US3767921A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Well logging system with linearity control
Assignee: Texaco Inc
•
Filing: 1972-03-31
•
Granted: 1973-10-23
•
Expires: 1992-03-31
Abstract
Abstract An illustrative embodiment of the present invention includes method and apparatus for gamma ray spectroscopy well logging systems including a closed loop linearity control feature. A borehole tool provides gamma ray pulse data. The gamma ray counts in at least two portions of the gamma ray energy spectrum chosen so that their ratio remains relatively constant under usual borehole conditions are monitored. An error signal is developed if the ratio of gamma ray counts in the monitored portions of the energy spectrum deviate significantly from the constant ratio. The error signal is used to control the power supply voltage for the borehole tool and/or the surface amplification of the gamma ray pulse signals to preserve system linearity.
Inventors
- 👤 J Jones
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 11:51
CPC Classifications
G; G01; G01T; G01T1/00; G01T1/36; G01T1/40; G01V; G01V5/00; G01V5/04; G01V5/08; G01V5/10; G01V5/101
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
128 words
A method for linearizing and controlling the gain of a nuclear well logging system comprising the steps of: measuring the energy spectrum of gamma rays produced by earth formation materials surrounding a well borehole; measuring, in at least two predetermined energy band portions of said gamma ray energy spectrum, the number of counts of gamma rays having an energy falling within said energy band portions; generating a signal proportional to the ratio of counts within said at least two predetermined energy band portions and comparing said ratio signal with at least one constant ratio calibration signal; generating an error signal proportional to the difference of said ratio signal and said constant ratio calibration signal; and using said error signal to control the linearity of said well logging system.
Claim 2
Independent Claim
128 words
A method for linearizing and controlling the gain of a nuclear well logging system comprising the steps of: measuring the energy spectrum of gamma rays produced by earth formation materials surrounding a well borehole; measuring, in at least two predetermined energy band portions of said gamma ray energy spectrum, the number of counts of gamma rays having an energy falling within said energy band portions; generating a signal proportional to the ratio of counts within said at least two predetermined energy band portions and comparing said ratio signal with at least one constant ratio calibration signal; generating an error signal proportional to the difference of said ratio signal and said constant ratio calibration signal; and using said error signal to control the linearity of said well logging system.
Claim 3
Dependent Claim
33 words
The method of claim 1 wherein at least three predetermined energy band portions are used and at least two such ratio signals generated and compared with at least two constant ratio calibration signals.
Claim 4
Dependent Claim
31 words
The method of claim 1 wherein two predetermined gamma ray energy band portions each about 0.5 MEV in width and located with centers at about 7.0 and 7.75 MEV are used.
Claim 5
Dependent Claim
75 words
The method of claim 1 wherein two gamma ray energy Band portions situated so that one energy band portion is located approximately near the peak of a known common well borehole material gamma ray line in the gamma ray energy spectrum and a second energy band portion is located approximately on the sloping edge of said known common material gamma ray line in the gamma ray energy spectrum are used to generate said ratio signal.
Claim 6
Dependent Claim
34 words
The method of claim 1 wherein said error signal is used to control the operating voltage supplied to the downhole tool portion of the nuclear well logging system to preserve linearity of the system.
Claim 7
Dependent Claim
132 words
Apparatus for linearizing and controlling the gain of a nuclear well logging system comprising: means for measuring the energy spectrum of gamma rays produced by earth formation materials surrounding a well borehole; means for measuring in at least two predetermined energy band portions of said gamma ray energy spectrum, the number of counts of gamma rays having an energy falling within said energy band portions; means for generating a signal proportional to the ratio of counts within said predetermined energy band portions and for comparing said ratio signal with at least one constant ratio calibration signal; means for generating an error signal proportional to the difference of said ratio signal and said constant ratio calibration signal; and means for using said error signal to control the linearity of said well logging system.
Claim 8
Dependent Claim
132 words
Apparatus for linearizing and controlling the gain of a nuclear well logging system comprising: means for measuring the energy spectrum of gamma rays produced by earth formation materials surrounding a well borehole; means for measuring in at least two predetermined energy band portions of said gamma ray energy spectrum, the number of counts of gamma rays having an energy falling within said energy band portions; means for generating a signal proportional to the ratio of counts within said predetermined energy band portions and for comparing said ratio signal with at least one constant ratio calibration signal; means for generating an error signal proportional to the difference of said ratio signal and said constant ratio calibration signal; and means for using said error signal to control the linearity of said well logging system.
Claim 9
Dependent Claim
44 words
The apparatus of claim 6 wherein said means for using said error signal to control the linearity of said well logging system includes means for controlling the gain of amplification of signals representative of gamma rays from the earth formations surrounding the well borehole.
Claim 10
Dependent Claim
37 words
The apparatus of claim 6 wherein said means for using said error signal to control the linearity of said well logging system includes means for controlling the operating voltage supplied to the downhole portion of said system.
Claim 11
Dependent Claim
32 words
The apparatus of claim 6 wherein said two predetermined gamma ray energy band portions are each about 0.5 MEV in width and are located with centers at about 7.0 and 7.75 MEV.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-10-22 | 1977-04-23 | 1977-10-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-22 | 1981-04-23 | 1981-10-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-22 | 1985-04-23 | 1985-10-23 | $7700.00 | Window Closed / Lapsed |