US3842264A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Radiological well logging methods and apparatus for reducing the effect of activation from the detector crystal
Assignee: Texaco Inc
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Filing: 1972-09-25
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Granted: 1974-10-15
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Expires: 1992-09-25
Abstract
Abstract Improved radioactivity well logging methods and apparatus are provided for determining the macroscopic thermal neutron capture cross section of subsurface earth materials, wherein a correction is made to reduce or eliminate the effects of the portion of the measurement which is due to radiation produced by reactions of the residual fast neutron flux of the accelerator and the activation of the crystal in the detector. The high energy neutron source is pulsed at a preselected rate, during the first portion of the operating cycle, and the resulting capture-induced radiation is measured within the first portion of the operating cycle during two preselected time intervals following the termination of each neutron burst. Thereafter, the source is inactivated during the balance of the operating cycle, and a mesurement is made of the radiations registering in the activated crystal. This latter measurement is then utilized to correct the measurements obtained during the first portion of the operating cycle to a predetermined relationship.
Inventors
- 👤 D Arnold
- 👤 R Pitts
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 05:03
CPC Classifications
G; G01; G01V; G01V5/00; G01V5/04; G01V5/08; G01V5/10; G01V5/101; G01V5/102
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
226 words
A method of radioactivity well logging to investigate subsurface earth formations traversed by a borehole, comprising passing a logging instrument through said borehole, bombarding said formations with a plurality of discrete bursts of high energy neutrons emitted from said instrument during a preselected irradiation time interval occurring during a first portion of the operating cycle to produce a succession of discrete thermal neutron populations in said borehole and formations, detecting radiation at said instrument resulting from capture of said thermal neutron populations during preselected portions of said first portion of the operating cycle, after termination of the first portion of the operating cycle including said irradiation interval and after said thermal neutron populations in said formations have declined to negligible portions, detecting during a preselected subsequent detection time interval other radiations, produced primarily within a component of said logging instrument as a result of said high energy neutrons are emitted from unstable isotopes comprising material of the logging instrument, deriving a first electrical indication generally related to the occurrence of said resulting radiations detected during said first portion of the operating cycle, deriving a second electrical indication generally related to the occurrence of said radiations detected during said subsequent detection interval, and deriving from said first and second electrical indications a corrected representation of a characteristic of the earth material bombarded by said high energy neutrons.
Claim 2
Independent Claim
226 words
A method of radioactivity well logging to investigate subsurface earth formations traversed by a borehole, comprising passing a logging instrument through said borehole, bombarding said formations with a plurality of discrete bursts of high energy neutrons emitted from said instrument during a preselected irradiation time interval occurring during a first portion of the operating cycle to produce a succession of discrete thermal neutron populations in said borehole and formations, detecting radiation at said instrument resulting from capture of said thermal neutron populations during preselected portions of said first portion of the operating cycle, after termination of the first portion of the operating cycle including said irradiation interval and after said thermal neutron populations in said formations have declined to negligible portions, detecting during a preselected subsequent detection time interval other radiations, produced primarily within a component of said logging instrument as a result of said high energy neutrons are emitted from unstable isotopes comprising material of the logging instrument, deriving a first electrical indication generally related to the occurrence of said resulting radiations detected during said first portion of the operating cycle, deriving a second electrical indication generally related to the occurrence of said radiations detected during said subsequent detection interval, and deriving from said first and second electrical indications a corrected representation of a characteristic of the earth material bombarded by said high energy neutrons.
Claim 3
Independent Claim
241 words
A method of radioactivity well logging to investigate subsurface earth formations traversed by a borehole, comprising passing a logging instrument through said borehole, bombarding said formations with a plurality of discrete bursts of high energy neutrons emitted from said instrument during a preselected irradiation time interval occurring during a first portion of the operating cycle to produce a succession of discrete thermal neutron populations in said borehole and formations, detecting radiation at said instrument resulting from capture of said thermal neutron populations during preselected portions of said first portion of the operating cycle, after termination of the first portion of the operating cycle including said irradiation interval and after said thermal neutron populations in said formations have declined to negligible porportions, detecting during a preselected subsequent detection time interval other radiations resulting primarily within a component of said logging instrument as a result of said high energy neutrons which comprises radiation resulting from reactions of residual beam neutrons produced by the neutron source with material comprising at least one component of the logging instrument, deriving a first electrical indication generally related to the occurrence of said resulting radiations detected during said first portion of the operating cycle deriving a second electrical indication generally related to the occurrence of said radiations detected during said subsequent detection interval, and deriving from said first and second electrical indications a corrected representation of a characteristic of the earth material bombarded by said high energy neutrons.
Claim 4
Independent Claim
241 words
A method of radioactivity well logging to investigate subsurface earth formations traversed by a borehole, comprising passing a logging instrument through said borehole, bombarding said formations with a plurality of discrete bursts of high energy neutrons emitted from said instrument during a preselected irradiation time interval occurring during a first portion of the operating cycle to produce a succession of discrete thermal neutron populations in said borehole and formations, detecting radiation at said instrument resulting from capture of said thermal neutron populations during preselected portions of said first portion of the operating cycle, after termination of the first portion of the operating cycle including said irradiation interval and after said thermal neutron populations in said formations have declined to negligible porportions, detecting during a preselected subsequent detection time interval other radiations resulting primarily within a component of said logging instrument as a result of said high energy neutrons which comprises radiation resulting from reactions of residual beam neutrons produced by the neutron source with material comprising at least one component of the logging instrument, deriving a first electrical indication generally related to the occurrence of said resulting radiations detected during said first portion of the operating cycle deriving a second electrical indication generally related to the occurrence of said radiations detected during said subsequent detection interval, and deriving from said first and second electrical indications a corrected representation of a characteristic of the earth material bombarded by said high energy neutrons.
Claim 5
Independent Claim
250 words
A method of radioactivity well logging to investigate subsurface earth formations traversed by a borehole, comprising: passing a logging instrument through said borehole, bombarding said formations with a discrete burst of high energy neutrons emitted from said instrument during a first portion of the operating cycle including a preselected irradiation time interval to produce a discrete thermal neutron population in said borehole and formations, during said first portion of the operating cycle detecting radiation at said instrument resulting from capture of at least said thermal neutron populations in said formations during preselected time intervals following said burst of high energy neutrons, after termination of said first portion of the operating cycle including said irradiation interval and after said thermal neutron populations have declined to negligible proportions, detecting during a preselected detection time interval other radiations produced primarily within a component of said logging instrument as a result of said high energy neutrons which comprises radiation resulting from reactions of residual beam neutrons from the source with material comprising at least one component of the logging instrument, deriving a first electrical indication generally related to the occurrence of said resulting radiations detecting during said first portion of said operating cycle, and deriving a second electrical indication generally related to the occurrence of said resulting radiations detected during the second portion of said operating cycle, and deriving from said first and second electrical indications a corrected representation of a characteristic of the material of the formations bombarded by said high energy neutrons.
Claim 6
Independent Claim
250 words
A method of radioactivity well logging to investigate subsurface earth formations traversed by a borehole, comprising: passing a logging instrument through said borehole, bombarding said formations with a discrete burst of high energy neutrons emitted from said instrument during a first portion of the operating cycle including a preselected irradiation time interval to produce a discrete thermal neutron population in said borehole and formations, during said first portion of the operating cycle detecting radiation at said instrument resulting from capture of at least said thermal neutron populations in said formations during preselected time intervals following said burst of high energy neutrons, after termination of said first portion of the operating cycle including said irradiation interval and after said thermal neutron populations have declined to negligible proportions, detecting during a preselected detection time interval other radiations produced primarily within a component of said logging instrument as a result of said high energy neutrons which comprises radiation resulting from reactions of residual beam neutrons from the source with material comprising at least one component of the logging instrument, deriving a first electrical indication generally related to the occurrence of said resulting radiations detecting during said first portion of said operating cycle, and deriving a second electrical indication generally related to the occurrence of said resulting radiations detected during the second portion of said operating cycle, and deriving from said first and second electrical indications a corrected representation of a characteristic of the material of the formations bombarded by said high energy neutrons.
Claim 7
Independent Claim
243 words
A method of radioactivity well logging to investigate subsurface earth formations traversed by a borehole, comprising: passing a logging instrument through said borehole, bombarding said formations with a discrete burst of high energy neutrons emitted from said instrument during a first portion of the operating cycle including a preselected irradiation time interval to produce a discrete thermal neutron population in said borehole and formations, during said first portion of the operating cycle detecting radiation at said instrument resulting from capture of at least said thermal neutron populations in said formations during preselected time intervals following said burst of high energy neutrons, after termination of said first portion of the operating cycle including said irradiation interval and after said thermal neutron populations have declined to negligible proportions, detecting during a preselected detection time interval other radiations produced primarily within a component of said logging instrument as a result of said high energy neutrons, which comprises radiation resulting from activation of material comprising at least one component of the logging instrument, deriving a first electrical indication generally related to the occurrence of said resulting radiations detected during said first portion of said operating cycle, and deriving a second electrical indication generally related to the occurrence of said resulting radiations detected during the second portion of said operating cycle, and deriving from said first and second electrical indications a corrected representation of a characteristic of the material of the formations bombarded by said high energy neutrons.
Claim 8
Independent Claim
243 words
A method of radioactivity well logging to investigate subsurface earth formations traversed by a borehole, comprising: passing a logging instrument through said borehole, bombarding said formations with a discrete burst of high energy neutrons emitted from said instrument during a first portion of the operating cycle including a preselected irradiation time interval to produce a discrete thermal neutron population in said borehole and formations, during said first portion of the operating cycle detecting radiation at said instrument resulting from capture of at least said thermal neutron populations in said formations during preselected time intervals following said burst of high energy neutrons, after termination of said first portion of the operating cycle including said irradiation interval and after said thermal neutron populations have declined to negligible proportions, detecting during a preselected detection time interval other radiations produced primarily within a component of said logging instrument as a result of said high energy neutrons, which comprises radiation resulting from activation of material comprising at least one component of the logging instrument, deriving a first electrical indication generally related to the occurrence of said resulting radiations detected during said first portion of said operating cycle, and deriving a second electrical indication generally related to the occurrence of said resulting radiations detected during the second portion of said operating cycle, and deriving from said first and second electrical indications a corrected representation of a characteristic of the material of the formations bombarded by said high energy neutrons.
Claim 9
Independent Claim
247 words
A method of radioactivity well logging to investigate subsurface earth formations traversed by a borehole, comprising: passing a logging instrument through said borehole, bombarding said formations with a discrete burst of high energy neutrons emitted from said instrument during a first portion of the operating cycle including a preselected irradiation time interval to produce a discrete thermal neutron population in said borehole and formations, during said first portion of the operatinG cycle detecting radiation at said instrument resulting from capture of at least said thermal neutron populations in said formations during preselected time intervals following said burst of high energy neutrons, after termination of said first portion of the operating cycle including said irradiation interval and after said thermal neutron populations have declined to negligible proportions, detecting during a preselected detection time interval other radiations resulting from unstable isotopes produced primarily within a component of said logging instrument comprising material of the radiation detector and from reactions of residual beam neutrons from the source with at least one component of the logging instrument, deriving a first electrical indication generally related to the occurrence of said resulting radiations detected during said first portion of said operating cycle, and deriving a second electrical indication generally related to the occurrence of said resulting radiations detected during the second portion of said operating cycle, and deriving from said first and second electrical indications a corrected representation of a characteristic of the material of the formations bombarded by said high energy neutrons.
Claim 10
Independent Claim
247 words
A method of radioactivity well logging to investigate subsurface earth formations traversed by a borehole, comprising: passing a logging instrument through said borehole, bombarding said formations with a discrete burst of high energy neutrons emitted from said instrument during a first portion of the operating cycle including a preselected irradiation time interval to produce a discrete thermal neutron population in said borehole and formations, during said first portion of the operatinG cycle detecting radiation at said instrument resulting from capture of at least said thermal neutron populations in said formations during preselected time intervals following said burst of high energy neutrons, after termination of said first portion of the operating cycle including said irradiation interval and after said thermal neutron populations have declined to negligible proportions, detecting during a preselected detection time interval other radiations resulting from unstable isotopes produced primarily within a component of said logging instrument comprising material of the radiation detector and from reactions of residual beam neutrons from the source with at least one component of the logging instrument, deriving a first electrical indication generally related to the occurrence of said resulting radiations detected during said first portion of said operating cycle, and deriving a second electrical indication generally related to the occurrence of said resulting radiations detected during the second portion of said operating cycle, and deriving from said first and second electrical indications a corrected representation of a characteristic of the material of the formations bombarded by said high energy neutrons.
Claim 11
Dependent Claim
39 words
The method of claim 5 wherein further radiations resulting from reactions of residual beam neutrons with various elements within said earth formations are also detected along with said other radiations produced primarily within a component of said logging instrument.
Claim 12
Dependent Claim
260 words
A radioactivity well logging system comprising a subsurface logging instrument adapted to be passed through a borehole, a source of high energy neutrons arranged in said instrument for irradiating subsurface earth materials surrounding said borehole, wherein said source also produces residual beam neutrons which interact with material comprising at least one component of the logging instrument to produce radiation in said material of said logging instrument, a detector arranged in said instrument for detecting radiation from each formations adjacent the borehole as a result of irradiation thereof by neutrons from said source, said detector comprising as a component thereof material susceptible of being activated into an unstable radioisotope due to radiation emitted by said source, whereby radiation is emitted from said activated material of the detector, pulsing means for intermittently actuating said source to produce said neutrons in discrete bursts during a first portion of an operating cycle including a predetermined irradiation time interval, and means including said detector for selectively detecting radiation resulting from said irradiation of said earth formations at preselected time intervals during said first portion of said operating cycle and for selectively detecting radiation resulting primarily from activation of component material of said detector during a predetermined detection time interval occurring after substantial decay of said irradiating bursts of neutrons in said earth material and following the termination of said first portion of said operating cycle including said irradiation time interval, said selective detecting means includes means for detecting said radiation produced in a component of said logging instrument as a result of said beam current.
Claim 13
Dependent Claim
260 words
A radioactivity well logging system comprising a subsurface logging instrument adapted to be passed through a borehole, a source of high energy neutrons arranged in said instrument for irradiating subsurface earth materials surrounding said borehole, wherein said source also produces residual beam neutrons which interact with material comprising at least one component of the logging instrument to produce radiation in said material of said logging instrument, a detector arranged in said instrument for detecting radiation from each formations adjacent the borehole as a result of irradiation thereof by neutrons from said source, said detector comprising as a component thereof material susceptible of being activated into an unstable radioisotope due to radiation emitted by said source, whereby radiation is emitted from said activated material of the detector, pulsing means for intermittently actuating said source to produce said neutrons in discrete bursts during a first portion of an operating cycle including a predetermined irradiation time interval, and means including said detector for selectively detecting radiation resulting from said irradiation of said earth formations at preselected time intervals during said first portion of said operating cycle and for selectively detecting radiation resulting primarily from activation of component material of said detector during a predetermined detection time interval occurring after substantial decay of said irradiating bursts of neutrons in said earth material and following the termination of said first portion of said operating cycle including said irradiation time interval, said selective detecting means includes means for detecting said radiation produced in a component of said logging instrument as a result of said beam current.
References Cited (Backward Citations)
US3733486A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-10-14 | 1978-04-15 | 1978-10-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-10-14 | 1982-04-15 | 1982-10-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-10-14 | 1986-04-15 | 1986-10-15 | $7700.00 | Window Closed / Lapsed |