阅读说明：本技术 一种基于能谱测井交叉谱段的铀矿定量剥离系数求法 (Uranium ore quantitative stripping coefficient solving method based on energy spectrum logging cross spectrum section ) 是由 王海涛 汤彬 王仁波 刘志锋 黄凡 张丽娇 周书民 张雄杰 张焱 陈锐 刘琦 于 2020-11-24 设计创作，主要内容包括：本发明公开了一种基于能谱测井交叉谱段的铀矿定量剥离系数求法。剥离系数可表示为将单位含量的其它元素在某个特征谱段产生的计数率剥离掉的系数。本发明所述基于能谱测井交叉谱段的铀矿定量剥离系数求法是以自然伽马能谱曲线中钍、铀-镭、钾元素所对应的特征峰为对象,将自然伽马能谱曲线划分为多个相互交叉的特征谱段,求得单位含量的不同元素在某个特征谱段的计数率,两种元素在该特征谱段计数率的比值即为剥离系数。本发明所述基于能谱测井交叉谱段的铀矿定量剥离系数求法,可在确保钍、铀-镭、钾三种自然伽马放射性元素含量解释精度的同时,使自然伽马能谱测井的速度达到与自然伽马总量测井相当的水平。(The invention discloses a uranium ore quantitative stripping coefficient calculation method based on an energy spectrum logging cross spectrum section. The stripping factor can be expressed as a factor that strips off the count rate produced by other elements of the unit content in a certain characteristic spectral band. The method for determining the quantitative stripping coefficient of the uranium ore based on the energy spectrum logging cross spectrum section takes characteristic peaks corresponding to elements of thorium, uranium-radium and potassium in a natural gamma energy spectrum curve as objects, the natural gamma energy spectrum curve is divided into a plurality of mutually crossed characteristic spectrum sections, the counting rates of different elements with unit content in a certain characteristic spectrum section are obtained, and the ratio of the counting rates of the two elements in the characteristic spectrum section is the stripping coefficient. The uranium ore quantitative stripping coefficient solving method based on the energy spectrum logging cross-spectral band can ensure the interpretation precision of the contents of three natural gamma radioactive elements of thorium, uranium-radium and potassium, and simultaneously enables the logging speed of the natural gamma energy spectrum to reach the level equivalent to the logging speed of the natural gamma total amount.)

1. A uranium ore quantitative stripping coefficient solving method based on an energy spectrum logging cross-spectral band comprises the following steps:

(1) according to the positions of the characteristic peaks of different radioactive elements, a natural gamma energy spectrum curve is divided into a plurality of mutually crossed characteristic spectrum sections:

1) selecting i characteristic peaks of thorium, dividing into corresponding i thorium characteristic spectrum sections, wherein the energy range of gamma ray of each characteristic spectrum section is from 400keV to the corresponding characteristic peak, and at least one characteristic spectrum section should contain thorium characteristic peak with energy of 2.62MeV from 400keV,

2) selecting j characteristic peaks of a uranium-radium system, dividing the characteristic peaks into corresponding j characteristic spectrum sections of the uranium-radium system, wherein the energy range of gamma rays of each characteristic spectrum section is from 400keV to the corresponding characteristic peak, at least one characteristic spectrum section comprises the characteristic peaks of the uranium-radium system with the energy of 400keV to 1.76MeV,

3) selecting k characteristic peaks of a potassium system, dividing the k characteristic peaks into corresponding k potassium system characteristic spectrum segments, wherein the gamma ray energy range of each characteristic spectrum segment is from 400keV to the corresponding characteristic peak, and at least one characteristic spectrum segment comprises the potassium system characteristic peak with the energy of 400keV to 1.46 MeV;

(2) calculating the counting rate of each characteristic spectrum segment of thorium series, uranium-radium series and potassium series on a natural gamma radioactive standard model:

1) calculating the counting rate of thorium characteristic spectrum on a natural gamma radioactive background standard modelCounting rate of characteristic spectrum section of uranium-radium systemCounting rate of characteristic spectrum band of potassium series

2) At a nominal content of Q_ThThe counting rate of each characteristic spectrum section corresponding to the thorium element is calculated on a natural gamma radioactive thorium element standard model

At a nominal content of Q_ThThe counting rate of each characteristic spectrum section corresponding to the uranium-radium element is calculated on a natural gamma radioactive thorium element standard model

At a nominal content of Q_ThCalculating each corresponding to potassium element on natural gamma radioactive thorium element standard modelCount rate of characteristic spectral band

3) At a nominal content of Q_UThe counting rate of each characteristic spectrum section corresponding to the thorium element is calculated on the natural gamma radioactive uranium element standard model

At a nominal content of Q_UThe counting rate of each characteristic spectrum section corresponding to the uranium-radium element is solved on the natural gamma radioactive uranium element standard model

At a nominal content of Q_UThe counting rate of each characteristic spectrum section corresponding to the potassium element is obtained on the natural gamma radioactive uranium element standard model

4) At a nominal content of Q_KThe counting rate of each characteristic spectrum section corresponding to the thorium element is calculated on a natural gamma radioactive potassium element standard model

At a nominal content of Q_KThe counting rate of each characteristic spectrum section corresponding to the uranium-radium element is solved on a natural gamma radioactive potassium element standard model

At a nominal content of Q_KThe counting rate of each characteristic spectrum section corresponding to the potassium element is obtained on the natural gamma radioactive potassium element standard model

(3) And (3) solving a natural gamma energy spectrum stripping coefficient based on a cross spectrum section:

1) stripping coefficient of thorium element to each characteristic spectrum section of thorium elementThe stripping coefficients of 1 and uranium-radium elements to each characteristic spectrum segment of the uranium-radium elementsAll are the stripping coefficients of 1, potassium element to each characteristic spectrum sectionAre all 1;

2) using a natural gamma radioactive background standard model with a nominal content of Q_ThStandard model of natural gamma-ray radioactive thorium element and nominal content of Q_UThe standard model of natural gamma radioactive uranium element is used for solving the stripping coefficient of i characteristic spectrum bands of the uranium-radium element to the thorium element:

3) using a natural gamma radioactive background standard model with a nominal content of Q_ThStandard model of natural gamma-ray radioactive thorium element and nominal content of Q_KThe natural gamma radioactive potassium element standard model is used for solving the stripping coefficient of the potassium element to i characteristic spectrum bands of the thorium element:

4) using a natural gamma radioactive background standard model with a nominal content of Q_UStandard model of natural gamma-ray radioactive uranium element and nominal content of Q_ThThe natural gamma radioactive thorium element standard model is used for solving the stripping coefficient of the thorium element to j characteristic spectrum bands of the uranium-radium element:

5) using a natural gamma radioactive background standard model with a nominal content of Q_UStandard model of natural gamma-ray radioactive uranium-radium element and nominal content of Q_KThe standard model of natural gamma radioactive potassium element is used for solving the stripping coefficient of j characteristic spectrum segments of uranium-radium element by potassium element:

6) using a natural gamma radioactive background standard model with a nominal content of Q_KStandard model of natural gamma radioactive potassium element and nominal content Q_ThThe natural gamma radioactive thorium element standard model is used for solving the stripping coefficient of the thorium element to k characteristic spectral bands of the potassium element:

7) using a natural gamma radioactive background standard model with a nominal content of Q_KStandard model of natural gamma radioactive potassium element and nominal content Q_UThe standard model of natural gamma radioactive uranium-radium element is used for solving the stripping coefficient of the uranium-radium element to k characteristic spectrum bands of the potassium element:

8) and (4) integrating the steps 1) to 7) in the step (3) to obtain a natural gamma energy spectrum stripping coefficient based on the cross spectrum:

can be formulated as:

wherein x and y represent any natural gamma radioactive element, x/y represents element x to element y, m represents each characteristic spectrum segment, m ═ i + j + k, and m ∈ y.

Technical Field

The invention belongs to the field of nuclear radiation detection, and the method can realize the radioactive element quantification through rapid natural gamma-ray spectral logging in the uranium ore exploration industry, and is particularly suitable for uranium-thorium mixed type or uranium-thorium-potassium mixed type minerals.

Background

Natural gamma-ray logging is a common geophysical method for drilling wells and is also the basic method for uranium exploration. It is prepared by detecting natural decay series (uranium series, thorium series, actinium uranium series, etc.) and potassium (⁴⁰K) The total amount of gamma rays or spectral count rate (both of which are proportional to the decay rate) to estimate the content of uranium, thorium or potassium elements in the formation rock that are characterized by the starting nuclide. The natural gamma logging is to place a gamma total amount logging instrument or a gamma energy spectrum logging instrument into a borehole, measure the natural gamma irradiation rate of rock ore on the borehole wall, and determine the position and the thickness of a radioactive stratum penetrated by the borehole and the content of radioactive elements (uranium, thorium and potassium) according to a gamma irradiation rate curve along the depth of the borehole. At present, gamma logging is a main method for reserve calculation in the exploration of uranium deposits and uranium-thorium mixed deposits, and especially when the core sampling rate in a drill hole is not high, gamma logging based on quantitative radioactive elements is particularly important. The gamma logging standard of China only requires the adoption of a natural gamma total logging method with mature technologyAs the main basis for the quantification of uranium in the formation rock.

In the uranium system and the thorium system in nature, in a radioactive equilibrium state, the proportional relation of the atomic numbers of nuclides in the system is determined, so the relative intensities of gamma rays with different energies are also determined, and uranium and thorium can be identified by selecting the energy of gamma rays of a characteristic nuclide of a certain nuclide from the two systems. The energy of gamma rays emitted by a characteristic nuclide, called characteristic energy, is used in natural gamma-ray spectral logging, e.g. in the uranium family²¹⁴The gamma rays of 1.76MeV emitted by Bi identify uranium, optionally in the thorium series²⁰⁸Tl emits a gamma ray of 2.62MeV to identify thorium and a gamma ray of 1.46MeV to identify potassium. If the gamma rays are counted separately according to the selected characteristic energy, the spectrum is measured. The energy of the gamma rays emitted by the particles is plotted in a coordinate system, the abscissa represents the energy of the gamma rays, and the ordinate represents the corresponding intensity of the gamma rays with the energy, so that a relation graph of the energy and the intensity of the gamma rays is obtained, and the graph is called an energy spectrum graph or an energy spectrum curve graph of natural gamma rays. Therefore, the measured natural gamma energy spectrum is converted into the content of uranium, thorium and potassium in the stratum and is output in the form of a continuous logging curve, and thus the natural gamma energy spectrum logging is carried out.

Compared with natural gamma total amount logging, the natural gamma energy spectrum logging can not only realize the function of total amount logging, but also obtain more useful information and determine the content of uranium, thorium and potassium in the stratum so as to divide the stratum in more detail and research various geological problems related to the distribution of radioactive elements.

Compared with natural gamma total quantity logging, the relative counting rate (uranium, thorium and potassium counting rates) of natural gamma energy spectrum logging is low, the radioactive statistics fluctuation error is large, in order to improve the curve quality, the volume of a gamma ray detector (crystal) must be increased, the speed measurement is reduced, and the method often conflicts with the actual production requirement. And the content of uranium, thorium and potassium in the stratum is different, so that the quality of uranium, thorium and potassium curves is different. The quality of a natural gamma-ray spectrum logging curve not only depends on the performance and the technical level of the logging instrument, but also is influenced by factors such as the logging environment (a borehole and a stratum), the speed measurement, the sampling interval and the like.

At present, a new fast natural gamma energy spectrum logging method in the uranium mine field is urgently needed to be researched, the interpretation precision of the content of radioactive elements can be ensured, the logging speed of the natural gamma energy spectrum can reach the level equivalent to that of natural gamma total logging, and the production and application requirements can be met. The natural gamma-ray energy spectrum logging method based on the cross-spectral method is expected to solve the problem, and the quantitative uranium ore stripping coefficient calculation method based on the energy spectrum logging cross-spectral method is the key for realizing the rapid natural gamma-ray energy spectrum logging method. So far, no report that the method is directly applied to uranium ore natural energy spectrum logging is seen.

Disclosure of Invention

The invention aims to provide a uranium ore quantitative stripping coefficient calculation method based on energy spectrum logging cross spectral bands, which aims to realize radioactive element quantification through rapid natural gamma energy spectrum logging in the uranium ore exploration industry.

The purpose of the invention is realized by the following technical scheme:

(1) according to the positions of the characteristic peaks of different radioactive elements, a natural gamma energy spectrum curve is divided into a plurality of mutually crossed characteristic spectrum sections:

1) selecting i characteristic peaks of thorium, dividing into corresponding i thorium characteristic spectrum sections, wherein the energy range of gamma ray of each characteristic spectrum section is from 400keV to the corresponding characteristic peak, and at least one characteristic spectrum section should contain thorium characteristic peak with energy of 2.62MeV from 400keV,

2) selecting j characteristic peaks of a uranium-radium system, dividing the characteristic peaks into corresponding j characteristic spectrum sections of the uranium-radium system, wherein the energy range of gamma rays of each characteristic spectrum section is from 400keV to the corresponding characteristic peak, at least one characteristic spectrum section comprises the characteristic peaks of the uranium-radium system with the energy of 400keV to 1.76MeV,

3) selecting k characteristic peaks of a potassium system, dividing the k characteristic peaks into corresponding k potassium system characteristic spectrum segments, wherein the gamma ray energy range of each characteristic spectrum segment is from 400keV to the corresponding characteristic peak, and at least one characteristic spectrum segment comprises the potassium system characteristic peak with the energy of 400keV to 1.46 MeV;

(2) calculating the counting rate of each characteristic spectrum segment of thorium series, uranium-radium series and potassium series on a natural gamma radioactive standard model:

1) calculating the counting rate of thorium characteristic spectrum on a natural gamma radioactive background standard modelCounting rate of characteristic spectrum section of uranium-radium systemCounting rate of characteristic spectrum band of potassium series

2) At a nominal content of Q_ThThe counting rate of each characteristic spectrum section corresponding to the thorium element is calculated on a natural gamma radioactive thorium element standard model

At a nominal content of Q_ThThe counting rate of each characteristic spectrum section corresponding to the uranium-radium element is calculated on a natural gamma radioactive thorium element standard model

At a nominal content of Q_ThThe counting rate of each characteristic spectrum section corresponding to the potassium element is obtained on the natural gamma radioactive thorium element standard model

3) At a nominal content of Q_UThe counting rate of each characteristic spectrum section corresponding to the thorium element is calculated on the natural gamma radioactive uranium element standard model

At a nominal content of Q_UThe counting rate of each characteristic spectrum section corresponding to the uranium-radium element is solved on the natural gamma radioactive uranium element standard model

At a nominal content of Q_UThe counting rate of each characteristic spectrum section corresponding to the potassium element is obtained on the natural gamma radioactive uranium element standard model

4) At a nominal content of Q_KThe counting rate of each characteristic spectrum section corresponding to the thorium element is calculated on a natural gamma radioactive potassium element standard model

At a nominal content of Q_KThe counting rate of each characteristic spectrum section corresponding to the uranium-radium element is solved on a natural gamma radioactive potassium element standard model

At a nominal content of Q_KThe counting rate of each characteristic spectrum section corresponding to the potassium element is obtained on the natural gamma radioactive potassium element standard model

(3) And (3) solving a natural gamma energy spectrum stripping coefficient based on a cross spectrum section:

1) stripping coefficient of thorium element to each characteristic spectrum section of thorium elementThe stripping coefficients of 1 and uranium-radium elements to each characteristic spectrum segment of the uranium-radium elementsAll are the stripping coefficients of 1, potassium element to each characteristic spectrum sectionAre all 1;

2) using a natural gamma radioactive background standard model with a nominal content of Q_ThStandard model of natural gamma-ray radioactive thorium element and nominal content of Q_UThe standard model of natural gamma radioactive uranium element is used for solving the stripping coefficient of i characteristic spectrum bands of the uranium-radium element to the thorium element:

3) using a natural gamma radioactive background standard model with a nominal content of Q_ThStandard model of natural gamma-ray radioactive thorium element and nominal content of Q_KThe natural gamma radioactive potassium element standard model is used for solving the stripping coefficient of the potassium element to i characteristic spectrum bands of the thorium element:

4) using a natural gamma radioactive background standard model with a nominal content of Q_UStandard model of natural gamma-ray radioactive uranium element and nominal content of Q_ThThe natural gamma radioactive thorium element standard model is used for solving the stripping coefficient of the thorium element to j characteristic spectrum bands of the uranium-radium element:

5) using a natural gamma radioactive background standard model with a nominal content of Q_UStandard model of natural gamma-ray radioactive uranium-radium element and nominal content of Q_KThe standard model of natural gamma radioactive potassium element is used for solving the stripping coefficient of j characteristic spectrum segments of uranium-radium element by potassium element:

6) by usingStandard model of natural gamma radioactive background with nominal content of Q_KStandard model of natural gamma radioactive potassium element and nominal content Q_ThThe natural gamma radioactive thorium element standard model is used for solving the stripping coefficient of the thorium element to k characteristic spectral bands of the potassium element:

7) using a natural gamma radioactive background standard model with a nominal content of Q_KStandard model of natural gamma radioactive potassium element and nominal content Q_UThe standard model of natural gamma radioactive uranium-radium element is used for solving the stripping coefficient of the uranium-radium element to k characteristic spectrum bands of the potassium element:

8) and (4) integrating the steps 1) to 7) in the step (3) to obtain a natural gamma energy spectrum stripping coefficient based on the cross spectrum:

can be formulated as:

wherein x and y represent any natural gamma radioactive element, x/y represents element x to element y, m represents each characteristic spectrum segment, m ═ i + j + k, and m ∈ y.

The invention has the advantages that: by utilizing a natural gamma-ray spectroscopy well logging stripping coefficient solving method based on a cross-spectral method, the influence of other natural gamma-ray radioactive elements can be stripped in the process of analyzing the content of a certain radioactive element, and the accurate quantification of radioactive elements such as thorium, uranium-radium, potassium and the like is realized; meanwhile, due to the adoption of a cross-spectral method, the measurement count rate of the natural gamma energy spectrum curve is effectively utilized, the signal-to-noise ratio of the natural gamma energy spectrum curve is relatively improved, and the measurement speed of the natural gamma energy spectrum can be further improved. If the method is applied to the natural gamma logging process of the uranium ores, the interpretation precision of the content of the radioactive elements can be ensured, and meanwhile, the logging speed of the natural gamma energy spectrum can reach the same level as that of the natural gamma total logging, so that the production application requirements are met.

Drawings

FIG. 1 is a flowchart of the peel coefficient calculation in example 1 of the present invention;

FIG. 2 is an example of a cross-spectral segmentation method for natural gamma-ray spectral curves containing thorium, uranium-radium and potassium radioactive elements in example 1 of the present invention;

fig. 3 is a schematic diagram of a process for quantifying thorium, uranium-radium and potassium radioactive elements in uranium ore logging in example 1 of the present invention;

FIG. 4 is a graph comparing the interpretation of the uranium-radium content at different logging speeds in the same borehole for example 1 according to the present invention;

FIG. 5 is a graph illustrating the comparison of the interpretation of the uranium-radium content between the natural gamma total amount logging and the natural gamma spectroscopy logging in the model well with the uranium content of 800ppm in example 1 of the present invention.

In the figure: 1-natural gamma-ray spectrum logging curve, 2-dividing the intercrossed characteristic spectrum sections of thorium, uranium, radium and potassium, 3-selecting a background model and thorium, uranium and potassium models with known contents, 4-natural gamma-ray spectrum curve data measured by each model, 5-counting rate of each cross spectrum section and 6-stripping coefficient.

Detailed Description

The invention is described in more detail below with reference to the figures and the detailed description.

The method is characterized in that characteristic peaks corresponding to thorium, uranium-radium and potassium elements in a natural gamma energy spectrum curve are taken as objects, the natural gamma energy spectrum curve is divided into a plurality of mutually crossed characteristic spectrum sections, the counting rates of different elements with unit content in a certain characteristic spectrum section are obtained, and the ratio of the counting rates of the two elements in the characteristic spectrum section is the stripping coefficient.

The invention discloses a uranium ore quantitative stripping coefficient calculation method based on an energy spectrum logging cross spectrum section, which comprises the following steps of:

(1) thorium, uranium-radium, and potassium contain not many gamma nuclides, but they emit characteristic gamma rays of hundreds of energies. The characteristic gamma rays with higher radiation probability and higher energy and the corresponding gamma nuclides are shown in table 1. The existing natural gamma-ray spectral logging can only distinguish a few dozen kinds of characteristic gamma-rays, namely the characteristic gamma-rays with the radiation probability of more than 0.01, the energy of more than 0.4MeV and no overlapping peaks. These characteristic gamma rays are called characteristic peaks on the energy spectrum curve, as shown in fig. 2. According to the positions of the characteristic peaks of different radioactive elements, a natural gamma energy spectrum curve is divided into a plurality of mutually crossed characteristic spectrum sections:

1) selecting i characteristic peaks of thorium, dividing into corresponding i thorium characteristic spectrum sections, wherein the energy range of gamma ray of each characteristic spectrum section is from 400keV to the corresponding characteristic peak, and at least one characteristic spectrum section should contain thorium characteristic peak with energy of 2.62MeV from 400keV,

2) selecting j characteristic peaks of a uranium-radium system, dividing the characteristic peaks into corresponding j characteristic spectrum sections of the uranium-radium system, wherein the energy range of gamma rays of each characteristic spectrum section is from 400keV to the corresponding characteristic peak, at least one characteristic spectrum section comprises the characteristic peaks of the uranium-radium system with the energy of 400keV to 1.76MeV,

3) selecting k characteristic peaks of a potassium system, dividing the k characteristic peaks into corresponding k potassium system characteristic spectrum segments, wherein the gamma ray energy range of each characteristic spectrum segment is from 400keV to the corresponding characteristic peak, and at least one characteristic spectrum segment comprises the potassium system characteristic peak with the energy of 400keV to 1.46 MeV;

(2) calculating the counting rate of each characteristic spectrum segment of thorium series, uranium-radium series and potassium series on a natural gamma radioactive standard model:

1) calculating the counting rate of thorium characteristic spectrum on a natural gamma radioactive background standard modelCounting rate of characteristic spectrum section of uranium-radium systemCounting rate of characteristic spectrum band of potassium series

2) At a nominal content of Q_ThThe counting rate of each characteristic spectrum section corresponding to the thorium element is calculated on a natural gamma radioactive thorium element standard model

At a nominal content of Q_ThThe counting rate of each characteristic spectrum section corresponding to the uranium-radium element is calculated on a natural gamma radioactive thorium element standard model

At a nominal content of Q_ThThe counting rate of each characteristic spectrum section corresponding to the potassium element is obtained on the natural gamma radioactive thorium element standard model

3) At a nominal content of Q_UThe counting rate of each characteristic spectrum section corresponding to the thorium element is calculated on the natural gamma radioactive uranium element standard model

At a nominal content of Q_UThe counting rate of each characteristic spectrum section corresponding to the uranium-radium element is solved on the natural gamma radioactive uranium element standard model

At a nominal content of Q_UThe counting rate of each characteristic spectrum section corresponding to the potassium element is obtained on the natural gamma radioactive uranium element standard model

4) At a nominal content of Q_KThe counting rate of each characteristic spectrum section corresponding to the thorium element is calculated on a natural gamma radioactive potassium element standard model

At a nominal content of Q_KThe counting rate of each characteristic spectrum section corresponding to the uranium-radium element is solved on a natural gamma radioactive potassium element standard model

At a nominal content of Q_KThe counting rate of each characteristic spectrum section corresponding to the potassium element is obtained on the natural gamma radioactive potassium element standard model

(3) And (3) solving a natural gamma energy spectrum stripping coefficient based on a cross spectrum section:

1) stripping coefficient of thorium element to each characteristic spectrum section of thorium elementThe stripping coefficients of 1 and uranium-radium elements to each characteristic spectrum segment of the uranium-radium elementsAll are the stripping coefficients of 1, potassium element to each characteristic spectrum sectionAre all 1;

2) using a natural gamma radioactive background standard model with a nominal content of Q_ThStandard model of natural gamma-ray radioactive thorium element and nominal content of Q_UThe standard model of natural gamma radioactive uranium element is used for solving the stripping coefficient of i characteristic spectrum bands of the uranium-radium element to the thorium element:

3) using a natural gamma radioactive background standard model with a nominal content of Q_ThStandard model of natural gamma-ray radioactive thorium element and nominal content of Q_KThe natural gamma radioactive potassium element standard model is used for solving the stripping coefficient of the potassium element to i characteristic spectrum bands of the thorium element:

4) using a natural gamma radioactive background standard model with a nominal content of Q_UStandard model of natural gamma-ray radioactive uranium element and nominal content of Q_ThThe natural gamma radioactive thorium element standard model is used for solving the stripping coefficient of the thorium element to j characteristic spectrum bands of the uranium-radium element:

5) using a natural gamma radioactive background standard model with a nominal content of Q_UStandard model of natural gamma-ray radioactive uranium-radium element and nominal content of Q_KThe standard model of natural gamma radioactive potassium element is used for solving the stripping coefficient of j characteristic spectrum segments of uranium-radium element by potassium element:

6) using a natural gamma radioactive background standard model with a nominal content of Q_KStandard model of natural gamma radioactive potassium element and nominal content Q_ThThe natural gamma radioactive thorium element standard model is used for solving the stripping coefficient of the thorium element to k characteristic spectral bands of the potassium element:

7) using a natural gamma radioactive background standard model with a nominal content of Q_KStandard model of natural gamma radioactive potassium element and nominal content Q_UThe standard model of natural gamma radioactive uranium-radium element is used for solving the stripping coefficient of the uranium-radium element to k characteristic spectrum bands of the potassium element:

8) and (4) integrating the steps 1) to 7) in the step (3) to obtain a natural gamma energy spectrum stripping coefficient based on the cross spectrum:

can be formulated as:

wherein x and y represent any natural gamma radioactive element, x/y represents element x to element y, m represents each characteristic spectrum segment, m ═ i + j + k, and m ∈ y.

(4) Calculating a natural gamma energy spectrum conversion coefficient based on a cross spectrum segment:

1) using a natural gamma radioactive background standard model and a nominal content of Q_ThThe natural gamma radioactive thorium element standard model calculates the conversion coefficient of the thorium element corresponding to each characteristic spectrum:

2) using a natural gamma radioactive background standard model and a nominal content of Q_UThe standard model of natural gamma radioactive uranium-radium element is used for solving the conversion coefficient of the uranium-radium element corresponding to each characteristic spectrum:

3) utilizing natural gamma radioactive background standard model and nominal contentIs Q_KThe standard model of natural gamma radioactive potassium element is used for solving the conversion coefficient of potassium element corresponding to each characteristic spectrum:

and (4) integrating the steps 1) to 3) in the step (4) to obtain a natural gamma energy spectrum conversion coefficient based on the cross spectrum:

can be formulated as:

wherein y represents an arbitrary natural gamma radioactive element, Q_yAnd (3) expressing the nominal content of the radioactive standard model element y, wherein m represents each characteristic spectrum segment, and m belongs to i + j + k and m belongs to y.

(5) The content q of the radioactive element is obtained according to the following formula_x：

Can be formulated as:

wherein x and y represent any natural gamma radioactive elements (thorium, uranium-radium and potassium, respectively), and x/y represents element x to element y, q_xRepresenting different contents of radioactive elements, m representing each characteristic spectrum, m ═ i + j + k, m ∈ y.

If i, j and k are all 1, one characteristic spectrum segment is selected for thorium element, uranium-radium element and potassium element, natural gamma-ray spectrum logging is completed by the process shown in fig. 3 of the embodiment 1, the content of radioactive elements of thorium, uranium-radium and potassium is obtained, the content comparison of explanation of the radioactive elements of uranium-radium is obtained under the condition of different logging speeds in the same well hole, and the effect is shown in fig. 4. And natural gamma total amount logging and natural gamma energy spectrum logging based on a cross-spectral method are respectively carried out in the model well, so that the content of radioactive elements such as thorium, uranium-radium and potassium in the total amount logging interpretation result and the energy spectrum logging interpretation result are compared, and the effect is shown in fig. 5. As can be seen from the comparison effect of the images in FIGS. 4 and 5, by utilizing the natural gamma-ray spectrum logging stripping coefficient calculation method based on the cross-spectral method, when the logging speed of the natural gamma-ray spectrum reaches 6m/min, the accurate quantification of radioactive elements such as thorium, uranium-radium, potassium and the like can be still realized, and the production and application requirements are met.

TABLE 1 Gamma-nuclide data sheet for Natural radioactive decay (only characteristic Gamma-rays with high radiation probability and energy are listed)

Note: data are presented for characteristic gamma rays and their gamma nuclides for only radiation probability >0.001 (meaning the radiation probability of a single radioactive decay), thorium, uranium-radium, and potassium emissions with energy >0.4 MeV.