US3567935A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Measuring apparatus and method
Assignee: Schlumberger Technology Corp
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Filing: 1968-02-07
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Granted: 1971-03-02
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Expires: 1988-02-07
Abstract
Abstract An earth formation porosity logging tool in accordance with an illustrative embodiment of the invention comprises a neutron source and four neutron detectors spaced at different distances from the source for transport through a borehole. Signals are obtained that correspond to the ratios of the counts registered by the two short-spaced detectors and the two long-spaced detectors. The effect of the borehole on the formation porosity measurement is compensated by combining these ration signals to eliminate the influence of the borehole neutron relaxation length and converting the resultant signal into an output signal that more accurately indicates the formation porosity.
Inventors
- 👤 Walter A Nagel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 04:35
CPC Classifications
G; G01; G01V; G01V5/00; G01V5/04; G01V5/08; G01V5/10; G01V5/107
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
159 words
A borehole tool for logging earth formations comprising a housing, a neutron source within the housing for establishing a neutron distribution within the borehole and the earth formations, four neutron detectors each spaced at a different respective distances from said neutron source and responsive to the same neutron phenomena to produce signals that correspond to said neutron distribution in the borehole and the earth formations, and circuit means responsive to said detector signals for producing further signals that are related to the ratios of the neutron populations observed by said two detectors closest to said neutron source, Rnear, and said two detectors spaced most distant from said neutron source, Rfar, according to the equation: Lformation (1- Alpha Beta ) f(Rfar) - Alpha gRnear) where Lformation is the relaxation length of the neutrons in the earth formations; Alpha and Beta are weighting factors that characterize the tool configuration; and f and g are functions that also characterize the tool configuration.
Claim 2
Dependent Claim
159 words
A borehole tool for logging earth formations comprising a housing, a neutron source within the housing for establishing a neutron distribution within the borehole and the earth formations, four neutron detectors each spaced at a different respective distances from said neutron source and responsive to the same neutron phenomena to produce signals that correspond to said neutron distribution in the borehole and the earth formations, and circuit means responsive to said detector signals for producing further signals that are related to the ratios of the neutron populations observed by said two detectors closest to said neutron source, Rnear, and said two detectors spaced most distant from said neutron source, Rfar, according to the equation: Lformation (1- Alpha Beta ) f(Rfar) - Alpha gRnear) where Lformation is the relaxation length of the neutrons in the earth formations; Alpha and Beta are weighting factors that characterize the tool configuration; and f and g are functions that also characterize the tool configuration.
Claim 3
Dependent Claim
20 words
A logging tool according to claim 1 wherein said neutron source is separated from said detectors by a neutron moderator.
Claim 4
Dependent Claim
20 words
A logging tool according to claim 1 wherein said neutron source comprises an activity on the order of 20 curies.
Claim 5
Dependent Claim
213 words
A borehole tool for logging earth formations comprising a housing, a neutron source within said housing for establishing a neutron distribution within the borehole and the earth formations, three neutron detectors each spaced from said source at a different respective distance and responsive to the same neutron phenomena to produce signals that correspond to the relaxation length of neutrons in the earth formation and the borehole, circuit means responsive to said neutron detectors spaced most closely to and intermediate of the distance from said neutron source for producing a signal that corresponds to the ratio, Rnear, of said neutron distribution registered by said detectors, further circuit means responsive to said intermediate and said most distantly spaced neutron detectors for producing a signal that corresponds to the ratio, Rfar , of said neutron distribution registered by said detectors, and circuit means coupled to said ratio signals for producing an output signal that corresponds to the relaxation length of neutrons in the earth formation substantially according to the equation: Lformation (1- Alpha Beta ) f(Rfar) - Alpha g Rnear ) where Lformation is the relaxation length of the neutrons in the earth formation; Alpha and Beta are weighting factors that characterize tool configuration; and f and g are functions that also characterize the tool configuration.
Claim 6
Dependent Claim
213 words
A borehole tool for logging earth formations comprising a housing, a neutron source within said housing for establishing a neutron distribution within the borehole and the earth formations, three neutron detectors each spaced from said source at a different respective distance and responsive to the same neutron phenomena to produce signals that correspond to the relaxation length of neutrons in the earth formation and the borehole, circuit means responsive to said neutron detectors spaced most closely to and intermediate of the distance from said neutron source for producing a signal that corresponds to the ratio, Rnear, of said neutron distribution registered by said detectors, further circuit means responsive to said intermediate and said most distantly spaced neutron detectors for producing a signal that corresponds to the ratio, Rfar , of said neutron distribution registered by said detectors, and circuit means coupled to said ratio signals for producing an output signal that corresponds to the relaxation length of neutrons in the earth formation substantially according to the equation: Lformation (1- Alpha Beta ) f(Rfar) - Alpha g Rnear ) where Lformation is the relaxation length of the neutrons in the earth formation; Alpha and Beta are weighting factors that characterize tool configuration; and f and g are functions that also characterize the tool configuration.
Claim 7
Dependent Claim
20 words
A logging tool according to claim 4 wherein said neutron source is separated from said detectors by a neutron moderator.
Claim 8
Dependent Claim
20 words
A logging tool according to claim 4 wherein said neutron source comprises an activity on the order of 20 curies.
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) | 1974-03-01 | 1974-08-31 | 1975-03-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-03-01 | 1978-08-31 | 1979-03-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-03-01 | 1982-08-31 | 1983-03-02 | $7700.00 | Window Closed / Lapsed |