US4862424A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Interferometric means and method for accurate determination of fiberoptic well logging cable length
Assignee: Chevron USA Inc
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Filing: 1988-03-15
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Granted: 1989-08-29
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Expires: 2008-03-15
Abstract
Abstract A method and means for determining the amount of stretch in a well logging cable is disclosed. An optical fiber is run into a well with a logging cable and looped back to the surface. A second optical fiber of nominal length is maintained on the surface. A source of monochromatic light is passed through both fibers and recombined. As the well logging tool is raised and lowered in the wellbore, the number of interference fringes passing a fixed point is determined. The change in length of the optical fiber and, therefore, the cable will be equal to 1/2 the number of interference fringes passing a fixed point times the wavelength of light used. A precise determination of vertical location can then be made when this information is combined with information from a surface mounted odometer or encoder. This information further allows a precise determination of interval bulk density or other formation parameters in which it is important to know the depth of a tool.
Inventors
- 👤 Peter Graebner
- 👤 Swan A. Sie
- 👤 Jorg A. Angehrn
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 02:30
CPC Classifications
E; E21; E21B; E21B47/00; E21B47/04; G; G01; G01B; G01B11/00; G01B11/02; G01B11/04; G01B11/043; G01B11/16; G01B11/161
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
131 words
Apparatus for determining the change in length of a fiber optic well logging cable comprising: a first optical fiber, said first optical fiber adapted to be held in a well logging cable, said fiber subject to a change in length; a second optical fiber of substantially fixed length; a source of monochromatic light operably connected to a first end of said first optical fiber and a first end of said second optical fiber; means for combining a light beam from a second end of said first fiber and the light beam from a second end of said second fiber into a combined beam; and means for detecting changes in an interference fringe pattern in said combined beam, whereby said change in length of said well logging cable can be accurately determined.
Claim 2
Dependent Claim
131 words
Apparatus for determining the change in length of a fiber optic well logging cable comprising: a first optical fiber, said first optical fiber adapted to be held in a well logging cable, said fiber subject to a change in length; a second optical fiber of substantially fixed length; a source of monochromatic light operably connected to a first end of said first optical fiber and a first end of said second optical fiber; means for combining a light beam from a second end of said first fiber and the light beam from a second end of said second fiber into a combined beam; and means for detecting changes in an interference fringe pattern in said combined beam, whereby said change in length of said well logging cable can be accurately determined.
Claim 3
Dependent Claim
19 words
Apparatus as recited in claim 1 wherein said source of monochromatic light is a laser and a beam splitter.
Claim 4
Dependent Claim
20 words
Apparatus as recited in claim 1 further comprising unstretched cable measuring means slidably connected to said cable at said borehole.
Claim 5
Independent Claim
142 words
A method of determining the change in length of an optical fiber in a well logging cable comprising: splitting a single beam of monochromatic light between a first end of a first optical fiber and a first end of a second optical fiber, said second optical fiber fixably attached to a well logging cable, said well logging cable adapted to hold a well logging tool, said second optical fiber subject to a change in length; combining a light beam from a second end of said second optical fiber and a light beam from second end of said first optical fiber to form a combined beam; detecting an interference pattern in said combined beam; determining a number of interference fringes which pass a fixed point; and calculating the change in length of said well logging cable based on said number of interference fringes.
Claim 6
Independent Claim
142 words
A method of determining the change in length of an optical fiber in a well logging cable comprising: splitting a single beam of monochromatic light between a first end of a first optical fiber and a first end of a second optical fiber, said second optical fiber fixably attached to a well logging cable, said well logging cable adapted to hold a well logging tool, said second optical fiber subject to a change in length; combining a light beam from a second end of said second optical fiber and a light beam from second end of said first optical fiber to form a combined beam; detecting an interference pattern in said combined beam; determining a number of interference fringes which pass a fixed point; and calculating the change in length of said well logging cable based on said number of interference fringes.
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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) | 1992-08-28 | 1993-02-27 | 1993-08-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-08-28 | 1997-02-27 | 1997-08-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-08-28 | 2001-02-27 | 2001-08-29 | $7700.00 | Window Closed / Lapsed |