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US3748574A
Expired / Lapsed
US
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Method for determining the distance between a cased and an open well
Assignee: Shell USA Inc
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Filing: 1972-01-27
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Granted: 1973-07-24
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Expires: 1992-01-27
Abstract
Abstract A method for determining the distance between a cased well and an open well using resistivity measurements made in the open well using long electrode spacings and a resistivity is calculated from data that is not influenced by the casing in the cased well. A calculation is made of the anticipated reduction in the resistivity measurements caused by the presence of the casing using the calculated resistivity and assuming varying distances between the cased well and the point at which the resistivity is measured. A nomograph is prepared by plotting the calculated reduction versus the assumed distances for each calculated formation resistivity. The measured resistivity is used to determine the actual reduction in the resistivity caused by the casing and the distance between the two wells is then obtained from the nomograph.
Inventors
- 👤 F Mitchell
- 👤 J Vogiatzis
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 16:56
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/18; G01V3/20
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
164 words
A method for determining the distance between a cased well and an open well comprising: determing from prior measurements the normal formation resistivity that would be measured in the open well at various depth points in the absence of the cased well; calculating by a machine process, using the resistivity of the casing, the determined normal formation resistivity and assumed distances between the two wells, the reduction in the normal resistivity resulting from the presence of the casing for each of the assumed distances; producing a nomograph by plotting the calculated reduction in the normal resistivity with respect to the assumed distances between the two wells; measuring the resistivity in the open well at various depth points; determining the difference between the previously determined normal resistivity and the measured resistivity at said various depth points to obtain the actual reduction in normal resistivity; and using the actual reduction in the normal resistivity and nomogram to obtain the distance between the open and cased wells.
Claim 2
Independent Claim
164 words
A method for determining the distance between a cased well and an open well comprising: determing from prior measurements the normal formation resistivity that would be measured in the open well at various depth points in the absence of the cased well; calculating by a machine process, using the resistivity of the casing, the determined normal formation resistivity and assumed distances between the two wells, the reduction in the normal resistivity resulting from the presence of the casing for each of the assumed distances; producing a nomograph by plotting the calculated reduction in the normal resistivity with respect to the assumed distances between the two wells; measuring the resistivity in the open well at various depth points; determining the difference between the previously determined normal resistivity and the measured resistivity at said various depth points to obtain the actual reduction in normal resistivity; and using the actual reduction in the normal resistivity and nomogram to obtain the distance between the open and cased wells.
Claim 3
Dependent Claim
29 words
The method of claim 1 wherein the normal resistivity and reduction in resistivity are made using resistivity measurements made in the cased well prior to installation of casing therein.
Claim 4
Dependent Claim
25 words
The method of claim 1 wherein a series of nomographs are prepared using various inclinations of the open well with respect to the cased well.
Claim 5
Dependent Claim
36 words
The method of claim 1 wherein a series of nomographs are prepared with the inclination between the cased and open wells varying between 0* and 15* and the resistivity varying between 1 and 5 ohm meters.
Claim 6
Dependent Claim
44 words
The mEthod of claim 1 wherein the resitivity measurements are made using relatively long electrode spacings when the wells are more than 20 feet apart and the resistivity measurements are made using shorter electrode spacings when the wells are less than 20 feet apart.
Claim 7
Dependent Claim
15 words
The method of claim 1 wherein the nomographs are prepared using various assumed casing sizes.
Claim 8
Dependent Claim
21 words
The method of claim 1 wherein the nomographs are prepared using various assumed closest points between the cased and open wells.
Claim 9
Dependent Claim
29 words
The method of claim 1 wherein the nomographs are prepared using a combination of assumed casing size, near point, formation resistivity and inclination between the cased and open wells.
References Cited (Backward Citations)
US3488574A
Cited
US3697864A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-07-23 | 1977-01-22 | 1977-07-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-23 | 1981-01-22 | 1981-07-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-23 | 1985-01-22 | 1985-07-24 | $7700.00 | Window Closed / Lapsed |