US4413679A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Wellbore cathodic protection
Assignee: Phillips Petroleum Co
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Filing: 1982-05-07
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Granted: 1983-11-08
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Expires: 2002-05-07
Abstract
Abstract A method for the cathodic protection of metal conduit in a wellbore in permafrost wherein a predetermined electric current is impressed between said conduit and an anode, the improvement comprising setting said anode in the permafrost away from the wellbore a distance which is greater than the distance between the bottom of the anode and the bottom of the permafrost, and increasing the voltage sufficiently to match the increased resistivity of the permafrost to thereby maintain the predetermined current between the wellbore and anode.
Inventors
- 👤 Thomas K. Perkins
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 03:04
CPC Classifications
E; E21; E21B; E21B41/00; E21B41/02; C; C23; C23F; C23F13/00; C23F13/02; E21B43/00; E21B43/16; E21B43/24; E21B43/2401; Y; Y10; Y10S; Y10S166/00; Y10S166/901
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
161 words
In a method for the cathodic protection of metal conduit in a wellbore, said wellbore being in part in permafrost which has an electrical resistance greater than that of unfrozen earth, wherein said cathodic protection involves impressing a predetermined electrical current by way of a variable voltage in the earth between said conduit and an anode, said anode being set into the earth a finite distance which is less than the depth of the permafrost, said anode being spaced away from said wellbore, the improvement comprising placing said anode a distance away from said wellbore which is greater than the distance between the bottom of said anode and the bottom of said permafrost, and increasing the impressed voltage sufficiently to match the increased resistivity of the permafrost to thereby maintain said predetermined current between said wellbore and anode, whereby at least part of said current between said wellbore and anode passes downwardly through said permafrost into unfrozen earth below the permafrost.
Claim 2
Dependent Claim
161 words
In a method for the cathodic protection of metal conduit in a wellbore, said wellbore being in part in permafrost which has an electrical resistance greater than that of unfrozen earth, wherein said cathodic protection involves impressing a predetermined electrical current by way of a variable voltage in the earth between said conduit and an anode, said anode being set into the earth a finite distance which is less than the depth of the permafrost, said anode being spaced away from said wellbore, the improvement comprising placing said anode a distance away from said wellbore which is greater than the distance between the bottom of said anode and the bottom of said permafrost, and increasing the impressed voltage sufficiently to match the increased resistivity of the permafrost to thereby maintain said predetermined current between said wellbore and anode, whereby at least part of said current between said wellbore and anode passes downwardly through said permafrost into unfrozen earth below the permafrost.
Claim 3
Dependent Claim
38 words
The method according to claim 1 wherein said anode is placed a distance away from said wellbore which is at least about 1.25 times the distance between the bottom of said anode and the bottom of said permafrost.
Claim 4
Dependent Claim
30 words
The method according to claim 1 wherein said voltage is increased to establish and maintain a net current flow between said anode and wellbore of at least about 10 amps.
References Cited (Backward Citations)
US3757860A
Cited
US3766980A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-11-07 | 1987-05-09 | 1987-11-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-11-07 | 1991-05-09 | 1991-11-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-11-07 | 1995-05-09 | 1995-11-08 | $7700.00 | Window Closed / Lapsed |