US3890501A
Expired / Lapsed
US
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Neutron logging reliability techniques and apparatus
Assignee: Schlumberger Technology Corp
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Filing: 1973-05-01
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Granted: 1975-06-17
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Expires: 1993-05-01
Abstract
Abstract Apparatus and methods for verifying the validity of data derived at least in part by neutron logging of earth formations, and, where indicated, for affording neutron diffusion-corrected values of such data, are disclosed. In the illustrative embodiments described, an earth formation is irradiated with discrete pulses of high-energy neutrons, and a neutron characteristic of the formation is measured at a first location spaced from the neutron source by observing the neutron population decay at that location during a time period between pulses that is a function of a like earlier measurement of the neutron characteristic. The neutron population decay at a second location in the formation is also measured during a time period that is functionally related to a measured value of the neutron characteristic, conveniently the earlier measured value at the first location. An indication is then derived in response to the population decay measurement at the second location of the validity, specifically, of either the earlier or current value of the neutron characteristic measured at the first location as a measure of the intrinsic value of the neutron characteristic and, generally, of the validity of other neutron-logging derived data as well. Advantageously, the neutron characteristic measured is a thermal neutron absorption characteristic of the formation, such as the thermal decay time constant. In effect, apparent values of the neutron characteristic are observed at both measurement locations and a comparison of these observations made to determine the extent of correlation therebetween. Close agreement of the apparent values indicates an accurate measurement of the intrinsic formation characteristic. Substantial disagreement betweenthe apparent values evidences that perturbational effects have significantly influenced the neutron characteristic measurement and that appropriate correction of the measurement should be made.
Inventors
- 👤 Charles Wilkin Johnstone
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 21:15
CPC Classifications
G; G01; G01V; G01V5/00; G01V5/04; G01V5/08; G01V5/10; G01V5/107; G01V5/108; G01V5/101; G01V5/102
Claims Analysis
Total Claims: 55
Claim 1
Independent Claim
203 words
A method for providing verifiably accurate logging data derived at least in part by neutron logging of earth formation characteristics, comprising the steps of: irradiating an earth formation with discrete pulses of highenergy neutrons to produce therein between pulses a population of neutrons, the decay of which is functionally related to intrinsic neutron characteristics of the formation; detecting indications of the neutron population in the formation between neutron pulses at a first location spaced from the neutron source; deriving a representation of an apparent value of a selected one of said neutron characteristics corresponding to the detected indications at the first location; detecting indications of the neutron population in the formation between neutron pulses at a second location spaced from the first location and from the neutron source; and combining said first location apparent value representation and a function of said second location detected indications to derive a representation functionally related to a quotient of the apparent values of said selected neutron characteristic corresponding to the detected neutron population indications at the first and second locations, thereby to provide information as to the validity of said first location apparent value representation as a measurement of the intrinsic value of said selected neutron characteristic.
Claim 2
Independent Claim
203 words
A method for providing verifiably accurate logging data derived at least in part by neutron logging of earth formation characteristics, comprising the steps of: irradiating an earth formation with discrete pulses of highenergy neutrons to produce therein between pulses a population of neutrons, the decay of which is functionally related to intrinsic neutron characteristics of the formation; detecting indications of the neutron population in the formation between neutron pulses at a first location spaced from the neutron source; deriving a representation of an apparent value of a selected one of said neutron characteristics corresponding to the detected indications at the first location; detecting indications of the neutron population in the formation between neutron pulses at a second location spaced from the first location and from the neutron source; and combining said first location apparent value representation and a function of said second location detected indications to derive a representation functionally related to a quotient of the apparent values of said selected neutron characteristic corresponding to the detected neutron population indications at the first and second locations, thereby to provide information as to the validity of said first location apparent value representation as a measurement of the intrinsic value of said selected neutron characteristic.
Claim 3
Dependent Claim
19 words
The method of claim 1 wherein said selected neutron characteristic is a thermal neutron absorption characteristic of the formation.
Claim 4
Dependent Claim
19 words
The method of claim 1 further comprising the step of recording said quotient-related representation as a function of depth.
Claim 5
Dependent Claim
41 words
The method of claim 1 further comprising the step of combining a function of said first location apparent value representation and a function of said quotient-related representation to provide a corrected representation of the intrinsic value of said selected neutron characteristic.
Claim 6
Dependent Claim
21 words
The method of claim 4 wherein the first location is spaced closer to the neutron source than is the second location.
Claim 7
Dependent Claim
97 words
The method of claim 1 further comprising the steps of: recording said first location apparent value representation of said selected neutron characteristic at least so long as said quotient-related representation is greater than a predetermined reference value; combining a function of said first location apparent value representation and a function of said quotient-related representation at least when said quotient-related representation is less than said reference value to provide a corrected representation of the intrinsic value of said selected neutron characteristic; and recording said corrected representation at least when said quotient-related representation is less than said reference value.
Claim 8
Dependent Claim
44 words
The method of claim 1 wherein said combining step comprises: deriving a representation of an apparent value of said selected neutron characteristic corresponding to the detected indications at said second location; and forming the ratio of said first and second location apparent value representations.
Claim 9
Dependent Claim
103 words
The method of claim 1 wherein: said first location apparent value representation deriving step comprises measuring the neutron population in the formation at said first location in response to first location detected indications occurring during a measurement period following a neutron pulse and deriving said apparent value representation from said neutron population measurement; and said combining step comprises controlling the timing of the measurement period following a subsequent neutron pUlse as a function of said apparent value representation and measuring the neutron population in the formation at said second location in response to second location detected indications occurring during said controlled measurement period.
Claim 10
Dependent Claim
234 words
The method of claim 8 wherein: the step of measuring the neutron population at the first location comprises measuring the neutron population during each of first and second time intervals within the measurement period following said neutron pulse; the step of deriving said apparent value representation corresponding to the neutron population measurement at the first location comprises forming the ratio of the neutron population measurements during the first and second time intervals and determining the timings of the first and second intervals required to maintain the neutron population ratio substantially at a predetermined number, the duration thus determined of at least one of the first and second intervals providing a representation of an apparent value of said selected neutron characteristic; the step of controlling the timing of the measurement period following a subsequent neutron pulse comprises equating the timings of first and second time intervals within said subsequent measurement period to those required to maintain said neutron populations ratio substantially at said predetermined number; the step of measuring the neutron population at the second location comprises measuring the neutron population during each of the first and second intervals of said subsequent measurement period; and the step of deriving a representation functionally related to a quotient of said apparent values comprises forming the ratio of the neutron population measurements at the second location during the first and second time intervals of said subsequent measurement period.
Claim 11
Dependent Claim
37 words
The method of claim 9 further comprising the step of computing a measurement of the intrinsic value of said selected neutron characteristic as a function of said ratio of the neutron population measurements at the second location.
Claim 12
Dependent Claim
58 words
The method of claim 9 further comprising the step of combining a function of said first location apparent value representation and a function of said ratio of the neutron population measurements at the second location to provide a representation of the apparent value of said selected neutron characteristic corresponding to the neutron population measurement at the second location.
Claim 13
Dependent Claim
46 words
The method of claim 9 further comprising the step of correcting said first location apparent value representation by a function of said ratio of the neutron population measurements at the second location to provide a corrected indication of the intrinsic value of said selected neutron characteristic.
Claim 14
Dependent Claim
21 words
The method of claim 12 wherein the first location is spaced closer to the neutron source than is the second location.
Claim 15
Independent Claim
230 words
A method for providing logging data derived at least in part by neutron logging of earth formation characteristics, comprising the steps of: irradiating an earth formation with discrete pulses of high-energy neutrons to produce therein between pulses a population of neutrons, the decay of which is functionally related to intrinsic neutron characteristics of the formation; measuring the neutron population in the formation at a first location spaced from the neutron source during a measurement period between neutron pulses; deriving a representation of an apparent value of a selected one of said neutron characteristics corresponding to the neutron population measurement at the first location; measuring the neutron population in the formation at a second location spaced from the first location and from the neutron source during a measurement period between neutron pulses to produce second location neutron population measurements; combining said first location apparent value representation and a function of said second location neutron population measurements to derive a representaTion related to a function of the apparent values of said selected neutron characteristic corresponding to said neutron population measurements at the first and second locations; and combining said first location apparent value representation and said representation related to a function of the first and second location apparent values to derive a representation of an apparent value of said selected neutron characteristic corresponding to the neutron population measurement at the second location.
Claim 16
Independent Claim
230 words
A method for providing logging data derived at least in part by neutron logging of earth formation characteristics, comprising the steps of: irradiating an earth formation with discrete pulses of high-energy neutrons to produce therein between pulses a population of neutrons, the decay of which is functionally related to intrinsic neutron characteristics of the formation; measuring the neutron population in the formation at a first location spaced from the neutron source during a measurement period between neutron pulses; deriving a representation of an apparent value of a selected one of said neutron characteristics corresponding to the neutron population measurement at the first location; measuring the neutron population in the formation at a second location spaced from the first location and from the neutron source during a measurement period between neutron pulses to produce second location neutron population measurements; combining said first location apparent value representation and a function of said second location neutron population measurements to derive a representaTion related to a function of the apparent values of said selected neutron characteristic corresponding to said neutron population measurements at the first and second locations; and combining said first location apparent value representation and said representation related to a function of the first and second location apparent values to derive a representation of an apparent value of said selected neutron characteristic corresponding to the neutron population measurement at the second location.
Claim 17
Dependent Claim
19 words
The method of claim 14 wherein said selected neutron characteristic is a thermal neutron absorption characteristic of the formation.
Claim 18
Dependent Claim
21 words
The method of claim 14 wherein the first location is spaced closer to the neutron source than is the second location.
Claim 19
Dependent Claim
131 words
The method of claim 14 wherein: the step of deriving said first location apparent value representation comprisese controlling the timing of first and second detection intervals within the measurement period as a function of said apparent value representation; the step of combining said first location apparent value representation and a function of said second location neutron population measurements comprises controlling the measuring of the neutron population at the second location so as to provide a measurement of the neutron population at said second location during each of said first and second detection intervals; and the function of said second location neutron population measurements combined with said first location apparent value representation is a function of the ratio of the first and second detection interval neutron population measurements at the second location.
Claim 20
Dependent Claim
54 words
The method of claim 17 wherein the representation derived by combining said first location apparent value representation and said ratio function of the second location neutron population measurements is related to the ratio of the apparent values of said selected neutron characteristic corresponding to the neutron population measurements at said first and second locations.
Claim 21
Dependent Claim
36 words
The method of claim 18 wherein the step of combining said first location apparent value representation and said apparent values ratio-related function comprises dividing said first location apparent value representation by said apparent values ratio-related function.
Claim 22
Independent Claim
213 words
A method for providing verifiably accurate logging data derived at least in part by neutron logging of earth formation characteristics, comprising the steps of: irradiating an earth formation with discrete pulses of high-energy neutrons, the decay of which is functionally related to intrinsic neutron characteristics of the formation; detecting indications of the neutron population in the formation between neutron pulses at a first location speed from the neutron source; deriving a representation of an apparent value of a selected one of said neutron characteristics corresponding to the detected indications at the first location; detecting indications of the neutron population in the formation between neutron pulses at a second location spaced from the first location and from the neutron source; combining said first location apparent value representation and a function of said second location detected indications to derive a representation functionally related to the quality of said first location apparent value representation as a measurement of the intrinsic value of said selected neutron characteristic; and combining said first location apparent value representation and said quality representation to derive a representation of an apparent value of said selected neutron characteristic corresponding to the detected indications at said second location, thereby to provide a more accurate measurement of the intrinsic value of said selected neutron characteristic.
Claim 23
Independent Claim
213 words
A method for providing verifiably accurate logging data derived at least in part by neutron logging of earth formation characteristics, comprising the steps of: irradiating an earth formation with discrete pulses of high-energy neutrons, the decay of which is functionally related to intrinsic neutron characteristics of the formation; detecting indications of the neutron population in the formation between neutron pulses at a first location speed from the neutron source; deriving a representation of an apparent value of a selected one of said neutron characteristics corresponding to the detected indications at the first location; detecting indications of the neutron population in the formation between neutron pulses at a second location spaced from the first location and from the neutron source; combining said first location apparent value representation and a function of said second location detected indications to derive a representation functionally related to the quality of said first location apparent value representation as a measurement of the intrinsic value of said selected neutron characteristic; and combining said first location apparent value representation and said quality representation to derive a representation of an apparent value of said selected neutron characteristic corresponding to the detected indications at said second location, thereby to provide a more accurate measurement of the intrinsic value of said selected neutron characteristic.
Claim 24
Dependent Claim
19 words
The method of claim 20 wherein said selected neutron characteristic is a thermal neutron absorption characteristic of the formation.
Claim 25
Dependent Claim
36 words
The method of claim 20 further Comprising the step of recording one or more of said first location apparent value representation, said quality representation, and said second location apparent value representation as a function of depth.
Claim 26
Dependent Claim
118 words
The method of claim 20 wherein: the first location apparent value representation deriving step comprises measuring the neutron population in the formation at said first location in response to first location detected indications occurring during a variable measurement period following a neutron pulse and deriving said apparent value representation from said neutron population measurement; and said first location apparent value representation and said second location detected indications function combining step comprises controlling the timing of the measurement period following a subsequent neutron pulse as a function of said first location apparent value representation and measuring the neutron population in the formation at said second location in response to second location detected indications occurring during said controlled measurement period.
Claim 27
Dependent Claim
207 words
Apparatus for providing verifiably accurate logging data derived at least in part by neutron logging of eargh formation characteristics, comprising: a source for irradiating an earth formation with discrete pulses of high-energy neutrons to produce therein between pulses a population of neutrons, the decoy of which is functionally related to intrinsic neutron characteristics of the formation; means for detecting indications of the neutron population in the formation between neutron pulses at a first location spaced from the neutron source; means for deriving a representation of an apparent value of a selected one of said neutron characteristics corresponding to the detected indications at the first location; means for detecting indications of the neutron population in the formation between neutron pulses at a second location spaced from the first location and from the neutron source; and means for combining said first location apparent value representation and a function of said second location detected indications to derive representation functionally related to a quotient of the apparent values of said selected neutron characteristic corresponding to the detected indications at the first and second locations, thereby to provide information as to the validity of said first location apparent value representation as a measurement of the intrinsic value of said selected neutron characteristic.
Claim 28
Dependent Claim
207 words
Apparatus for providing verifiably accurate logging data derived at least in part by neutron logging of eargh formation characteristics, comprising: a source for irradiating an earth formation with discrete pulses of high-energy neutrons to produce therein between pulses a population of neutrons, the decoy of which is functionally related to intrinsic neutron characteristics of the formation; means for detecting indications of the neutron population in the formation between neutron pulses at a first location spaced from the neutron source; means for deriving a representation of an apparent value of a selected one of said neutron characteristics corresponding to the detected indications at the first location; means for detecting indications of the neutron population in the formation between neutron pulses at a second location spaced from the first location and from the neutron source; and means for combining said first location apparent value representation and a function of said second location detected indications to derive representation functionally related to a quotient of the apparent values of said selected neutron characteristic corresponding to the detected indications at the first and second locations, thereby to provide information as to the validity of said first location apparent value representation as a measurement of the intrinsic value of said selected neutron characteristic.
Claim 29
Dependent Claim
19 words
The apparatus of claim 24 wherein said selected neutron characteristic is a thermal neutron absorption characteristic of the formation.
Claim 30
Dependent Claim
18 words
The apparatus of claim 24 further comprising means for recording said quotient-related representation as a function of depth.
Claim 31
Dependent Claim
40 words
The apparatus of claim 24 further comprising means for combining a function of said first location apparent value representation and a function of said quotient-related representation to provide a corrected representation of the intrinsic value of said selected neutron characteristic.
Claim 32
Dependent Claim
54 words
The apparatus of claim 27 further comprising: means for recording said first location apparent value representation as a function of depth at least so long as said quotient-related representation is greater than a predetermined value; and means for recording said corrected representation at least when said quotient-related representation is less than said predetermined value.
Claim 33
Dependent Claim
48 words
The apparatus of claim 24 wherein said combining means comprises: means for deriving a representation of an apparent value of said selected neutron characteristic corresponding to the detected indications at said second location; and means for forming the ratio of said first and second location apparent value representations.
Claim 34
Dependent Claim
103 words
The apparatus of claim 23 wherein: said first location apparent value representation deriving means comprises means for measuring the neutron population in the formation at said first location iN response to first location detected indications occurring during a measurement period following a neutron pulse and means for deriving said apparent value representation from said neutron population measurement; and said combining means comprises means for controlling the timing of the measurement period following a subsequent neutron pulse as a function of said apparent value representation and means for measuring the neutron population in the formation at said second location during said controlled measurement period.
Claim 35
Dependent Claim
245 words
The apparatus of claim 30 wherein: the means for measuring the neutron population at the first location comprises means for measuring the neutron population during each of first and second time intervals within the measurement period following said neutron pulse; the means for deriving said apparent value representation corresponding to the neutron population measurement at the first location comprises means for forming the ratio of the neutron population measurements during the first and second time intervals and for determining the timings of the first and second intervals required to maintain the neutron population ratio substantially at a predetermined number, the duration thus determined of at least one of the first and second intervals providing a representation of an apparent value of said selected neutron characteristic; the means for controlling the timing of the measurement period following a subsequent neutron pulse comprises means for equating the timings of first and second time intervals within said subsequent measurement period to those required to maintain said neutron populations ratio substantially at said predetermined number; the means for measuring the neutron population at the second location comprises means for measuring the neutron population during each of the first and second intervals of said subsequent measurement period; and the means for deriving a representation functionally related to a quotient of said apparent values comprises means for forming the ratio of the neutron population measurements at the second location during the first and second time intervals of said subsequent measurement period.
Claim 36
Dependent Claim
45 words
The apparatus of claim 31 further comprising means for correcting said first location apparent value representation by a function of said ratio of the neutron population measurements at the second location to provide a corrected representation of the intrinsic value of said selected neutron characteristic.
Claim 37
Dependent Claim
57 words
The apparatus of claim 31 further comprising means for combining a function of said first location apparent value representation and a function of said ratio of the neutron population measurements at the second location to provide a representation of the apparent value of said selected neutron characteristic corresponding to the neutron population measurement at the second location.
Claim 38
Dependent Claim
41 words
The apparatus of claim 33 wherein the means for measuring the neutron populations at the first and second locations comprise first and second radiation detectors, respectively, the first detector being spaced closer to the neutron source than is the second detector.
Claim 39
Dependent Claim
221 words
Apparatus for providing verifiably accurate logging data derived at least in part by neutron logging of earth formations, comprising: a source for irradiating an earth formation with discrete pulses of high-energy neutrons, the decay of which is functionally related to intrinsic neutron characteristics of the formation; means for detecting indications of the neutron population in the formation between neutron pulses at a first location spaced from the neutron source; means for deriving a representation of an apparent value of a selected one of said neutron characteristics corresponding to the detected indications at the first location; means for detecting indications of the neutron population in the formation between neutron pulses at a second location spaced from the first location and from the neutron souRce; means for combining said first location apparent value representation and a function of said second location detected indications to derive a representation functionally related to the quality of said first location apparent value representation as a measurement of the intrinsic value of said selected neutron characteristic; and means for combining said first location apparent value representation and said quality representation to derive a representation of an apparent value of said selected neutron characteristic corresponding to the detected indications at said second location, thereby to provide a more accurate measurement of the intrinsic value of said selected neutron characteristic.
Claim 40
Dependent Claim
221 words
Apparatus for providing verifiably accurate logging data derived at least in part by neutron logging of earth formations, comprising: a source for irradiating an earth formation with discrete pulses of high-energy neutrons, the decay of which is functionally related to intrinsic neutron characteristics of the formation; means for detecting indications of the neutron population in the formation between neutron pulses at a first location spaced from the neutron source; means for deriving a representation of an apparent value of a selected one of said neutron characteristics corresponding to the detected indications at the first location; means for detecting indications of the neutron population in the formation between neutron pulses at a second location spaced from the first location and from the neutron souRce; means for combining said first location apparent value representation and a function of said second location detected indications to derive a representation functionally related to the quality of said first location apparent value representation as a measurement of the intrinsic value of said selected neutron characteristic; and means for combining said first location apparent value representation and said quality representation to derive a representation of an apparent value of said selected neutron characteristic corresponding to the detected indications at said second location, thereby to provide a more accurate measurement of the intrinsic value of said selected neutron characteristic.
Claim 41
Dependent Claim
19 words
The apparatus of claim 35 wherein said selected neutron characteristic is a thermal neutron absorption characteristic of the formation.
Claim 42
Dependent Claim
35 words
The apparatus of claim 35 further comprising means for recording one or more of said first location apparent value representation, said quality representation, and said second location apparent value representation as a function of depth.
Claim 43
Dependent Claim
130 words
The apparatus of claim 35 wherein: the first location apparent value representation deriving means comprises means for measuring the neutron population in the formation at said first location in response to first location detected indications occurring during a variable measurement period following a neutron pulse and means for deriving said apparent value representation from said neutron population measurement; and said means for combining said first location apparent value representation and a function of said second location detected indications comprises means for controlling the timing of the measurement period following a subsequent neutron pulse as a function of said first location apparent value represenation and means for measuring the neutron population in the formation at said second location in response to second location detected indications occurring during said controlled measurement period.
Claim 44
Independent Claim
142 words
A method for deriving a verifiably accurate measurement of an intrinsic neutron characteristic of an earth formation traversed by a borehole from detected indications of the neutron populations in the formation at first and second spaced locations along the borehole following irradiation of the formation with pulses of neutrons, comprising the steps of: deriving a representation of an apparent value of said neutron characteristic corresponding to said first location detected indications; and combining said first location apparent value representation and a function of said second location detected indications to derive a representation functionally related to a quotient of the apparent values of said neutron characteristic corresponding to the detected indications at the first and second locations, thereby to provide information as to the validity of said first location apparent value representation as a measurement of the intrinsic value of said neutron characteristic.
Claim 45
Independent Claim
142 words
A method for deriving a verifiably accurate measurement of an intrinsic neutron characteristic of an earth formation traversed by a borehole from detected indications of the neutron populations in the formation at first and second spaced locations along the borehole following irradiation of the formation with pulses of neutrons, comprising the steps of: deriving a representation of an apparent value of said neutron characteristic corresponding to said first location detected indications; and combining said first location apparent value representation and a function of said second location detected indications to derive a representation functionally related to a quotient of the apparent values of said neutron characteristic corresponding to the detected indications at the first and second locations, thereby to provide information as to the validity of said first location apparent value representation as a measurement of the intrinsic value of said neutron characteristic.
Claim 46
Dependent Claim
41 words
The method of claim 39 wherein said combining step comprises: deriving a representation of an apparent value of said neutron characteristic corresponding to said second location detected indications; and forming a ratio of the first and second location apparent value representations.
Claim 47
Dependent Claim
103 words
The method of claim 39 wherein: said first location apparent value representation deriving step comprises measuring the neutron population in the formation at said first location in response to first location detected indications occurring during a measurement period following a neutron pulse and deriving said apparent value representation from said neutron population measurement; and said combining step comprises controlling the timing of the measurement period following a subsequent neutron pulse as a function of said apparent value representation and measuring the neutron population in the formation at said second location in response to second location detected indicatIons occurring during said controlled measurement period.
Claim 48
Dependent Claim
37 words
The method of claim 39 further comprising combining said first location apparent value representation and said quotient-related representation to provide a representation of an apparent value of said neutron characteristic corresponding to said second location detected indications.
Claim 49
Independent Claim
188 words
A method for providing a measurement of an intrinsic neutron characteristic of an earth formation traversed by a borehole from detected indications of the neutron populations in the formation at first and second spaced locations along the borehole following irradiation of the formation with pulses of neutrons, comprising the steps of: deriving neutron population measurements from first location detected indications occurring during a measurement period between neutron pulses; deriving a representation of an apparent value of said neutron characteristic corresponding to said first location neutron population measurements; deriving neutron population measurements from second location detected indications occurring during a measurement period between neutron pulses; combining said first location apparent value representation and a function of said second location neutron population measurements to derive a representation related to a function of the apparent values of said neutron characteristic corresponding to said first and second neutron population measurements; and combining said first location apparent value representation and said representation related to a function of the first and second apparent values to derive a representation of an apparent value of said neutron characteristic corresponding to the second location neutron population measurements.
Claim 50
Independent Claim
188 words
A method for providing a measurement of an intrinsic neutron characteristic of an earth formation traversed by a borehole from detected indications of the neutron populations in the formation at first and second spaced locations along the borehole following irradiation of the formation with pulses of neutrons, comprising the steps of: deriving neutron population measurements from first location detected indications occurring during a measurement period between neutron pulses; deriving a representation of an apparent value of said neutron characteristic corresponding to said first location neutron population measurements; deriving neutron population measurements from second location detected indications occurring during a measurement period between neutron pulses; combining said first location apparent value representation and a function of said second location neutron population measurements to derive a representation related to a function of the apparent values of said neutron characteristic corresponding to said first and second neutron population measurements; and combining said first location apparent value representation and said representation related to a function of the first and second apparent values to derive a representation of an apparent value of said neutron characteristic corresponding to the second location neutron population measurements.
Claim 51
Dependent Claim
18 words
The method of claim 43 wherein said neutron characteristic is a thermal neutron absorption characteristic of the formation.
Claim 52
Dependent Claim
131 words
The method of claim 43 wherein: the step of deriving said first location apparent value representation comprises controlling the timing of first and second detection intervals within the measurement period as a function of said apparent value representation; the step of combining said first location apparent value representation and a function of said second location neutron population measurements comprises controlling the measuring of the neutron population at the second location so as to provide a measurement of the neutron population at said second location during each of said first and second detection intervals; and the function of said second location neutron population measurements combined with said first location apparent value representation is a function of the ratio of the first and second detection interval neutron population measurements at the second location.
Claim 53
Dependent Claim
54 words
The method of claim 45 wherein the representation derived by combining said first location apparent value representation and said ratio function of the second location neutron population measurements is related to the ratio of the apparent values of said selected neutron characteristic corresponding to the neutron population measurements at said first and second locations.
Claim 54
Independent Claim
163 words
A method for providing a verifiably accurate measurement of an intrinsic neutron characteristic of an earth formation traversed by a borehole from detected indications of the neutron populations in the formation at first and second spaced locations along the borehole following irradiation of the formation with pulses of neutrons, comprising the steps of: deriving a representation of an apparent value of said neutron characteristic corresponding to said first location detected indications; combining said first location apparent value representation and a function of said second location detected indications to derive a representation functionally related to the quality of said first location apparent value representation as a measurement of the intrinsic value of said neutron characteristic; and combining said first location apparent value representation and said quality representation to derive a representation of an apparent value of said neutron characteristic corresponding to the detected indications at said second location, thereby to provide a more accurate measurement of the intrinsic value of said selected neutron characteristic.
Claim 55
Independent Claim
163 words
A method for providing a verifiably accurate measurement of an intrinsic neutron characteristic of an earth formation traversed by a borehole from detected indications of the neutron populations in the formation at first and second spaced locations along the borehole following irradiation of the formation with pulses of neutrons, comprising the steps of: deriving a representation of an apparent value of said neutron characteristic corresponding to said first location detected indications; combining said first location apparent value representation and a function of said second location detected indications to derive a representation functionally related to the quality of said first location apparent value representation as a measurement of the intrinsic value of said neutron characteristic; and combining said first location apparent value representation and said quality representation to derive a representation of an apparent value of said neutron characteristic corresponding to the detected indications at said second location, thereby to provide a more accurate measurement of the intrinsic value of said selected neutron characteristic.
References Cited (Backward Citations)
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| 3.5 Years (Year 4) | 1978-06-16 | 1978-12-16 | 1979-06-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-06-16 | 1982-12-16 | 1983-06-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-06-16 | 1986-12-16 | 1987-06-17 | $7700.00 | Window Closed / Lapsed |