Patent US4572293A successfully refreshed from Google Patents.
US4572293A
Expired / Lapsed
US
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Method of placing magnetic markers on collarless cased wellbores
Assignee: BP Corp North America Inc
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Filing: 1984-08-31
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Granted: 1986-02-25
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Expires: 2004-08-31
Abstract
Abstract To locate wireline tools in wellbores using collarless or butt joint casing, a magnetic marker is applied at selected positions on the casing before or after placing the casing in a well, such marker being capable of being located by a conventional casing collar locator. Apparatus to apply the marker is also shown.
Inventors
- 👤 James G. Wilson
- 👤 Gerald J. Crawford
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 15:00
CPC Classifications
E; E21; E21B; E21B47/00; E21B47/09; E21B47/092
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
48 words
A method of marking a wellbore casing in a manner such that the mark can be subsequently detected by a casing collar locator comprising placing a horseshoe-shaped electromagnet adjacent said casing and energizing said electromagnet producing a magnetic marker at a location between the poles of the electromagnet.
Claim 2
Independent Claim
48 words
A method of marking a wellbore casing in a manner such that the mark can be subsequently detected by a casing collar locator comprising placing a horseshoe-shaped electromagnet adjacent said casing and energizing said electromagnet producing a magnetic marker at a location between the poles of the electromagnet.
Claim 3
Dependent Claim
22 words
The method of claim 1 wherein the magnetic marker is placed on said casing prior to running said casing in a borehole.
Claim 4
Dependent Claim
23 words
The method of claim 1 wherein the magnetic marker is placed on said casing after said casing is in place in a borehole.
Claim 5
Dependent Claim
15 words
The method of claim 1 where the markers are placed 10 to 100 ft apart.
Claim 6
Dependent Claim
17 words
The method of claim 1 where the magnetic field has a strength of 100 to 200 Gauss.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-02-24 | 1989-08-26 | 1990-02-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-02-24 | 1993-08-26 | 1994-02-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-02-24 | 1997-08-26 | 1998-02-25 | $7700.00 | Window Closed / Lapsed |