US3774033A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Dual spaced epithermal neutron detector porosity logging
Assignee: Texaco Inc
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Filing: 1972-05-17
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Granted: 1973-11-20
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Expires: 1992-05-17
Abstract
Abstract An illustrative embodiment of the invention includes method and apparatus for making earth formation porosity measurements in open or cased well boreholes. A high intensity (1.69 X 109 neutrons/sec.) californium 252 neutron source is used to irradiate earth formations surrounding a well borehole with high energy neutrons. As the high energy neutrons interact with the materials comprising the earth formation their energy is reduced and some having epithermal energy are deflected back into the borehole at spaced distances from the neutron source. Two epithermal energy neutron detectors spaced at different vertical distances from the neutron source and from each other are used to measure the epithermal neutron population at the different distances. The ratio of the counting rates in the two detectors may be interpreted in terms of earth formation porosity by means of a predetermined relationship.
Inventors
- 👤 H Scott
- 👤 M Smith
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 12:40
CPC Classifications
G; G01; G01V; G01V5/00; G01V5/04; G01V5/08; G01V5/10; G01V5/107; G01V5/108
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
118 words
A method for measuring the porosity of earth formations in the vicinity of a well borehole comprising the steps of: irradiating the earth formations in the vicinity of the borehole with fast neutrons from a relatively high intensity neutron source; detecting essentially only the epithermal neutron population at a first spaced distance from said source in the borehole; detecting essentially only the epithermal neutron population at a second different spaced distance from said source in the borehole; discriminating against the detection of the thermal neutron population at said two spaced distances from said source in the borehole; and combining the epithermal neutron population measurements made at said two different spaced distances to derive an indication of formation porosity.
Claim 2
Independent Claim
118 words
A method for measuring the porosity of earth formations in the vicinity of a well borehole comprising the steps of: irradiating the earth formations in the vicinity of the borehole with fast neutrons from a relatively high intensity neutron source; detecting essentially only the epithermal neutron population at a first spaced distance from said source in the borehole; detecting essentially only the epithermal neutron population at a second different spaced distance from said source in the borehole; discriminating against the detection of the thermal neutron population at said two spaced distances from said source in the borehole; and combining the epithermal neutron population measurements made at said two different spaced distances to derive an indication of formation porosity.
Claim 3
Dependent Claim
34 words
The method of claim 1 wherein the step of combining said epithermal neutron population measurements includes taking a ratio of said measurements to provide an indication of the hydrogen index of said earth formations.
Claim 4
Dependent Claim
38 words
The method of claim 1 wherein the irradiating step is performed by irradiating the earth formations in the vicinity of the well borehole with a neutron source comprising a californium 252 source emitting approximately 1.69 X 109 neutrons/sec.
Claim 5
Dependent Claim
42 words
The method of claim 3 wherein the two epithermal neutron detecting steps are performed at spaced distances of about 19 and 31 inches from said californium 252 neutron source by employing cadmium wrapped He3 detectors having effective sensitive centers at these distances.
Claim 6
Dependent Claim
115 words
Apparatus for measuring a porosity related characteristic of earth formations in the vicinity of a well borehole comprising: a fluid tight body member sized for passage in a borehole and housing; a relatively high intensity source of fast neutrons; a first epithermal neutron detector spaced a first longitudinal distance from said neutron source; a second epithermal neutron detector spaced a second different longitudinal distance from said neutron source; shielding means for discriminating against the detection of thermal neutrons at said two different spaced epithermal neutron detectors; and means responsive to signals from said epithermal neutron detectors to generate a signal related to a porosity characteristic of the earth formations in the vicinity of the borehole.
Claim 7
Dependent Claim
115 words
Apparatus for measuring a porosity related characteristic of earth formations in the vicinity of a well borehole comprising: a fluid tight body member sized for passage in a borehole and housing; a relatively high intensity source of fast neutrons; a first epithermal neutron detector spaced a first longitudinal distance from said neutron source; a second epithermal neutron detector spaced a second different longitudinal distance from said neutron source; shielding means for discriminating against the detection of thermal neutrons at said two different spaced epithermal neutron detectors; and means responsive to signals from said epithermal neutron detectors to generate a signal related to a porosity characteristic of the earth formations in the vicinity of the borehole.
Claim 8
Dependent Claim
22 words
The apparatus of claim 5 wherein said neutron source comprises a californium 252 source capable of emitting approximately 1.69 X 109 neutrons/sec.
Claim 9
Dependent Claim
52 words
The apparatus of claim 6 wherein said first epithermal neutron detector is spaced with its effective sensitive center 19 inches from the effective center of said neutron source and said second epithermal neutron detector is spaced with its effective sensitive center approximately 31 inches from the effective center of said neutron source.
Claim 10
Dependent Claim
30 words
The apparatus of claim 7 wherein said epithermal neutron detectors comprise He3 neutron detectors embedded in a neutron moderating material and the whole surrounded by a thermal neutron absorbing material.
Claim 11
Dependent Claim
29 words
The apparatus of claim 8 wherein said He3 neutron detectors are embedded in lucite plastic material and the whole is surrounded by a cadmium shield approximately 0.020 inches thick.
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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) | 1976-11-19 | 1977-05-21 | 1977-11-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-11-19 | 1981-05-21 | 1981-11-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-11-19 | 1985-05-21 | 1985-11-20 | $7700.00 | Window Closed / Lapsed |