CN115166844A - Combined gamma energy spectrum logging system and gamma energy spectrum logging method - Google Patents
Combined gamma energy spectrum logging system and gamma energy spectrum logging method Download PDFInfo
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- 238000001228 spectrum Methods 0.000 title claims abstract description 69
- 238000000034 method Methods 0.000 title claims abstract description 40
- 239000000523 sample Substances 0.000 claims abstract description 87
- 238000001514 detection method Methods 0.000 claims abstract description 43
- 238000005259 measurement Methods 0.000 claims abstract description 20
- 239000002131 composite material Substances 0.000 claims abstract description 7
- 229910052770 Uranium Inorganic materials 0.000 claims description 63
- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical compound [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 claims description 63
- ZSLUVFAKFWKJRC-IGMARMGPSA-N 232Th Chemical compound [232Th] ZSLUVFAKFWKJRC-IGMARMGPSA-N 0.000 claims description 48
- 229910052776 Thorium Inorganic materials 0.000 claims description 48
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 34
- 229910052700 potassium Inorganic materials 0.000 claims description 34
- 239000011591 potassium Substances 0.000 claims description 34
- 239000011159 matrix material Substances 0.000 claims description 25
- 230000035945 sensitivity Effects 0.000 claims description 22
- 239000013078 crystal Substances 0.000 claims description 16
- MOOUSOJAOQPDEH-UHFFFAOYSA-K cerium(iii) bromide Chemical compound [Br-].[Br-].[Br-].[Ce+3] MOOUSOJAOQPDEH-UHFFFAOYSA-K 0.000 claims description 12
- 238000001730 gamma-ray spectroscopy Methods 0.000 claims description 10
- 238000000084 gamma-ray spectrum Methods 0.000 claims description 8
- 239000000203 mixture Substances 0.000 claims description 6
- 230000005251 gamma ray Effects 0.000 claims description 5
- 230000015572 biosynthetic process Effects 0.000 claims description 3
- GNFTZDOKVXKIBK-UHFFFAOYSA-N 3-(2-methoxyethoxy)benzohydrazide Chemical compound COCCOC1=CC=CC(C(=O)NN)=C1 GNFTZDOKVXKIBK-UHFFFAOYSA-N 0.000 claims description 2
- 238000004364 calculation method Methods 0.000 abstract description 9
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- 238000010586 diagram Methods 0.000 description 3
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- 238000005070 sampling Methods 0.000 description 3
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- 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
- G01V5/14—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 a combination of several sources, e.g. a neutron and a gamma source
Abstract
The invention relates to a combined gamma energy spectrum logging system and a gamma energy spectrum logging method, wherein the combined gamma energy spectrum logging system comprises a winch, a cable is wound on the winch, a combined gamma energy spectrum probe and a control host are respectively connected at two ends of the cable, the control host is in signal connection with a main shaft encoder on the winch, and the control host is connected with a computer; the composite gamma energy spectrum probe tube comprises a probe tube shell, wherein a probe tube internal controller, a power supply unit, a memory and two groups of detection devices are arranged in the probe tube shell, and the two groups of detection devices are positioned at the lower end of the probe tube shell and are arranged along the length direction of the probe tube shell. According to the method, the content values obtained by performing spectrum-resolving calculation on each group of detection devices are superposed into the logging curve according to the depth information, and the data acquired by each group of detectors are utilized, so that the measurement precision and efficiency are improved, and the method is particularly suitable for logging of the uranium-thorium mixed deposit.
Description
Technical Field
The invention relates to a gamma energy spectrum logging technology, in particular to a combined gamma energy spectrum logging system instrument and a gamma energy spectrum logging method.
Background
Uranium resources are important strategic resources and occupy an important position in national defense modernization construction and economic construction in China. The method has the advantages that high requirements are provided for uranium resource storage, the exploration capacity of uranium ores in China must be improved, uranium resource storage increase is realized, and efficient uranium resource exploration and reserve evaluation technology and method research is developed.
At present, the main logging method for calculating uranium ore reserves is a gamma total logging method, and the method is to calculate the equivalent content of uranium by taking the contributions of gamma radionuclides such as uranium, thorium and potassium in a stratum as the contributions of uranium.
For the uranium ores capable of being leached into sandstone generally without thorium, gamma total logging can be adopted to determine the uranium content. But for the hard rock uranium deposit, part of the hard rock uranium deposit belongs to uranium-thorium mixed deposit.
For a uranium-thorium mixed deposit, a gamma total logging method cannot distinguish the proportion of uranium-thorium nuclides in a stratum and cannot meet the requirement of accurately measuring the content of uranium and thorium in a uranium ore drilling stratum.
Meanwhile, on the uranium-thorium mixed ore bed, the uranium content used for calculating reserves is obtained by correcting a gamma total logging result through analysis and test after collecting rock cores. The core sampling and analysis test work not only wastes time and labor, reduces the working efficiency, but also costs a large amount of expenses and improves the production time cost.
Disclosure of Invention
The invention aims to provide a combined gamma energy spectrum logging system and a gamma energy spectrum logging method, so as to solve the problems of low measurement precision, low efficiency and high cost of the conventional uranium-thorium mixed deposit.
The invention is realized in the following way: a combined gamma-ray spectrum logging system comprises a winch, wherein a cable is wound on the winch, the tail end of the cable is connected with a combined gamma-ray spectrum probe, the head end of the cable is connected with a control host, a spindle encoder is arranged on a rotating shaft of the winch, the control host is in signal connection with the spindle encoder, and the control host is connected with a computer; the combined gamma energy spectrum probe comprises a probe shell, wherein an internal probe controller, a power supply unit, a memory and two groups of detection devices are arranged in the probe shell, the two groups of detection devices are positioned at the lower end of the probe shell and are arranged in sequence along the length direction of the probe shell, and each detection device comprises a multichannel analyzer and a detector.
The detector comprises a high-voltage power supply, a voltage division circuit, a cerium bromide crystal and a photomultiplier.
The invention also discloses a gamma energy spectrum logging method, which is realized based on the combined gamma energy spectrum logging system and comprises the following steps.
a. A combined gamma-ray spectrum logging system is arranged on a logging platform on a detection site, a winch is arranged at a logging port, and a combined gamma-ray spectrum probe tube extends into a logging well.
b. And setting the current logging depth, and determining an initial value of the depth of the composite gamma-ray spectrum probe.
c. The computer sends out a measurement starting instruction and sends working parameters of the two detection devices to the control host, wherein the working parameters comprise an energy window range.
d. The control host receives and executes the starting instruction, transmits the working parameters of the two detection devices to the combined gamma energy spectrum probe, starts the winch to drive the combined gamma energy spectrum probe to move, records the depth information sent by the winch and sends the depth information to the combined gamma energy spectrum probe.
e. And after receiving the working parameters and the depth information, the controller in the probe tube respectively sends the working parameters to the two multi-channel analyzers to start data acquisition, and the multi-channel analyzers start to work according to the respective working parameters to acquire the energy spectrum data.
f. The two multi-channel analyzers respectively send the acquired energy spectrum data to the controller in the probe tube, respectively calculate and store energy window data, simultaneously inquire and store corresponding depth information, and then pack and send the data to the control host.
g. And the control host sends the data packet to a computer after receiving the data packet sent by the probe, and the computer respectively analyzes the energy window data of the two detection devices and calculates the contents of potassium, uranium and thorium according to an inverse matrix spectrum resolving method.
h. And overlapping the contents of potassium, uranium and thorium obtained by the two detection devices to a logging curve according to depth information.
In step c, the energy window range is:
thorium A, the energy window range is 845-1000 keV; uranium A, energy window range 1060-1330 keV; potassium, energy window range 1370-1570 keV; uranium with an energy window range of 1660-1860 keV; thorium with an energy window ranging from 2400 keV to 2800keV; and, for the total channel, the energy window range is 400-3000 keV.
In step g, 13 model sources of F-0-I, KF-6-I, UF-0.2-I, thF-0.7-I, UThF-0.01-0.03-I, UThF-0.2-0.07-I, UThF-0.07-0.2-I, UF-0.03-I, UF-0.5-I, UF-1.0-I, thF-1.5-I, thF-0.3-I and ThF-0.05-I are selected, two detectors are respectively measured, ten sets of data are measured for each model source, the measurement time for each set is 60 seconds, and a sensitivity coefficient matrix and uranium, thorium and potassium content values are calculated in sequence according to the measured data.
Calculating a sensitivity coefficient matrix by using measurement data of a uranium model source UF-0.2-I, a thorium model source ThF-0.3-I, a potassium model source KF-6-I and a background model source F-0-I according to the following formula, wherein the background model source is used for deducting corresponding background counting rate and content;
establishing a linear equation system:
in the formula:
i-the serial number of the energy window;
j is the serial number of uranium, thorium and potassium elements;
n i net count rate after background subtraction by ith energy window, s -1 ；
s ij Sensitivity coefficient of gamma ray emitted by jth element in unit content to ith energy window, 1/(s × 10) for uranium and thorium elements -6 ) For potassium element, 1/(s times 10) -2 )；
q j Content of jth element,. Times.10 -6 g/g (uranium) × 10 -6 g/g (thorium) and x 10 -2 g/g (potassium);
the matrix expression of the above formula is:
S·Q＝N
in the formula:
s-sensitivity coefficient matrix, from S ij Of composition [ 5X 3]A matrix;
q-formula of uranium, thorium and potassium content in the formation, i.e. from Q j A 3-element formula;
n-column of counting rates per energy window, from N i 5-element formula of the composition.
According to the energy window data of the two detection devices and the obtained sensitivity coefficient matrix, according to a formula Q = S -1 N calculates the uranium, thorium and potassium content values.
At present, the diameter of a common uranium ore drill hole is 60mm, and the diameter of the drill hole is smaller, so that the diameter of a cerium bromide crystal cannot be too large; in order to reduce the influence of pulse accumulation and not influence the measurement of a thin ore layer, the crystal length is not too long; in gamma logging, the acquisition time of the probe is short, and is generally 1 second. Under these constraints, it is desirable to improve the sensitivity and accuracy of the probe based on a small volume probe.
The combined gamma-energy spectrum logging system is provided with a combined gamma-energy spectrum probe, wherein the combined gamma-energy spectrum probe comprises two groups of detection devices, the two groups of detection devices are sequentially arranged along the length direction of a probe shell, the arrangement mode of the two groups of detection devices can enable the volume of cerium bromide crystals to be as large as possible, the size of the cerium bromide crystals is 38 × 38mm, the diameter of the probe is not influenced, and therefore the miniaturization of the detection devices is achieved. Array detector about two sets of detecting device constitution, for single detector, can improve the holistic sampling rate of instrument, improve precision and sensitivity, under the circumstances of guaranteeing equal precision, can reduce measuring time, improve logging speed, double improvement production efficiency, can reduce dead time effect simultaneously, improve measuring range.
The gamma energy spectrum logging method uses a combined gamma energy spectrum logging system, simultaneously determines the energy range of six energy windows, increases two energy windows of thorium A and uranium A, utilizes more intermediate energy regions with higher counting rates and effectively improves the sensitivity. When the traditional energy window range is used, because the detection efficiency of the small-size crystal is low, a long time is needed to obtain an obvious characteristic peak, if the measurement accuracy reaches 5%, the time is more than 20 seconds, and the logging working efficiency is seriously reduced. Under the condition of achieving the same precision, by adopting the six-energy-window energy range, the logging time is greatly shortened, and the logging efficiency is greatly improved.
The method simultaneously uses an inverse matrix spectrum resolving method to resolve the full spectrum data, more utilizes the gamma spectrum full spectrum data information, and improves the content sensitivity of the uranium window and the thorium window. Each group of detectors of the invention work independently at the same time, the respective collected gamma data is given according to the working parameters of the detectors, and the detectors of each group are calibrated to obtain independent calculation parameters, so that the error of each group of detectors is ensured to be the lowest, rather than simple accumulation calculation. And the final content value obtained by performing spectrum resolution calculation on each group of detectors is superposed to a logging curve according to depth information, and data acquired by each group of detectors is utilized, so that the measurement precision and efficiency are improved.
The method can improve the logging measurement precision, the logging speed and the production efficiency, and is particularly suitable for logging of the uranium-thorium mixed deposit.
Drawings
FIG. 1 is a schematic diagram of a composite gamma-ray spectroscopy logging system of the present invention.
Fig. 2 is a structural diagram of the composite gamma spectrum probe of the invention.
Fig. 3 is a diagram of the communication protocol architecture of the present invention.
Detailed Description
As shown in fig. 1, the combined gamma-ray spectroscopy well logging system of the present invention includes a winch, a cable is wound on the winch, the cable includes a signal and a signal for transmitting electric energy, a combined gamma-ray spectroscopy probe is connected to the end of the cable, a control host is connected to the head end of the cable, a spindle encoder (optical pulse generator) is disposed on a rotating shaft of the winch, the cable is unwound or wound by the drive of the winch, the control host is in signal connection with the spindle encoder, the control host is connected to a computer, the unwinding length of the cable can be calculated by the signal of the spindle encoder, and the computer is a carrier for acquiring software.
As shown in fig. 2, the combined gamma spectrum probe comprises a probe shell, wherein a probe internal controller, a power supply unit, a memory and two groups of detection devices are arranged in the probe shell, the two groups of detection devices are positioned at the lower end of the probe shell and are sequentially arranged along the length direction of the probe shell, and each detection device comprises a multichannel analyzer and a detector.
The two detectors are a detector a and a detector B, respectively, and the two multichannel analyzers are a multichannel analyzer a and a multichannel analyzer B, respectively.
The detector comprises a high-voltage power supply, a voltage division circuit, a cerium bromide crystal and a photomultiplier.
In the method, the length of a cable is generally in a range of hundreds of meters in consideration of underground measurement, and the influence of line loss is required to be considered in long-distance power supply, so that high voltage and low current are selected for power supply. The DC-DC module has a wide input power supply range (6V-60V), converts the voltage transmitted by the control host along the cable into +5V and +3.3V, and supplies power to the devices such as a controller, a storage unit, a high-voltage module, a voltage division circuit and a multichannel analyzer in the probe.
Because the data memory in the probe tube needs to store full-spectrum data, the characteristics of high storage speed, large storage capacity, small volume, low power consumption and the like must be met, and the FLASH FLASH memory is adopted. The flash memory has the advantages of high access speed, no noise, small heat dissipation, small size, light weight and the like.
And the inner controller of the probe is in data communication with the multi-channel analyzer A and the multi-channel analyzer B, and the data of the multi-channel analyzer A and the multi-channel analyzer B are packaged and sent to the host machine on the well through the logging cable.
The detector A comprises a high-voltage power supply A, a voltage division circuit A, a cerium bromide crystal A and a photomultiplier A. During measurement, gamma rays enter the cerium bromide crystal A and interact with substances of the cerium bromide crystal A to ionize and excite atoms and molecules in the cerium bromide crystal A, and scintillation light is formed during deexcitation or recombination. The scintillation light is collected by the photocathode of the photomultiplier A, and then the emitted photoelectrons are multiplied and then collected by the anode to output an electric signal. The high-voltage power supply A and the voltage division circuit A provide power supply required by work for the photomultiplier A.
The multichannel analyzer A is connected with the detector A and mainly responsible for amplifying signals, shaping and filtering the signals to enable pulse signals to be close to symmetrical waveforms as much as possible, then an ADC (analog-to-digital converter) circuit in the multichannel analyzer performs analog-to-digital conversion on electric pulses output by the detector to generate energy spectrum curve data, and meanwhile, the multichannel analyzer A is also responsible for spectral line accumulation, communication processing, execution of instructions of a controller in the probe, control of a high-voltage power supply and the like.
The structure and function of the detector A and the multi-channel analyzer B are the same as those of the detector A and the multi-channel analyzer A.
Two groups of detection devices are used for enabling the detection range of the uranium content to reach (100 multiplied by 10) -6 ～1.0×10 -2 ) g/g, the detection range of the thorium content reaches (100 multiplied by 10) -6 ～1.5×10 -2 )g/g。
As shown in FIG. 3, the computer of the present invention communicates with the control host computer by USB, and the control host computer communicates with the controller inside the probe tube by RS-485; and the communication between the detector internal controller and the two multichannel analyzers adopts SPI communication.
Two sets of detection devices are arranged in the probe tube shell in sequence along the length direction of the probe tube shell, and the arrangement mode of the two sets of detection devices can enable the volume of each cerium bromide crystal to be as large as possible, and does not influence the diameter of the probe tube, so that the miniaturization of the detection devices is realized. The probe has a smaller diameter (less than or equal to 53 mm) and can enter a well with a smaller bore.
Array detector about two sets of detecting device constitution, for single detector, can improve the holistic sampling rate of instrument, improve precision and sensitivity, under the circumstances of guaranteeing equal precision, can reduce measuring time, improve logging speed, double improvement production efficiency, can reduce dead time effect simultaneously, improve measuring range.
The invention also discloses a gamma energy spectrum logging method, which is realized based on the combined gamma energy spectrum logging system and comprises the following steps.
1. And (4) arranging equipment.
A combined gamma-ray spectrum logging system is arranged on a logging platform on a detection site, a winch is arranged at a logging port, and a combined gamma-ray spectrum exploring tube extends into a log.
2. And (4) setting the depth.
And setting the current logging depth, sending the logging depth to a control host by the computer, receiving and executing instructions by the control host, and determining the initial value of the depth of the composite gamma-spectrum probe by the control host.
3. The measurement is started.
The computer sends out a measurement starting instruction and sends working parameters of the two detection devices to the control host, wherein the working parameters comprise an energy window range, high voltage and the like.
The control host receives and executes the starting instruction, transmits the working parameters of the two detection devices to the combined gamma energy spectrum probe, starts the winch to drive the combined gamma energy spectrum probe to move, records the depth information sent by the winch and sends the depth information to the combined gamma energy spectrum probe.
And after receiving the working parameters and the depth information, the controller in the probe tube respectively sends the working parameters to the two multi-channel analyzers to start data acquisition, and the multi-channel analyzers start to work according to the respective working parameters to acquire the energy spectrum data.
The working process of energy spectrum data acquisition comprises the following steps:
(1) The gamma rays enter the scintillator to interact with the substance of the scintillator, so that atoms and molecules in the substance of the scintillator are ionized and excited, and scintillation light is formed when the atoms and the molecules are demagnetized or compounded.
(2) After the scintillation light is collected by the photocathode of the multiplier tube, the emitted photoelectrons are multiplied and amplified, and then collected by the anode to output an electric signal.
(3) The multichannel analyzer analyzes the amplitude of the electric signal and performs statistics according to the amplitude of the signal.
4. And (6) data transmission.
The two multi-channel analyzers respectively send the acquired energy spectrum data to the controller in the probe tube, respectively calculate and store energy window data, simultaneously inquire and store corresponding depth information, and then pack and send the data to the control host.
The method comprises the following specific steps:
(1) The internal controller of the probe receives the data from the multi-channel analyzer A, firstly performs CRC validation, if the validation is passed, the CRC validation is stored in a memory, otherwise, the internal controller of the probe requires the multi-channel analyzer A to retransmit the data.
(2) And the internal controller of the probe calculates and stores the energy window data of the probe according to the working parameters of the detector A, and inquires and stores the depth value of the detector A at the moment to the control host.
(3) Then, the internal controller of the probe receives the data from the multi-channel analyzer B, performs CRC validation, if the validation is passed, the CRC validation is stored in the memory, otherwise, the internal controller of the probe requests the multi-channel analyzer B to retransmit the data.
(4) And the controller in the probe calculates and stores energy window data of the probe according to the working parameters of the detector B, and inquires and stores the depth value of the detector B to the control host.
(5) And the internal controller of the probe receives the data of the multi-channel analyzers A and B, packages the data through cables, and sends the data to the control host by utilizing an RS-485 communication protocol.
The packet structure of the multichannel analyzer is shown in table 1.
TABLE 1 packet structure table for multichannel analyzer
And the control host sends the data packet to a computer after receiving the data packet sent by the probe, and the computer analyzes the energy window data of the two detection devices respectively and calculates the contents of potassium, uranium and thorium according to an inverse matrix spectrum resolving method.
The method comprises the following specific steps: and after receiving the data packet sent by the internal controller of the probe, the control host firstly performs CRC (cyclic redundancy check) verification, if the data packet passes the verification, the CRC is stored, and otherwise, the internal controller of the probe is required to retransmit. The control host is responsible for converting a communication protocol and sending a data packet to acquisition software on the computer through a USB protocol. After receiving the data of the probe tube, the acquisition software on the computer firstly performs CRC check, if the data passes the check, the CRC check is stored, otherwise, the host is required to be controlled to retransmit the data. Analyzing the window data of the detector A by acquisition software on the computer, and calculating the contents of potassium, uranium and thorium according to an inverse matrix spectrum resolving method; and analyzing the window data of the detector B, and calculating the contents of potassium, uranium and thorium according to an inverse matrix spectrum resolving method.
The data packet structure of the probe internal controller is shown in table 2.
Table 2 packet structure table of probe tube internal controller
5. And (6) drawing a logging curve.
And overlapping the contents of potassium, uranium and thorium obtained by the two detection devices to a logging curve according to depth information.
And (4) taking the depth value in the data packet as a Y axis, and taking the calculated contents of potassium, uranium and thorium as an X axis to describe a logging curve. At the moment, the energy spectrum data of different depths acquired by the multi-channel analyzers A and B are converted into a unified logging curve, and logging work is completed.
The energy window ranges for the two detection devices are shown in table 3:
the invention adds two energy windows of thorium A and uranium A. Thorium A, the energy window range is 845-1000 keV; uranium A, energy window range 1060-1330 keV; potassium, energy window range 1370-1570 keV; uranium, energy window range 1660-1860 keV; thorium with an energy window ranging from 2400 keV to 2800keV; and, the total channel, the energy window range is 400-3000 keV.
TABLE 3 energy Range of the six energy windows
In the process of spectrum decomposition, 13 model sources of F-0-I, KF-6-I, UF-0.2-I, thF-0.7-I, UThF-0.01-0.03-I, UThF-0.2-0.07-I, UThF-0.07-0.2-I, UF-0.03-I, UF-0.5-I, UF-1.0-I, thF-1.5-I, thF-0.3-I and ThF-0.05-I are selected, two detectors are respectively measured, ten sets of data are measured for each model source, the measuring time of each set is 60 seconds, and a sensitivity coefficient matrix and content values of uranium, thorium and potassium are sequentially calculated according to the measured data.
The logging test data of the detector A are obtained and shown in table 4, the logging test data of the detector B are shown in table 5, the counting rate of the newly added uranium A window is 3.1 times that of the traditional uranium window, the counting rate of the newly added thorium A window is 3.2 times that of the traditional thorium window, and the sensitivity of the instrument can be improved due to the increase of the counting rate of the window.
TABLE 4 Detector A logging test data recording table
TABLE 5 logging test data recording table for detector B
And calculating a sensitivity coefficient matrix by using the measurement data of the uranium model source UF-0.2-I, the thorium model source ThF-0.3-I, the potassium model source KF-6-I and the background model source F-0-I according to the following formula, wherein the background model source is used for deducting the corresponding background counting rate and content.
Establishing a linear equation system:
in the formula:
i is the serial number of the energy window;
j is the serial number of uranium, thorium and potassium elements;
n i net count rate after background subtraction by ith energy window, s -1 ；
s ij Sensitivity coefficient of gamma ray emitted by jth element in unit content to ith energy window, 1/(s × 10) for uranium and thorium elements -6 ) For potassium element, 1/(s times 10) -2 )；
q j Content of jth element,. Times.10 -6 g/g (uranium) × 10 -6 g/g (thorium) and x 10 -2 g/g (potassium).
The matrix expression of the above formula is:
S·Q＝N
in the formula:
s-sensitivity coefficient matrix, from S ij Of composition [ 5X 3]A matrix;
q-formula of uranium, thorium and potassium content in the formation, i.e. from Q j A 3-element formula;
n-line of individual energy window counting rates, from N i A 5-element formula.
The calculated peel coefficient for probe a is shown in table 6 and the peel coefficient for probe B is shown in table 7.
TABLE 6 formula for calculating A stripping coefficient and content of detector
TABLE 7 formula for calculating the stripping coefficient and content of detector B
According to the energy window data of the two detection devices and the obtained sensitivity coefficient matrix, according to the formula Q = S -1 N calculates the uranium, thorium and potassium content values.
The verification model source adopts three mixed model sources of UThF-0.2-0.07-I, UThF-0.07-0.2-I and UThF-0.01-0.03-I. The relative deviations of the uranium and thorium elements measured in the three mixed model sources were calculated according to the above-described solution spectrum calculation method, and the calculation results are shown in tables 8 and 9. From tables 8 and 9, it can be known that the relative deviation of uranium and thorium elements measured in three mixed model sources by using the method is less than 6%, so that the method has better measurement accuracy.
TABLE 8 relative deviation test results for detector A hybrid model
TABLE 9 relative deviation test results for detector B hybrid model
Because the diameter of a current common uranium ore drill hole is 60mm, the diameter of the drill hole is smaller, so that the diameter of a cerium bromide crystal cannot be too large; in order to reduce the influence of pulse accumulation and not influence the measurement of a thin ore layer, the crystal length is not too long; in gamma logging, the acquisition time of the probe is short, and is generally 1 second. Under these constraints, it is necessary to improve the sensitivity and accuracy of the probe tube on the basis of a small-sized probe.
The gamma energy spectrum logging method uses a combined gamma energy spectrum logging system, simultaneously determines the energy range of six energy windows, more utilizes the middle energy region with higher counting rate and effectively improves the sensitivity. When the traditional energy window range is used, because the detection efficiency of the small-size crystal is low, a long time is needed to obtain an obvious characteristic peak, if the measurement accuracy reaches 5%, the time is more than 20 seconds, and the logging working efficiency is seriously reduced. Under the condition of achieving the same precision, by adopting the six-energy-window energy range, the logging time is greatly shortened, and the logging efficiency is greatly improved.
The method simultaneously analyzes the full-spectrum data by using an inverse matrix spectrum-resolving method, more utilizes the information of the gamma-spectrum full-spectrum data, and improves the content sensitivity of the uranium window and the thorium window. Each group of detectors of the invention work independently at the same time, the respective collected gamma data is given according to the working parameters of the detectors, and the detectors of each group are calibrated to obtain independent calculation parameters, so that the error of each group of detectors is ensured to be the lowest, rather than simple accumulation calculation. And the final content value obtained by performing spectrum resolution calculation on each group of detectors is superposed to a logging curve according to depth information, and data acquired by each group of detectors is utilized, so that the measurement precision and efficiency are improved.
The method can improve the logging measurement precision, the logging speed and the production efficiency, and is particularly suitable for logging the uranium-thorium mixed deposit.
Claims (7)
1. The combined gamma-ray energy spectrum logging system is characterized by comprising a winch, wherein a cable is wound on the winch, the tail end of the cable is connected with a combined gamma-ray energy spectrum probe, the head end of the cable is connected with a control host, a spindle encoder is arranged on a rotating shaft of the winch, the control host is in signal connection with the spindle encoder, and the control host is connected with a computer; the combined gamma energy spectrum probe comprises a probe shell, wherein a probe internal controller, a power supply unit, a memory and two groups of detection devices are arranged in the probe shell, the two groups of detection devices are located at the lower end of the probe shell and are arranged in sequence along the length direction of the probe shell, and each detection device comprises a multichannel analyzer and a detector.
2. The composite gamma spectrometry logging system of claim 1, wherein the detector comprises a high voltage power supply, a voltage divider circuit, a cerium bromide crystal, and a photomultiplier tube.
3. A gamma-ray spectroscopy well logging method, which is implemented based on the combined gamma-ray spectroscopy well logging system of claim 1, and comprises the following steps:
a. arranging a combined gamma energy spectrum logging system on a logging platform on a detection site, arranging a winch at a logging port, and extending a combined gamma energy spectrum probe into a logging well;
b. setting the current logging depth, and determining the initial value of the depth of the composite gamma-ray spectrum probe;
c. the computer sends a measurement starting instruction and sends working parameters of the two detection devices to the control host, wherein the working parameters comprise energy window ranges;
d. the control host receives and executes the starting instruction, forwards the working parameters of the two detection devices to the combined gamma energy spectrum probe, starts the winch to drive the combined gamma energy spectrum probe to move, records the depth information sent by the winch and sends the depth information to the combined gamma energy spectrum probe;
e. after receiving the working parameters and the depth information, the controller in the probe tube respectively sends the working parameters to two multi-channel analyzers to start data acquisition, and the multi-channel analyzers start working according to the respective working parameters to acquire energy spectrum data;
f. the two multi-channel analyzers respectively send the acquired energy spectrum data to the controller in the probe tube, respectively calculate and store energy window data, simultaneously inquire and store corresponding depth information, and then pack and send the data to the control host;
g. the control host sends the data packets to a computer after receiving the data packets sent by the probe, the computer respectively analyzes energy window data of the two detection devices, and the contents of potassium, uranium and thorium are calculated according to an inverse matrix spectrum resolving method;
h. and overlapping the contents of potassium, uranium and thorium obtained by the two detection devices to a logging curve according to depth information.
4. A gamma spectrometry logging method according to claim 3, wherein in step c the energy window ranges are:
thorium A, the energy window range is 845-1000 keV; uranium A, energy window range 1060-1330 keV; potassium, energy window range 1370-1570 keV; uranium, energy window range 1660-1860 keV; thorium with an energy window ranging from 2400 keV to 2800keV; and, the total channel, the energy window range is 400-3000 keV.
5. A gamma spectrometry logging method according to claim 3, wherein in step g 13 model bodies of F-0-I, KF-6-I, UF-0.2-I, thF-0.7-I, UThF-0.01-0.03-I, UThF-0.2-0.07-I, UThF-0.07-0.2-I, UF-0.03-I, UF-0.5-I, UF-1.0-I, thF-1.5-I, thF-0.3-I and ThF-0.05-I are selected, two detectors are measured separately, ten sets of data are measured for each model body, each set of data measuring time is 60 seconds, and the sensitivity coefficient matrix and the uranium, thorium and potassium content values are calculated in turn from the measured data.
6. A gamma spectrometry logging method according to claim 5, wherein a sensitivity coefficient matrix is calculated using measured data from uranium model source UF-0.2-I, thorium model source ThF-0.3-I, potassium model source KF-6-I and background model source F-0-I according to the formula, wherein the background model source is used to subtract the corresponding background count rate and content;
establishing a linear equation set:
in the formula:
i-the serial number of the energy window;
j-the serial numbers of uranium, thorium and potassium elements;
n i net count rate after background subtraction by ith energy window, s -1 ；
s ij Sensitivity coefficient of gamma ray emitted by jth element in unit content to ith energy window, 1/(s × 10) for uranium and thorium elements -6 ) For potassium element, 1/(s times 10) -2 )；
q j Content of jth element,. Times.10 -6 g/g (uranium) × 10 -6 g/g (thorium) and x 10 -2 g/g (potassium);
the matrix expression of the above formula is:
S·Q＝N
in the formula:
s-sensitivity coefficient matrix, from S ij Of composition [ 5X 3]A matrix;
q-formula of uranium, thorium and potassium content in the formation, i.e. from Q j A 3-element formula of composition;
n-column of counting rates per energy window, from N i 5-element formula of the composition.
7. A gamma spectrometry logging method according to claim 6, wherein the energy window data of two detection devices and the determined sensitivity coefficient matrix are used to calculate the sensitivity coefficient according to the formula Q = S -1 N calculates the uranium, thorium and potassium content values.
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