compounds having the desired characteristics may be used, as well as other gases such as ethane, propane, butane, and mixtures of hydrocarbon gases up to pentane.
  • the temperature of the annulus may be determined by observing the pressure of annulus 19 and referring to the phase diagram. A rise in temperature as might be caused by breakdown of insulation 21 allowing annulus 19 to heat up above 32 F. can be noted directly by observing a corresponding rise in the pressure of annulus 19.
  • a well may be provided for carrying out this invention by drilling a large diameter hole into permafrost zone 1 and lowering conductor pipe 3 into the hole and cementing it thereto by cement 5.
  • the hole is then extended and a permafrost string 7 is lowered into the hole.
  • the lower portion of permafrost string 7 is cemented by cement 9.
  • the hole is extended further into the earth and a surface string 11 is lowered thereinto and cemented by cement 13.
  • the hole is drilled to total depth and a production string 15 is lowered thereinto and cemented by cement 17.
  • Production string 15 is hung in surface string 11 by casing hanger 14.
  • a circulating valve 16 is installed in production string 15 above hanger 14 and a backoff joint 18 is installed above circulating valve 16.
  • circulating valve 16 is opened to provide a passage between the interior of production string 1 1 and annulus l9 and liquid is used to circulate out the excess cement from annulus 19 above hanger 14, leaving annulus l9 and production string 15 liquid filled. This leaves annulus l9 and backoff joint 18 above circulating valve 16 free of cement. Accumulated liquid is withdrawn from annulus 19 adjacent the permafrost and intermediate production string 15 and surface string 11, leaving annulus 19 dry and air filled. This accumulated liquid may be withdrawn by swabbing the interior of production string 15 while circulating valve 16 is open, thereby removing the accumulated liquid from both the interior of production string 15 and annulus 19 adjacent the permafrost zone 1. Circulating valve 16 is then closed.
  • a particular method of installing insulation involves backing off production string 15 at backoff joint 18 and removing the production string 15 from the well. Insulation is then installed at the surface, about a portion of the production string removed from the well, and thereafter the insulated string is lowered into the well and reconnected to the lower portion of production string 15. The insulation is thereby installed in the dry annulus. It is very important that the insulation be installed in a dry annulus and that insulation be kept dry because liquid causes distortion of the insulation and greatly reduces its insulating value.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Geology (AREA)
  • Mining & Mineral Resources (AREA)
  • Physics & Mathematics (AREA)
  • Environmental & Geological Engineering (AREA)
  • Fluid Mechanics (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
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Abstract

This specification discloses a process of completing a well penetrating a permafrost zone of the earth whereby the lowthermal conductivity is maintained of foam insulation installed in the well. The insulation is surrounded by gas having a lower thermal conductivity than air.

Description

United States Patent Blount [54] PROCESS FOR MAINTAINING THERMAL CONDUCTIVITY OF INSULATION IN PERMAFROST COMPLETION [72] Inventor: Elmo M. Blount, Irving, Tex.
[73] Assignee: Mobil Oil Corporation [22] Filed: July 23, 1970 211 Appl. No.1 57,637
[52] U.S.Cl ..l66/244 R, 166/D1G. 1 [51] Int. Cl ..E2lb 43/00 [58] FieldofSearch ..l66/244,57,315,303,D1G. 1;
138/149, DIG. 9,113
[56] Rel'erences Cited UNITED STATES PATENTS 3,280,909 10/1966 Closmann et a1. ..166/272 X 3,380,530 4/1968 McConnell et a1... ..l 66/57 X 3,397,745 8/1968 Owens et al. ..166/57 3,456,735 7/1969 McDougall et al... 166/57 UX 3,478,783 11/1969 Doyle 166/57 UX 3,511,282 5/1970 Willhite et a1. ..138/113 3,525,399 8/1970 Bayless et a1 ........1 6 6/57 X 1 1 Feb. 15, 1972 FOREIGN PATENTS OR APPLICATIONS 134,205 9/1966 u.s.s.R, ..166/D1G.1
OTHER PUBLlCATlONS Experts are Tackling the Permafrost, 0118 4 6215 in't'r- I national, Vol 10, No. 8, Aug. 1970, pp 84, 89 and 90. 166-Dig. l Dupont Brochure, fRigid Urethane Foam made with DuPont Hylene Organic lsocyanates, E. l. du-
;. P ut..flsflsmaqri-Qsafiflmm sm? ELI? "952; PP-
1-7. 1387Cllular Digest World Oil, Alaskan Comple tions will be Complicated, Jan. 1970, page 85. 166-Dig. l
1 Primary ExaminerStephen J. Novosad Att0rneyWilliam J. Scherback, Frederick E. Dumoulin, William D. Jackson, Henry L. Ehrlich, Andrew L. Gaboriault and Sidney A. Johnson [57] ABSTRACT This specification discloses a process of completing a well penetrating a permafrost zone of the earth whereby the lowthermal conductivity is maintained of foam insulation installed in the well. The insulation is surrounded by gas having a lower thermal conductivity than air.
.. lqla mal Drawiaslfisw a PATENTEDFEB 15 I972 ELMO M. BLOUNT INVENTjOR yfl E: n m M E V V 1 H H z: =52 "X24, m W
ATTORNEY PROCESS FOR MAINTAINING THERMAL CONDUCTIVITY OF INSULATION IN PERMAFROST COMPLETION BACKGROUND OF THE INVENTION This invention relates to methods for completing wells drilled through permafrost zones of the earth. More particularly, this invention relates to methods for preventing the deterioration of the thermal conductivity of foam insulation used in wells completed in the permafrost.
Problems have been encountered in completing wells drilled in areas where permafrost exists, namely, on the North Slope of Alaska and Northern Canada. One such problem is the tendency of the permafrost around the producing wells to melt. Melting of the permafrost would leave unsupported long strings of easing. Such melting would also cause subsidence of the permafrost zone in the vicinity of the well and subsidence of the surface, thereby damaging surface installations.
Various techniques may be used in completing wells drilled through permafrost zones. One such technique involves the use of one or more shear pin slip joints in the upper part of the permafrost casing string. This completion technique does not avoid melting the permafrost but rather permits the slip joint 1 in the permafrost string to telescope upon melting of the permafrost and concurring ground, subsidence, thereby avoiding stresses in the permafrost string.
Another technique involves the use of a vacuum bottle arrangement. Two short lengths of concentric pipe sections are sealed to form a closed annulus and refrigeration coils are welded to the outside of the larger pipe. A vacuum is pulled on the annulus and the apparatus lowered in the well. Refrigeration is used as needed to keep the permafrost from thawing.
Another possible technique involves the use of insulated tubing. For example, the outside of the production tubing string may be wrapped with insulation before it is run into the well.
SUMMARY OF THE INVENTION In accordance with the present invention there are provided new and improved techniques for completing a well penetrating a permafrost zone of the earth wherein foam insulation formed by blowing with a gas having a lower thermal conductivity than air is used-to insulate the produced fluids from the permafrost zone. This insulation is present in an air-filled annulus adjacent the permafrost intermediate concentric strings of casing. The annulus is sealed below the insulation. A fluid having a vapor pressure greater than atmospheric at permafrost temperatures and which fluid when vaporized has a lower thermal conductivity than air is injected into the annulus. The air is removed from the annulus, leaving it filled with vapors of the fluid and the annulus is sealed at an upper location to provide a fluidtight annulus filled with vapors of the fluid surrounding the insulation.
BRIEF DESCRIPTION OF THE DRAWING The FIGURE is a vertical section of a well penetrating the earth and illustrates an embodiment of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS This invention relates to a method of completing a well drilled through the permafrost zone of the earth. A foam insulation formed by blowing with a gas having a lower thermal conductivity than air is present in an air-filled annulus intermediate concentric strings of casing in the well and adjacent the permafrost. The annulus is sealed below the insulation. A fluid that has a vapor pressure greater than atmospheric at permafrost temperatures, and when vaporized has a lower thermal conductivity than air, is injected into the annulus. Air is removed from the annulus and the annulus is filled with vapors of the fluid. Thereafter the annulus is sealed at an upper location to provide a fluidtight annulus filled with vapors of the fluid surrounding the insulation.
Foams which have been blown with a gas having a lower thermal conductivity than air during their formation have been found to serve very effectively as insulation. Such a foam is polyurethane foam in either molded or extruded form. Molded polyurethane foam is preferred however for several reasons. It is more convenient to install in the wells and any optimum shape and length can be obtained. Also, a high density, relatively impermeable skin can be obtained on the molded section and the individual pieces are less subject to damage while handling and running into the hole.
The thermal conductivity of foam fonned by blowing with a gas having a lower thermal conductivity than air deteriorates somewhat with age. I have discovered a process whereby such deterioration is alleviated for a foam installed in an air-filled annulus in a well.
To better understand this invention a brief discussion of thermal conductivity in general and of thermal conductivity of a foam follows. The thermal conductivity (k) is defined as the amount of heat transferred per unit time between two parallel plates at different temperatures. The following equation l illustrates the use of k in thermal calculations:
where Q= the quantity of heat;
A the cross-sectional area;
T= the temperature of the plates or surfaces;
L= the distance between the surfaces;
At= the increment of time;
k the conductivity, and can be in any unit as required to provide the dimensional integrity of the equation. For foam the units of k are generally Btu-in/ft hr F.
The effective k of a foam is actually the result or sum of more than one form of heat transfer as defined by equation (2) below:
k, the contribution to the overall conductivity due to conduction through the solid material;
k, the contribution to the conductivity of the gasin the cells;
k the contribution due to convection of the gas in the cells; and
k,. the contribution due to radiation.
The conduction through the solid material (k,) is insignificant. The convection in the vapor in the individual cells (k is influenced by the size and shape of the cells. Reducing the size of the individual cells reduces the convection in the vapor in the individual cells (k and also decreases the effect of radiation (k,) by causing more interfaces to be in the path of heat flow. The gas conductivity (k,) is apparently the predominant parameter influencing the overall k of the foam. The foam is about 96 percent vapor.
Polyurethane is formed by blowing with trichloromonofluoromethane (Freon-l l). The foam is formed of many individual cells having Freon-ll trapped therein and having a partial pressure something less than 1.0 atmosphere. The cell walls are relatively impermeable to Freon-l l and relatively permeable to air. The thermal conductivity (k) of Freon-l1 is about 0.06 B.t.u.-in./ft. hr. F. while the k of air is about 0.17 B.t.u.-in./ft.'*'hr. F. When foam is installed as insulation in an air-filled annulus, air diffuses into the individual cells and thus reduces the thermal conductivity of the insulation. In accordance with this invention this reduction in thermal conductivity is alleviated by replacing the air surrounding the foam with a gas having a lower thermal conductivity than air.
Referring to the drawing there is illustrated a particular well in which the invention may be practiced. Insulation 21 is shown in annulus 19 intermediate production string 15 and surface string 11, and adjacent permafrost 1. Annulus 19 is sealed below insulation 21 by, for example, a packer associated with casing hanger 14. Accumulated liquid is removed from annulus 19, leaving it air filled and essentially dry. Annulus 19 is sealed at an upper location by casinghead 38. Fluid 40, having a vapor pressure greater than atmospheric at permafrost temperatures, which fluid when vaporized has a lower thermal conductivity than air, is injected into annulus 19. Such a fluid is dichlorodifluoromethane (Freon-12).
Fluid 40 may be injected as liquid from drum 24 via conduit 26, valve 28, pipe 30, valve 32 through surface string 11 and into annulus 19 where it flows to the bottom thereof. A sufficient amount of fluid 40 is injected into annulus 19 such that when all of the liquid is vaporized except an infinitesimal amount, annulus 19 is completely filled with vapors of the liquid at a pressure ofno greater than p.s.i.g.
Valve 34, associated with casinghead 38, may be used to facilitate the removal of air from annulus 19. As fluid 40 vaporizes in annulus 19, the air in annulus 19 is displaced from annulus 19 through open valve 34. Fluid 40 has a higher molecular weight than air and thus the vapors thereof have a higher density than air. Thus, as fluid 40 in annulus 19 vaporizes, annulus 19 is filled by such vapors and air is displaced from the annulus through valve 34. After the annulus is essentially vapor filled, valve 34 is closed, leaving the insulation 21 surrounded by the vapors of fluid 40.
Thepressure in annulus 19 should be maintained below the maximum allowable structure pressure of the foam insulation. The maximum allowable structure pressure is the pressure which if exceeded results in damage to the cell walls of the insulation. For 2 pounds per cubic foot density polyurethane insulation this pressure is 10 p.s.i.g. at 32F. and for 4 pounds per cubic foot density polyurethane insulation this pressure is 40 p.s.i.g. at 32 F. The limiting factor ofthe maximum allowable structure pressure, 10 p.s.i.g. pressure at 32 F. (for 2 lb./ft. foam) or 40 p.s.i.g. at 32 F. (for 4 lb./ft. foam), can be met by choosing a fluid which has a vapor pressure at 32 F. no greater than the maximum allowed pressure. Alternatively, if the fluid exhibits a vapor pressure that is greater than the maximum allowable pressure, the excess pressure may be vented at the surface by a relief valve 36 to keep the pressure in annulus 19 below the maximum allowable pressure. The vapor pressure must be above atmospheric in order to displace the air from the annulus 19 but less than the maximum allowable structure pressure for the particular insulation used in order to prevent damage to the insulation. Thus, a fluid having these properties, and in addition, the properties of a lower thermal conductivity than air, may be chosen for injecting into annulus l9. Octafluorocyclobutane, Freon C-3l8 (C F cyclic), is such a fluid. Freon-l2 (CC1 F can be used if the surface is vented through a relief valve. Mixtures of these and other freon compounds having the desired characteristics may be used, as well as other gases such as ethane, propane, butane, and mixtures of hydrocarbon gases up to pentane.
When using a fluid having a known pressure-temperature phase diagram, the temperature of the annulus may be determined by observing the pressure of annulus 19 and referring to the phase diagram. A rise in temperature as might be caused by breakdown of insulation 21 allowing annulus 19 to heat up above 32 F. can be noted directly by observing a corresponding rise in the pressure of annulus 19.
A well may be provided for carrying out this invention by drilling a large diameter hole into permafrost zone 1 and lowering conductor pipe 3 into the hole and cementing it thereto by cement 5. The hole is then extended and a permafrost string 7 is lowered into the hole. The lower portion of permafrost string 7 is cemented by cement 9. The hole is extended further into the earth and a surface string 11 is lowered thereinto and cemented by cement 13. Thereafter, the hole is drilled to total depth and a production string 15 is lowered thereinto and cemented by cement 17. Production string 15 is hung in surface string 11 by casing hanger 14. A circulating valve 16 is installed in production string 15 above hanger 14 and a backoff joint 18 is installed above circulating valve 16. After placing cement 17 intermediate production string 15 and surface string 11, circulating valve 16 is opened to provide a passage between the interior of production string 1 1 and annulus l9 and liquid is used to circulate out the excess cement from annulus 19 above hanger 14, leaving annulus l9 and production string 15 liquid filled. This leaves annulus l9 and backoff joint 18 above circulating valve 16 free of cement. Accumulated liquid is withdrawn from annulus 19 adjacent the permafrost and intermediate production string 15 and surface string 11, leaving annulus 19 dry and air filled. This accumulated liquid may be withdrawn by swabbing the interior of production string 15 while circulating valve 16 is open, thereby removing the accumulated liquid from both the interior of production string 15 and annulus 19 adjacent the permafrost zone 1. Circulating valve 16 is then closed.
A particular method of installing insulation involves backing off production string 15 at backoff joint 18 and removing the production string 15 from the well. Insulation is then installed at the surface, about a portion of the production string removed from the well, and thereafter the insulated string is lowered into the well and reconnected to the lower portion of production string 15. The insulation is thereby installed in the dry annulus. It is very important that the insulation be installed in a dry annulus and that insulation be kept dry because liquid causes distortion of the insulation and greatly reduces its insulating value.
What is claimed is:
1. In a process of completing a well penetrating a permafrost zone of the earth wherein foam insulation formed by blowing with a gas having a lower thermal conductivity than air is present in an air-filled annulus adjacent the permafrost intermediate concentric strings of casing in said well, said annulus being sealed below said insulation, the steps comprising:
a. injecting into said annulus a fluid having a vapor pressure greater than atmospheric at permafrost temperatures, said fluid when vaporized having a lower thermal conductivity than air;
b. removing air from said annulus whereby said annulus is filled by vapors of said fluid; and
c. sealing said annulus at an upper location to provide a fluidtight annulus filled with said vapors of said fluid surrounding said insulation.
2. The process of claim 1 wherein said fluid has a vapor pressure of less than the maximum allowable structure pressure at 32 F.
3. The process of claim 1 wherein said fluid has a vapor pressure of about 5 p.s.i.g. at 32 F.
4. The processof claim 1 wherein said fluid is octafluorocyclobutane.
5. The process of claim 1 wherein air is displaced from said annulus by said vapors.
6. The process of claim 1 further comprising venting said annulus to maintain a pressure of no greater than the maximum allowable structure pressure in said annulus.
7. The process of claim 6 wherein said fluid is dichlorodifluoromethane.

Claims (6)

  1. 2. The process of claim 1 wherein said fluid has a vapor pressure of less than the maximum allowable structure pressure at 32* F.
  2. 3. The process of claim 1 wherein said fluid has a vapor pressure of about 5 p.s.i.g. at 32* F.
  3. 4. The process of claim 1 wherein said fluid is octafluorocyclobutane.
  4. 5. The process of claim 1 wherein air is displaced from said annulus by said vapors.
  5. 6. The process of claim 1 further comprising venting said annulus to maintain a pressure of no greater than the maximum allowable structure pressure in said annulus.
  6. 7. The process of claim 6 wherein said fluid is dichlorodifluoromethane.
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3720267A (en) * 1970-10-02 1973-03-13 Atlantic Richfield Co Well production method for permafrost zones
US3727703A (en) * 1971-10-22 1973-04-17 Chevron Res Well circulation fluid for use in permafrost
US3766985A (en) * 1971-12-01 1973-10-23 Univ Kansas State Production of oil from well cased in permafrost
US3851704A (en) * 1973-06-28 1974-12-03 Continental Oil Co Method for insulating a borehole
US4528104A (en) * 1982-08-19 1985-07-09 Nl Industries, Inc. Oil based packer fluids

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US3397745A (en) * 1966-03-08 1968-08-20 Carl Owens Vacuum-insulated steam-injection system for oil wells
US3456735A (en) * 1967-02-01 1969-07-22 Exxon Production Research Co Method for completing wells to prevent paraffin deposits
US3478783A (en) * 1967-03-27 1969-11-18 Robert Redford Doyle Thermally insulated piping system
US3511282A (en) * 1966-02-07 1970-05-12 Continental Oil Co Prestressed conduit for heated fluids
US3525399A (en) * 1968-08-23 1970-08-25 Exxon Production Research Co Technique for insulating a wellbore with silicate foam

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US3280909A (en) * 1964-01-20 1966-10-25 Shell Oil Co Method of producing an oil bearing formation
US3511282A (en) * 1966-02-07 1970-05-12 Continental Oil Co Prestressed conduit for heated fluids
US3511282B1 (en) * 1966-02-07 1987-10-13
US3397745A (en) * 1966-03-08 1968-08-20 Carl Owens Vacuum-insulated steam-injection system for oil wells
US3380530A (en) * 1966-04-01 1968-04-30 Malcolm F. Mcconnell Steam stimulation of oil-bearing formations
US3456735A (en) * 1967-02-01 1969-07-22 Exxon Production Research Co Method for completing wells to prevent paraffin deposits
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Publication number Priority date Publication date Assignee Title
US3720267A (en) * 1970-10-02 1973-03-13 Atlantic Richfield Co Well production method for permafrost zones
US3727703A (en) * 1971-10-22 1973-04-17 Chevron Res Well circulation fluid for use in permafrost
US3766985A (en) * 1971-12-01 1973-10-23 Univ Kansas State Production of oil from well cased in permafrost
US3851704A (en) * 1973-06-28 1974-12-03 Continental Oil Co Method for insulating a borehole
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