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US3886355A
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Method and apparatus for logging well boreholes with gamma rays from the inelastic scattering of fast neutrons
Assignee: Western Atlas International Inc
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Filing: 1972-10-03
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Granted: 1975-05-27
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Expires: 1992-10-03
Abstract
Abstract A fast neutron source is periodically switched between a pulsed mode and a continuous mode. A first gamma ray detection interval follows the pulsed mode to provide an indication of the capture gamma rays. A second detection interval occurs during the continuous mode to provide an indication of the capture gamma rays plus the gamma rays resulting from the inelastic scattering of fast neutrons. The first indication is subtracted from the second, resulting in an indication solely of the gamma rays from inelastic scattering. The pulses occurring in such intervals are further subjected to energy discrimination which provides information relating to carbon and oxygen content, such information being used with a ratio circuit to provide a carbon/oxygen ratio. In another embodiment, a pair of neutron sources, one pulsed, one continuous, provide analogous results. In still another embodiment, the borehole is first logged with a pulsed source and then later with a continuous source. In yet another embodiment, a shielding, rotating disk having alternate short and long windows is used between an alpha particle source and a neutron emitter to simulate the pulsed and continuous modes. An electrical signal functionally related to the lithology of the formations, for example, the silicon/calcium ratio of the formations, is used in conjunction with an electrical signal indicative of the carbon/oxygen ratio to generate an electrical signal indicative of the hydrocarbon saturation of the formations.
Inventors
- 👤 Richard B Culver
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 14:07
CPC Classifications
G; G01; G01V; G01V5/00; G01V5/04; G01V5/08; G01V5/10; G01V5/101; G01V5/102
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
157 words
A method of well logging comprising the steps of: irradiating the formations surrounding an earth borehole with high energy neutrons; detecting radiations emanating from said formations resulting from said formations being irradiated by said neutrons; generating a first electrical signal based upon said detected radiations relating to the carbon content of said formations; generating a second electrical signal based upon said detected radiations relating to the oxygen content of said formations; generating a third electrical signal based upon said detected radiations relating to the silicon content of said formations; generating a fourth electrical signal based upon said detected radiations relating to the calcium content of said formations; generating a fifth electrical signal functionally related to the ratio of said first and second signals; generating a sixth electrical signal functionally related to the ratio of said third and fourth electrical signals; and modifying said fifth electrical signal as a function of a characteristic of said sixth electrical signal.
Claim 2
Independent Claim
157 words
A method of well logging comprising the steps of: irradiating the formations surrounding an earth borehole with high energy neutrons; detecting radiations emanating from said formations resulting from said formations being irradiated by said neutrons; generating a first electrical signal based upon said detected radiations relating to the carbon content of said formations; generating a second electrical signal based upon said detected radiations relating to the oxygen content of said formations; generating a third electrical signal based upon said detected radiations relating to the silicon content of said formations; generating a fourth electrical signal based upon said detected radiations relating to the calcium content of said formations; generating a fifth electrical signal functionally related to the ratio of said first and second signals; generating a sixth electrical signal functionally related to the ratio of said third and fourth electrical signals; and modifying said fifth electrical signal as a function of a characteristic of said sixth electrical signal.
Claim 3
Independent Claim
90 words
A method of well logging comprising the steps of: irradiating the formations surrounding an earth borehole with high energy neutrons; detecting radiations emanating from said formations resulting from said formations being irradiated by said neutrons; establishing a first electrical signal based upon said detected radiations functionally related to the carbon/oxygen content of said formations; establishing a second electrical signal based upon said detected radiations functionally related to the silicon/calcium content of said formations; and modifying said first electrical signal as a function of a characteristic of said second electrical signal.
Claim 4
Independent Claim
90 words
A method of well logging comprising the steps of: irradiating the formations surrounding an earth borehole with high energy neutrons; detecting radiations emanating from said formations resulting from said formations being irradiated by said neutrons; establishing a first electrical signal based upon said detected radiations functionally related to the carbon/oxygen content of said formations; establishing a second electrical signal based upon said detected radiations functionally related to the silicon/calcium content of said formations; and modifying said first electrical signal as a function of a characteristic of said second electrical signal.
Claim 5
Independent Claim
85 words
A system for logging earth boreholes, comprising: means to irradiate the formations surrounding an earth borehole with high energy neutrons; means for detecting radiations emanating from said formations resulting from said formations being irradiated by said neutrons; means for establishing a first electrical signal indicative of the carbon/oxygen content of said formations; means for providing a second electrical signal indicative of the lithology of said formations; and means to modify said first electrical signal as a function of a characteristic of said second electrical signal.
Claim 6
Independent Claim
85 words
A system for logging earth boreholes, comprising: means to irradiate the formations surrounding an earth borehole with high energy neutrons; means for detecting radiations emanating from said formations resulting from said formations being irradiated by said neutrons; means for establishing a first electrical signal indicative of the carbon/oxygen content of said formations; means for providing a second electrical signal indicative of the lithology of said formations; and means to modify said first electrical signal as a function of a characteristic of said second electrical signal.
Claim 7
Independent Claim
85 words
A system for logging earth boreholes, comprising: means to irradiate the formations surrounding an earth borehole with high energy neutrons; means for detecting radiations emanating from said formations resulting from said formations being irradiated by said neutrons; means for establishing a first electrical signal indicative of the carbon/oxygen content of said formations; means for providing a second electrical signal indicative of the porosity of said formations; and means to modify said first electrical signal as a function of a characteristic of said second electrical signal.
Claim 8
Independent Claim
85 words
A system for logging earth boreholes, comprising: means to irradiate the formations surrounding an earth borehole with high energy neutrons; means for detecting radiations emanating from said formations resulting from said formations being irradiated by said neutrons; means for establishing a first electrical signal indicative of the carbon/oxygen content of said formations; means for providing a second electrical signal indicative of the porosity of said formations; and means to modify said first electrical signal as a function of a characteristic of said second electrical signal.
References Cited (Backward Citations)
US3483376A
Cited
US3780301A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-05-26 | 1978-11-25 | 1979-05-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-05-26 | 1982-11-25 | 1983-05-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-05-26 | 1986-11-25 | 1987-05-27 | $7700.00 | Window Closed / Lapsed |