US3745446A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic logging method of locating lost wells
Assignee: Seismograph Service Corp
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Filing: 1972-03-13
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Granted: 1973-07-10
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Expires: 1992-03-13
Abstract
Abstract The top of a buried well casing made of magnetic material is located by logging, in test holes drilled in the vicinity, vertical magnetic logs which show peak magnetic intensity at the depth of the well casing top and horizontal magnetic logs made with vertically spaced magnetometers whose outputs are subtracted to cancel out the effect of the earth''s magnetic field and thus develop peak intensity horizontal lines which, from two or more test holes, intersect at the horizontal location of the well casing. The test holes are drilled and logged successively so as to pinpoint the location of the buried casing. Alternatively, the first derivative signal from the spaced magnetometers comprising the vertical log is scaled to indicate the horizontal distance from the first test hole to the well casing and the second hole is drilled at that distance along the peak intensity horizontal line of the horizontal log.
Inventors
- 👤 W Norris
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 11:22
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/18; G01V3/26
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
212 words
A method of locating the top of a buried well casing made of magnetic material comprising, in combination, the steps of drilling a vertical test hole in the vicinity of said casing, generating a horizontal magnetic log in a horizontal plane from a point down said hole comparing magnetic intensity with angle from a known reference direction, running a vertical magnetic log along said test hole comparing depth against magnetic intensity, plotting the peak intensity on the vertical log and direction of peak intensity on the horizontal log as being indicative of the depth and position of a first horizontal line on which the casing top is located, drilling a second vertical test hole to one side but near said first horizontal line and to the indicated vicinity of the well casing, generating a second horizontal log in a horizontal plane comparing magnetic intensity with angle from a known reference direction, plotting a second horizontal line and its intersection with the first such line as being indicative of the horizontal location of said casing, drilling a third test hole to the indicated location of said well casing top, and repeating said vertical and horizontal logs in said third hole, if necessary, to guide corrective drilling of said third hole into said casing.
Claim 2
Independent Claim
212 words
A method of locating the top of a buried well casing made of magnetic material comprising, in combination, the steps of drilling a vertical test hole in the vicinity of said casing, generating a horizontal magnetic log in a horizontal plane from a point down said hole comparing magnetic intensity with angle from a known reference direction, running a vertical magnetic log along said test hole comparing depth against magnetic intensity, plotting the peak intensity on the vertical log and direction of peak intensity on the horizontal log as being indicative of the depth and position of a first horizontal line on which the casing top is located, drilling a second vertical test hole to one side but near said first horizontal line and to the indicated vicinity of the well casing, generating a second horizontal log in a horizontal plane comparing magnetic intensity with angle from a known reference direction, plotting a second horizontal line and its intersection with the first such line as being indicative of the horizontal location of said casing, drilling a third test hole to the indicated location of said well casing top, and repeating said vertical and horizontal logs in said third hole, if necessary, to guide corrective drilling of said third hole into said casing.
Claim 3
Dependent Claim
39 words
The method of claim 1 in which said horizontal logs are made by subtracting magnetic intensity readings from two vertically spaced horizontally sensing magnetometers so as to cancel out the effect of the ambient magnetic field of the earth.
Claim 4
Dependent Claim
20 words
The method of claim 2 in which said horizontal logs are made by rotating said magnetometers in unison through 360*.
Claim 5
Dependent Claim
51 words
The method of claim 1 in which said horizontal logs are repeated in the same test hole at several depths just above the indicated depth of said well casing top and said horizontal lines are developed as an average of the lines indicated by the logs taken at said several depths.
Claim 6
Independent Claim
190 words
A method of locating the top of a buried well casing made of magnetic material comprising, in combination, the steps of drilling a vertical test hole in the vicinity of said casing, generating a horizontal magnetic log in a horizontal plane from a point down said hole comparing magnetic intensity with angle from a known reference direction, running a vertical magnetic log along said test hole comparing depth against the difference in magnetic intensity readings from two vertically spaced horizontally sensing magnetometers, plotting the direction of peak intensity on the horizontal log as indicative of a horizontal line running from the test hole to the casing top, plotting the peak intensity on the vertical log in terms of the first derivative of magnetic intensity from said spaced magnetometers so as to produce an oppositely shouldered sloping plot line whose midportion is indicative of the depth of the casing top and the spacing of the shoulders is indicative of the distance between the test hole and the casing top, and drilling a second hole at said distance along said horizontal line to said depth so as to drill into said casing.
Claim 7
Independent Claim
190 words
A method of locating the top of a buried well casing made of magnetic material comprising, in combination, the steps of drilling a vertical test hole in the vicinity of said casing, generating a horizontal magnetic log in a horizontal plane from a point down said hole comparing magnetic intensity with angle from a known reference direction, running a vertical magnetic log along said test hole comparing depth against the difference in magnetic intensity readings from two vertically spaced horizontally sensing magnetometers, plotting the direction of peak intensity on the horizontal log as indicative of a horizontal line running from the test hole to the casing top, plotting the peak intensity on the vertical log in terms of the first derivative of magnetic intensity from said spaced magnetometers so as to produce an oppositely shouldered sloping plot line whose midportion is indicative of the depth of the casing top and the spacing of the shoulders is indicative of the distance between the test hole and the casing top, and drilling a second hole at said distance along said horizontal line to said depth so as to drill into said casing.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-07-09 | 1977-01-08 | 1977-07-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-09 | 1981-01-08 | 1981-07-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-09 | 1985-01-08 | 1985-07-10 | $7700.00 | Window Closed / Lapsed |