CN111337991A - Uranium ore epithermal neutron correction algorithm based on double neutron detectors - Google Patents
Uranium ore epithermal neutron correction algorithm based on double neutron detectors Download PDFInfo
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- G01V5/00—Prospecting or detecting by the use of nuclear radiation, e.g. of natural or induced radioactivity
- G01V5/04—Prospecting or detecting by the use of nuclear radiation, e.g. of natural or induced radioactivity specially adapted for well-logging
- G01V5/08—Prospecting or detecting by the use of nuclear radiation, e.g. of natural or induced radioactivity specially adapted for well-logging using primary nuclear radiation sources or X-rays
- G01V5/10—Prospecting or detecting by the use of nuclear radiation, e.g. of natural or induced radioactivity specially adapted for well-logging using primary nuclear radiation sources or X-rays using neutron sources
Abstract
The invention discloses a uranium mine epithermal neutron correction algorithm based on a dual-neutron detector, which is mainly aimed at correcting an epithermal neutron attenuation time spectrum of uranium fission prompt neutron logging, constructs a uranium-bearing sandstone formation numerical model based on interaction of neutrons and formation nuclides and a physical mechanism of formation uranium fission, researches a change rule of thermal neutrons under different neutron fluxes and formation water-containing conditions by means of a standard model well, and can eliminate the influence of the dual-neutron detector flux on the epithermal neutron counting rate, thereby improving the interpretation precision of uranium content to a certain extent.
Description
Technical Field
The invention belongs to a pulse neutron logging technology of uranium ore exploration drilling, and particularly relates to a uranium ore epithermal neutron correction algorithm based on a dual neutron detector.
Background
The uranium fission prompt neutron logging is a uranium ore quantitative technology for directly measuring uranium in uranium ore exploration by utilizing thermal neutrons to initiate 235U fission and detecting neutrons released by 235U fission in stratum rocks. The uranium fission-based prompt neutron logging technology is mainly applied to the field of uranium mine exploration, is still controlled by western developed countries such as America and the like at present, belongs to a high-end nuclear logging technology, and is limited to export to China. In the research field of uranium ore pulsed neutron logging, in 1961, a logging discussion about neutron-fission neutrons of uranium is internationally available; in the following research, the theory of uranium mine logging is continuously perfected and put forward to practical application, in recent years, developed countries such as america and russia have developed new technologies such as prompt neutron logging and slow neutron logging based on uranium (235U) fission, wherein the uranium mine pulse neutron logging technology approaches or reaches a practical level, and direct uranium logging and uranium mine quantification are realized. The Australian uranium mining exploration company obtains the production right and the sales right of the uranium quantitative pulse neutron logging instrument from the United states through patent transfer, and is actively engaged in research work in the aspect; in 2012, Penney, r, etc. compared neutron logging with gamma logging for explanation, fully determined the advantages of neutron logging. In China, the research and application of pulsed neutron logging in the field of oil exploration is mature, but the pulsed neutron logging just starts in the field of uranium ore exploration. In the aspect of theoretical research, the basic theories of Tangbin, Zhang Feng, Zhang Long Yun and the like are discussed, researched and summarized; wangxingguang utilizes Monte Carlo to simulate the response of PNFN under the conditions of strata with different uranium contents and different stratum porosities, and explains the relationship between prompt fission epithermal neutrons and delayed fission thermal neutrons and the stratum uranium contents and the porosity. In the aspect of practice, a leading team of the teaching of Taxin university of eastern Hua rational and university obtains primary success under the support of the relevant ministry of China, the first neutron logging uranium logging system in China is developed, the system adopts a multi-detector technology, and then uranium ore is directly measured, and the rapid uranium logging on site is realized. In view of the restriction of the research and development technology of domestic instruments, the distance between the research level and the international research level and the requirement (0.01%) of the technical standard of China is certain.
In a word, currently, uranium ore pulsed neutron logging is relatively mature abroad, logging instruments are produced and put into production practice in the united states and russia, due to the reason of technical secrecy, the latest theoretical research result cannot be obtained through a public way, the research of uranium ore measurement by using an instantaneous neutron logging technology is emphasized by experts in the field in China, and the national support of the field is continuously strengthened in recent years. The uranium ore epithermal neutron correction algorithm based on the dual neutron detector is an important research content in the field, and is expected to improve the accuracy of uranium content explanation and expand the application range of the prompt fission neutron logging instrument under the condition of the prior art in China.
Disclosure of Invention
The invention aims to provide a uranium ore epithermal neutron correction algorithm based on a double-neutron detector, aiming at the technical problems that the decay time spectrum of thermal neutrons can be directly influenced due to different stratum components and environments, the change of the counting rate of the thermal neutrons and the change of elapsed time in a decay curve are reflected, the total number of the thermal neutrons can directly influence the total count of the epithermal neutrons, and the accuracy of uranium content explanation by utilizing the total count of the epithermal neutrons is further influenced.
The technical scheme adopted by the invention is as follows:
a uranium ore epithermal neutron correction algorithm based on a dual neutron detector comprises the following steps:
step S1: detecting instantaneous epithermal neutrons by using a double-neutron detector to obtain a time attenuation spectrogram and an instantaneous epithermal neutron total count;
step S2: correcting the obtained instantaneous epithermal neutron time attenuation spectrogram;
step S3: and analyzing the uranium content by combining the temporal attenuation spectrogram of the prompt epithermal neutrons corrected in the step S2 with the total count of the prompt epithermal neutrons.
Preferably, in step S2, the specific correction method includes the steps of:
step S21: selecting a standard thermal neutron time attenuation spectrogram as a correction standard,record as
Wherein, a0In order to be able to obtain a damping constant,
tau is the thermal neutron lifetime, t is the decay time;
step S22: when the uranium content is explained, the epithermal neutron attenuation curve needs to be integrated, and a mode of summing discrete counting rates is generally adopted, so that the correction of a transient epithermal neutron time attenuation spectrogram can be converted into the epithermal neutron total count of a specified interval for correction, the epithermal neutron total count on a certain interval of the attenuation spectrogram is an important parameter (conversion coefficient) for uranium content explanation, and the epithermal neutron total count and the thermal neutron total count meet the following requirements:
wherein, aiNormal ripening for a specific uranium content, NEIs the total count of epithermal neutrons, NTIs the total count of thermal neutrons;
suppose that the total epithermal neutron count to be corrected is NiCorresponding to an epithermal neutron attenuation spectrum of
The corrected total epithermal neutron count is as follows:
in the above formula:
Nifor the epithermal neutron count rate measured for actual logging,
N'ifor the corrected epithermal neutron count rate,
a0,b0is the coefficient in the epithermal neutron curve attenuation equation of the standard model well scale,
ai,biis measured forThe coefficients in the epithermal neutron curve attenuation equation,
τifor the thermal neutron lifetime of the actual log,
τ0is the thermal neutron lifetime of a standard model well scale,
preferably, in step S21, the standard thermal neutron time attenuation spectrum may be obtained by using a dual neutron detector to perform long-time measurement on an ideal standard model and then scaling.
The invention has the beneficial effects that: the correction algorithm for the epithermal neutron curve of the uranium fission prompt neutron logging can eliminate partial influence of flux of a neutron generator on the epithermal neutron curve, so that the interpretation precision of the uranium content is improved to a certain extent.
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In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a graph (logarithmic scale) of Monte Carr simulation results of different fluxes of neutron generators;
FIG. 2 is a graph of standard model epithermal and thermal neutrons.
Detailed Description
The following examples may assist those skilled in the art in a more complete understanding of the present invention, but are not intended to limit the invention in any way.
A uranium mine logging method based on a dual-neutron detector has the basic principle that fast neutrons, namely primary neutrons, are emitted to stratum rock in a pulse mode in a drill hole, the primary neutrons are moderated into thermal neutrons, the thermal neutrons induce U-235 fission, and uranium fission prompt neutrons, namely secondary neutrons, are emitted. The primary neutrons and the secondary neutrons are all slowed down into the epithermal neutrons and the thermal neutrons along with time, and the uranium fission prompt neutrons prolong the elapsed time of the epithermal neutrons, so that the method is a physical basis for detecting uranium fission and uranium quantification. And (3) extracting and expressing the moderating capability of the primary neutrons and the fission persistence capability of the thermal neutrons and the thermal neutrons by recording the epithermal neutrons and the thermal neutrons time spectrum, so as to construct a stratum rock uranium quantitative algorithm.
According to the attenuation theory of neutrons in the stratum, the neutron nuclear fusion energy-saving device presents a negative exponential attenuation law, and the total count of uranium fission prompt neutrons moderated into epithermal neutrons in a certain interval is in direct proportion to the uranium content. However, in the actual logging experiment process, it is found that the decay time spectrum of the thermal neutrons can be directly influenced due to different formation components and environments, the change of the counting rate of the thermal neutrons and the change of the elapsed time in a decay curve are reflected, the total number of the thermal neutrons can directly influence the total count of the epithermal neutrons, and the accuracy of uranium content explanation by utilizing the total count of the epithermal neutrons is further influenced.
As shown in fig. 1, the color diagram thereof can refer to fig. 1 in the substantive review reference, neutron attenuation curves of neutron generators with different fluxes simulated by using monte carlo simulation method in the same uranium content model, and the neutron flux value of the numerical monte carlo simulation represented by the scientific counting method behind the right-hand graph in fig. 2, it can be seen that when the flux of the neutron generator is reduced, the thermal neutron count rate is reduced, and at the same time, the epithermal neutron count rate is also reduced, and in order to be able to explain the uranium content by using the epithermal neutrons, the data needs to be corrected.
In order to eliminate the influence that the thermal neutron attenuation curve that environment and hardware factor caused is drawn low, and then produces uranium content explanation, this application provides a uranium ore epithermal neutron correction algorithm based on two neutron detectors, includes following step:
step S1: detecting instantaneous epithermal neutrons by using a double-neutron detector to obtain a time attenuation spectrogram and an instantaneous epithermal neutron total count;
step S2: correcting the obtained instantaneous epithermal neutron time attenuation spectrogram; the correction method comprises the following steps:
step S21: selecting a standard thermal neutron time attenuation spectrogram as a correction standard, wherein the standard thermal neutron time attenuation spectrogram can be obtained by performing long-time measurement on an ideal standard model by using a dual-neutron detector and then is graduated and recorded as
Wherein, a0In order to be able to obtain a damping constant,
tau is the thermal neutron lifetime, t is the decay time;
step S22: when the uranium content is explained, the epithermal neutron attenuation curve needs to be integrated, and a mode of summing discrete counting rates is generally adopted, so that the correction of a transient epithermal neutron time attenuation spectrogram can be converted into the epithermal neutron total count of a specified interval for correction, the epithermal neutron total count on a certain interval of the attenuation spectrogram is an important parameter (conversion coefficient) for uranium content explanation, and the epithermal neutron total count and the thermal neutron total count meet the following requirements:
wherein, aiNormal ripening for a specific uranium content, NEIs the total count of epithermal neutrons, NTIs the total count of thermal neutrons;
suppose that the total epithermal neutron count to be corrected is NiCorresponding to an epithermal neutron attenuation spectrum of
The corrected total epithermal neutron count is as follows:
in the above formula:
Nifor the epithermal neutron count rate measured for actual logging,
N'ifor the corrected epithermal neutron count rate,
a0,b0is the coefficient in the epithermal neutron curve attenuation equation of the standard model well scale,
ai,bifor the coefficients in the measured epithermal neutron curve attenuation equation,
τifor the thermal neutron lifetime of the actual log,
τ0is the thermal neutron lifetime of a standard model well scale,
step S3: and analyzing the uranium content by combining the temporal attenuation spectrogram of the prompt epithermal neutrons corrected in the step S2 with the total count of the prompt epithermal neutrons.
The correction algorithm of the invention carries out verification experiments on a standard model well, the experimental model comprises a plurality of standard models with different contents, a measuring result curve is shown in figure 2, a color chart of the experimental model can refer to figure 2 in a substantial examination reference material, and data in the figure can show that neutron attenuation curves measured by the models with different contents at different times (neutron flux changes) are different, and the corresponding thermal neutron curves have obvious deviation, which inevitably causes the change of the epithermal neutron curves and finally influences the interpretation precision of uranium content.
The verification process of the correction algorithm in the standard model is as follows:
firstly, a new double neutron detector is utilized to carry out long-time measurement (generally 3 minutes) on a standard model to obtain a group of standard thermal neutron and epithermal neutron curves (time attenuation spectrogram), and a is obtained after curve fitting0,b0The logging tool described above was then used in other experiments, after a period of use, the neutron flux had already beenAfter a certain degree of decline, the logging instrument is used for measuring a standard model to obtain a curve with reduced neutron flux, and finally the algorithm is used for correction verification, and the corrected total count of the epithermal neutrons can be used for explaining the uranium content. The method is characterized in that a total count mode of the epithermal neutrons is adopted to explain the uranium content, a correction algorithm of the epithermal neutron time attenuation spectrogram of the uranium fission prompt neutron logging is used to correct the epithermal neutron time attenuation spectrogram, errors of the epithermal neutron time attenuation spectrogram are reduced to different degrees after correction and compared with the real content of a standard model, as shown in table 1, the explanation error of the model content with the uranium content of 0.6% is reduced from-2.590% to-1.758%, and the explanation error of the model content with the uranium content of 0.9% is reduced from 1.158% to 0.743%.
TABLE 1 comparative table of interpretation errors of count correction and uncorrected content of epithermal neutrons
In addition, the uranium fission prompt neutron logging epithermal neutron curve correction algorithm is applied to a Chinese uranium fission prompt neutron logging instrument, and is compared with a Russian neutron logging instrument data processing method.
The following group of data comparison (see table 2) is from the inspection result of the russian pulse neutron logging instrument and the content interpretation result of the chinese logging instrument, and due to the structural difference between the two instruments, a certain difference also exists in the final data processing algorithm, namely, the difference between the two epithermal neutron attenuation time spectrum curve correction algorithms is obtained, and the epithermal neutron attenuation time spectrum curve correction in the uranium content interpretation algorithm in table 2 is completed by using the two algorithms. The interpretation error of the uranium content in table 2 is different because different epithermal neutron decay time spectrum curve correction algorithms are used in different instruments.
TABLE 2 comparison of content interpretation errors for two tools tested on the same model
From the errors in table 2, the interpretation accuracy of the uranium content of the two logging instruments on the same model reaches the industrial standard, but the uranium fission prompt neutron logging instrument independently developed in china has a slightly higher accuracy than the russian pulse neutron logging instrument.
Claims (3)
1. A uranium ore epithermal neutron correction algorithm based on a dual neutron detector is characterized by comprising the following steps:
step S1: detecting instantaneous epithermal neutrons by using a double-neutron detector to obtain a time attenuation spectrogram and an instantaneous epithermal neutron total count;
step S2: correcting the obtained instantaneous epithermal neutron time attenuation spectrogram;
step S3: and analyzing the uranium content by combining the temporal attenuation spectrogram of the prompt epithermal neutrons corrected in the step S2 with the total count of the prompt epithermal neutrons.
2. The dual neutron detector-based uranium ore epithermal neutron correction algorithm according to claim 1, wherein in the step S2, the specific correction method comprises the following steps:
step S21: selecting a standard thermal neutron time attenuation spectrogram as a correction standard and recording the standard thermal neutron time attenuation spectrogram as a correction standard
Wherein, a0In order to be able to obtain a damping constant,
tau is the thermal neutron lifetime, t is the decay time;
step S22: when the uranium content is explained, the epithermal neutron attenuation curve needs to be integrated, and a mode of summing discrete counting rates is generally adopted, so that the correction of a transient epithermal neutron time attenuation spectrogram can be converted into the epithermal neutron total count of a specified interval for correction, the epithermal neutron total count on a certain interval of the attenuation spectrogram is an important parameter for explaining the uranium content, and the epithermal neutron total count and the thermal neutron total count meet the following requirements:
wherein, aiNormal ripening for a specific uranium content, NEIs the total count of epithermal neutrons, NTIs the total count of thermal neutrons;
suppose that the total epithermal neutron count to be corrected is NiCorresponding to an epithermal neutron attenuation spectrum of
The corrected total epithermal neutron count is as follows:
in the above formula:
Nifor the epithermal neutron count rate measured for actual logging,
Ni' is the corrected epithermal neutron count rate,
a0,b0is the coefficient in the epithermal neutron curve attenuation equation of the standard model well scale,
ai,bifor the coefficients in the measured epithermal neutron curve attenuation equation,
τifor the thermal neutron lifetime of the actual log,
τ0is the thermal neutron lifetime of a standard model well scale,
。
3. the dual neutron detector-based uranium ore epithermal neutron correction algorithm according to claim 1, wherein in the step S21, the standard thermal neutron time attenuation spectrum is calibrated by using a dual neutron detector to perform long-time measurement on an ideal standard model.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111859675A (en) * | 2020-07-23 | 2020-10-30 | 东华理工大学 | Slurry density correction method based on uranium fission prompt neutron logging data |
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Patent Citations (4)
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| US4350887A (en) * | 1980-11-05 | 1982-09-21 | The United States Of America As Represented By The United States Department Of Energy | Method of assaying uranium with prompt fission and thermal neutron borehole logging adjusted by borehole physical characteristics |
| CN104074501A (en) * | 2013-03-29 | 2014-10-01 | 核工业航测遥感中心 | Fission neutron well logging correction method |
| CN103470252A (en) * | 2013-09-13 | 2013-12-25 | 东华理工大学 | Prompt neutron logging and uranium ore quantity determining technology based on above-thermal neutron time spectrum |
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| XIN-GUANG WANG ET AL.: "A novel pulsed neutron uranium logging instrument with two epithermal neutron detectors", 《SEG NEW ORLEANS ANNUAL MEETING》 * |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111859675A (en) * | 2020-07-23 | 2020-10-30 | 东华理工大学 | Slurry density correction method based on uranium fission prompt neutron logging data |
| CN111859675B (en) * | 2020-07-23 | 2022-09-13 | 东华理工大学 | Slurry density correction method based on uranium fission prompt neutron logging data |
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