US3757860A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Well heating
Assignee: Atlantic Richfield Co
•
Filing: 1972-08-07
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Granted: 1973-09-11
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Expires: 1992-08-07
Abstract
Abstract A method for heating a well to thaw out a frozen portion of the well or to protect permafrost surrounding the well from thermal cycling due to variations in production rate from the well. Also, a method for improving the pumpability of fluid which is produced from a well which does or does not pass through a permafrost zone. Further, a method for preventing the formation of hydrates in a gas well which is in or out of permafrost. In this invention, an alternating current is applied to at least one pipe in the well and maintained at a desired voltage level, the frequency of the alternating current is varied and controlled to cause a skin effect and to increase the effective electrical impedance of said pipe, and an electrical return is established from beneath the portion of the well to be heated, e.g., from beneath a permafrost zone. By this method the pipe is uniformly heated on its outer surface throughout the portion of the well to be heated to a temperature which prevents hydrate formation, or reduces the viscosity of liquid produced through the wellbore, or causes thawing of ice, or prevents freezing of water present to eliminate alternate freezing and thawing of the permafrost and sloughing of permafrost due to such thermal cycling.
Inventors
- 👤 W Pritchett
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 19:44
CPC Classifications
E; E21; E21B; E21B43/00; E21B43/16; E21B43/24; E21B43/2401; Y; Y10; Y10S; Y10S166/00; Y10S166/901
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
97 words
A method of heating at least a portion of a first well in the earth comprising applying to at least one string of pipe in said first well an alternating current, varying the frequency of said alternating current to cause a skin effect and to increase the effective electrical impedance of said pipe to said alternating current to at least about two times that of the normal electrical impedance value of said pipe, controlling said frequency to substantially maintain said impedance increase, and returning said electrical current from beneath said portion of said well to be heated.
Claim 2
Independent Claim
97 words
A method of heating at least a portion of a first well in the earth comprising applying to at least one string of pipe in said first well an alternating current, varying the frequency of said alternating current to cause a skin effect and to increase the effective electrical impedance of said pipe to said alternating current to at least about two times that of the normal electrical impedance value of said pipe, controlling said frequency to substantially maintain said impedance increase, and returning said electrical current from beneath said portion of said well to be heated.
Claim 3
Dependent Claim
38 words
A method according to claim 1 wherein said electrical return is a pipe string in a second well which is spaced from said first well, whereby both said first and second wells are protected at the same time.
Claim 4
Dependent Claim
52 words
A method according to claim 1 wherein said portion of said first well to be heated is in a permafrost zone, said heating is to thaw out said first well from a frozen state or to protect said permafrost from thermal cycling, and returning said electrical current from beneath said permafrost zone.
Claim 5
Dependent Claim
16 words
A method according to claim 3 wherein said voltage is not substantially greater than 75 volts.
Claim 6
Dependent Claim
16 words
A method according to claim 3 wherein said voltage is not substantially greater than 50 volts.
Claim 7
Dependent Claim
20 words
A method according to claim 3 wherein said well is initially frozen up and is thawed out by said method.
Claim 8
Dependent Claim
21 words
A method according to claim 6 wherein said voltage is at least about 75 volts for fast thawing of said well.
Claim 9
Dependent Claim
28 words
A method according to claim 3 wherein said well is not initially frozen up and is protected from freezing up during production of the well by said method.
Claim 10
Dependent Claim
30 words
A method according to claim 3 wherein said well is shut in after drilling of same and without production of same and is protected from freezing up by said method.
Claim 11
Dependent Claim
30 words
A method according to claim 3 wherein said frequency is varied sufficiently to cause said effective electrical resistance to be at least about five times the normal electrical resistance value.
Claim 12
Dependent Claim
17 words
A method according to claim 3 wherein said frequency is at least about 25 cycles per second.
Claim 13
Dependent Claim
19 words
A method according to claim 3 wherein said frequency is from about 25 to about 70 cycles per second.
Claim 14
Dependent Claim
30 words
A method according to claim 1 wherein said frequency is varied sufficiently to cause said effective electrical resistance to be at least about five times the normal electrical resistance value.
Claim 15
Dependent Claim
17 words
A method according to claim 1 wherein said frequency is at least about 25 cycles per second.
Claim 16
Dependent Claim
19 words
A method according to claim 1 wherein said frequency is from about 25 to about 70 cycles per second.
Claim 17
Dependent Claim
64 words
A method according to claim 1 wherein said first well produces natural gas wherein said gas contains hydrate forming water and hydrocarbons, hydrate tends to form in said portion of said first well which is to be heated, said heating being carried out to prevent the formation of hydrates, and returning said electrical current from beneath said hydrate forming portion of said first well.
Claim 18
Dependent Claim
20 words
A method according to claim 16 wherein said hydrate forming portion of said first well is in a permafrost zone.
Claim 19
Dependent Claim
42 words
A method according to claim 16 wherein said hydrate forming portion of said first well is not in a permafrost zone but is at temperature and pressure conditions which promote the formation of hydrate in the gas produced from said first well.
Claim 20
Dependent Claim
16 words
A method according to claim 16 wherein said voltage is not substantially greater than 75 volts.
Claim 21
Dependent Claim
30 words
A method according to claim 16 wherein said frequency is varied sufficiently to cause said effective electrical resistance to be at least about five times the normal electrical resistance value.
Claim 22
Dependent Claim
17 words
A method according to claim 16 wherein said frequency is at least about 25 cycles per second.
Claim 23
Dependent Claim
19 words
A method according to claim 16 wherein said frequency is from about 25 to about 70 cycles per second.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-09-10 | 1977-03-12 | 1977-09-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-10 | 1981-03-12 | 1981-09-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-10 | 1985-03-12 | 1985-09-11 | $7700.00 | Window Closed / Lapsed |