A dual neutron detector integrated in the same location, logging instrument and application method

Abstract

The application discloses a same-position integrated double neutron detector, a logging instrument and an application method, and belongs to the field of uranium ore exploration logging. The double neutron detector comprises first and second scintillation crystals which are both sensitive to thermal neutrons and are arranged in a face-to-face manner, a photoelectric converter and a supporting portion; the first and second scintillation crystals and the photoelectric converter are arranged along the same axis to form a detection portion which is read out by a common light path, and the supporting portion is fixedly arranged outside the detection portion and supports the detection portion to be an integral component; a slow moderation layer is arranged on the outer wall surface of the first scintillation crystal except the bonding area; the logging instrument is provided with the double neutron detector, and the first and second scintillation crystals are calibrated in the same thermal neutron field during application; the spatial consistency error is eliminated through the same-position design of the double scintillation crystals; the hardware structure of the detector electronics is simplified through the common light path reading out design; and the detector module is convenient to integrate.

Description

Technical Field

[0001] This invention relates to the field of logging technology for uranium exploration, and more specifically, to a dual neutron detector, logging instrument, and application method integrated in the same location. Background Technology

[0002] Traditional pulsed neutron uranium logging tools require axially separated thermal neutron and ultrathermal neutron detectors, such as those using ³He tube gas detectors. Due to wellbore size limitations (typically less than 60mm in diameter), the spacing between the ultrathermal and thermal neutron detectors is usually large. Because the distribution of formation thermal neutrons along the well axis changes dynamically over time, the separate design of the ultrathermal and thermal neutron detectors means that the thermal neutron count cannot accurately reflect the neutron flux at the location of the ultrathermal neutron detector, introducing spatial inconsistency errors.

[0003] In the prior art, Chinese patent CN203515572U discloses a uranium fission transient neutron logging tool based on the ratio of hyperthermal neutrons to thermal neutrons. The tool's design discloses a dual-neutron detector and a dual-neutron time spectrometer, which internally include two sets of proportional counters, a polyethylene neutron moderator material surrounding the hyperthermal neutron detector, a cadmium metal casing surrounding the moderator material, a high-voltage power supply for the detector, a preamplifier, a shaping and discrimination circuit, and a pulse counter, time spectrum analysis, and buffering circuit for recording the output signals of the dual-neutron detector. The dual-neutron detector employs a quincunx structure, where the hyperthermal neutron detector is located at the center of the probe cross-section, and multiple small-volume thermal neutron detectors surround it, with the gaps filled with a hydrogen-rich neutron moderator material, forming a quincunx-shaped profile that places the two neutron detectors almost in the same axial position. This design of the dual-neutron detector minimizes the influence of factors affecting thermal neutron calculations, i.e., introduces fewer errors.

[0004] While the aforementioned improvements can enhance detection accuracy by reducing the positional difference between the ultrathermal neutron detector and the thermal neutron detector, the detectors suffer from several drawbacks. Firstly, their overall size is relatively large, making them inconvenient for use in small wellbores. Secondly, the installation design between the ultrathermal and thermal neutron detectors results in a distance between them, limiting the improvement in thermal neutron counting accuracy. Furthermore, this detector array requires seven readout electronics channels, leading to a complex hardware structure. Therefore, with the exploration of new materials and the increasing demands for detector accuracy, a new structural design for dual neutron detectors in logging tools is needed to meet application requirements. Summary of the Invention

[0005] 1. The technical problem that the invention aims to solve

[0006] The purpose of this invention is to overcome the limitations of existing uranium logging tools, which require axially separate thermal neutron and ultrathermal neutron detectors, resulting in thermal neutron counts that cannot accurately reflect the neutron flux at the location of the ultrathermal neutron detector and introducing spatial inconsistency errors. This invention employs a dual-scintillation crystal co-located common optical path design to achieve co-location of the thermal neutron detector and ultrathermal neutron detector along the logging tool's axis, which not only reduces size but also effectively improves detection accuracy. The common optical path design, combined with the electronic method of pulse waveform discrimination, simplifies multiple electronic channels into one, greatly improving the instrument's integration.

[0007] 2. Technical Solution

[0008] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0009] In a first aspect, the present invention provides a dual neutron detector integrated in the same location, comprising a first scintillation crystal, a second scintillation crystal, a photoelectric converter, and a support, wherein both the first scintillation crystal and the second scintillation crystal are thermal neutron-sensitive crystals.

[0010] A shielding and slowing layer is provided on the outer wall surface of the first scintillation crystal, and the first scintillation crystal and the shielding and slowing layer constitute a superthermal neutron detection unit; the second scintillation crystal constitutes a thermal neutron detection unit, the superthermal neutron detection unit and the thermal neutron detection unit are disposed in face-to-face contact, the photoelectric converter is coupled and disposed on the end face of the thermal neutron detection unit away from the superthermal neutron detection unit, and the superthermal neutron detection unit, the thermal neutron detection unit and the photoelectric converter constitute a detection unit with a common optical path readout along the same axis;

[0011] The support is fixed to the outside of the detector, and the detector is supported by an integral component.

[0012] Furthermore, the shielding and slowing layer includes a shielding layer and a slowing layer disposed inside the shielding layer;

[0013] The moderating layer covers all the outer surfaces of the first scintillation crystal, and the shielding layer covers the outer surfaces of the moderating layer;

[0014] The moderating layer is a polyethylene moderating layer or a paraffin moderating layer, and the shielding layer is a cadmium layer; necessarily, the thickness of the shielding layer needs to be able to block all thermal neutrons, and the thickness of the moderating layer needs to be able to slow down all hyperthermal neutrons into thermal neutrons.

[0015] Furthermore, the first scintillation crystal is selected from... 6 Li glass, Ce:LiCAF, 6 LiF / ZnS(Ag), CLYC, CLLB, LiI(Eu), zirconia crystal or EJ-299 plastic scintillator;

[0016] The second scintillation crystal is selected from 6 Li glass, Ce:LiCAF, 6 LiF / ZnS(Ag), CLYC, CLLB, LiI(Eu), zirconia crystal or EJ-299 plastic scintillator.

[0017] Furthermore, the support portion is configured as a closed housing that encloses the probe portion;

[0018] The enclosed housing includes a first housing and a second housing; the first housing is configured as a cavity structure with one end open; the second housing is connected to the first housing and includes at least an end cap that closes the opening; a chamber for accommodating the probe is formed between the first housing and the second housing, and the probe is detachably fixed within the cavity structure.

[0019] Furthermore, the surfaces of the ultrathermal neutron detection unit and the thermal neutron detection unit that are in contact with each other have the same shape and size.

[0020] Furthermore, the first scintillation crystal and the second scintillation crystal are regular hexahedral structures with the same shape.

[0021] In a second aspect, the present invention provides a co-located integrated dual-neutron logging tool, comprising a pulsed neutron source, a dual-neutron detector, a detector power supply, and a data acquisition and processing module, wherein the dual-neutron detector is the co-located integrated dual-neutron detector provided in the first aspect of the present invention.

[0022] Furthermore, the data acquisition and processing module includes a preamplifier, an analog-to-digital converter, and an FPGA processor. The FPGA processor is internally configured with a pulse counting module and a time spectrum analysis module. The detector power supply is connected to the photoelectric converter. The photoelectric converter receives optical signals and outputs electrical signals through a common optical path readout structure formed by the photoelectric converter, the hyperthermal neutron detection unit, and the thermal neutron detection unit. The output terminal of the photoelectric converter is connected to the preamplifier, and the output terminal of the preamplifier is connected to the analog-to-digital converter to amplify and shape the electrical signal output by the photoelectric converter into a digital signal. The output terminal of the analog-to-digital converter is connected to the FPGA processor to count thermal neutrons and hyperthermal neutrons. The output terminal of the FPGA processor is communicatively connected to a logging computer to upload the counting information for calculating the uranium content of the formation.

[0023] A third aspect of the present invention provides a method for applying the dual-neutron logging tool integrated at the same location as proposed in the second aspect of the present invention, comprising the following steps:

[0024] In the same thermal neutron field, the first scintillation crystal and the second scintillation crystal are calibrated, the ratio of thermal neutron detection efficiency between the crystals is calculated, and then the ratio of the first scintillation crystal's efficiency for ultrathermal neutron detection and the second scintillation crystal's efficiency for thermal neutron detection is determined.

[0025] The pulsed neutron source is activated to emit neutrons, and the pulse signals of thermal neutrons, hyperthermal neutrons, and gamma rays are collected based on the space structure read out by the common optical path of the detector.

[0026] Based on the pulse waveform discrimination algorithm, the collected pulse signals of thermal neutrons, hyperthermal neutrons and gamma rays are identified in real time. The pulse signals of thermal neutrons and hyperthermal neutrons are recorded, and the pulse signals of gamma rays are removed to obtain the time spectrum of thermal neutrons and the time spectrum of hyperthermal neutrons. The counts of thermal neutrons and hyperthermal neutrons are counted respectively.

[0027] Based on the ratio of the detection efficiency of the first scintillation crystal for hyperthermal neutrons to that of the second scintillation crystal for thermal neutrons, and the statistical hyperthermal neutron count and thermal neutron count, the flux ratio of hyperthermal neutrons to thermal neutrons is output.

[0028] The uranium content of the formation is calculated based on the flux ratio of ultrathermal neutrons to thermal neutrons.

[0029] Furthermore, the ratio of the thermal neutron detection efficiencies between the crystals in the application method is equal to the ratio of the thermal neutron detection efficiency of the first scintillation crystal to the thermal neutron detection efficiency of the second scintillation crystal.

[0030] 3. Beneficial effects

[0031] Compared with the prior art, the technical solution provided by this invention has the following advantages:

[0032] (1) The dual neutron detector integrated in the same position provided by the present invention adopts two scintillation crystals, both of which are sensitive to thermal neutrons, and are mounted face-to-face. One of the scintillation crystals is provided with a shielding and slowing layer on its outer wall, and the photoelectric converter is coupled to the opposite end face of the scintillation crystal without the shielding and slowing layer. The two scintillation crystals and the photoelectric converter constitute a detection unit with a common optical path readout. The scintillation crystal with the shielding and slowing layer constitutes an ultrathermal neutron detection unit, and the other scintillation crystal constitutes a thermal neutron detection unit. This detection unit not only has spatial consistency when installed in the logging tool, but the design of the two scintillation crystals in the same position also eliminates the spatial inconsistency error introduced by the axial separation of the thermal neutron detector and the ultrathermal neutron detector in the original logging tool. This makes the final thermal neutron count able to truly reflect the neutron flux at the position of the ultrathermal neutron detector, thus improving the detection accuracy. Moreover, the detection unit with a common optical path readout only needs one readout electronic channel when used in conjunction with the electronic method of pulse waveform discrimination. That is, the existing complex multi-channel electronic channel is simplified into one channel, which greatly improves the integration of the logging tool structure.

[0033] (2) The dual neutron detector integrated in the same position provided by the present invention adopts two scintillation crystals in combination, which greatly reduces the volume compared with the gas detector, the surrounding structure detector and the separate detector, and the structure is more compact; combined with the detection part to form a single probe structure detector, it can be adapted to small-sized wellbores.

[0034] (3) The dual neutron detector integrated in the same position provided by the present invention has a common optical path readout structure for the detection part, which ensures the consistency of the two scintillation crystals from the photoelectric converter to the signal readout circuit and does not introduce additional errors.

[0035] (4) When the dual-neutron logging instrument integrated in the same position provided by the present invention is applied, the thermal neutron detection efficiency is calibrated in the same thermal neutron field by utilizing the characteristics of two scintillation crystals, both of which are sensitive to thermal neutrons. Then, under the condition that the ultrathermal neutron detection unit shields thermal neutrons and the ultrathermal neutron slows down well, the ratio of the ultrathermal neutron detection unit's detection efficiency to the thermal neutron detection unit in the detection section can be directly obtained. When used for uranium content calculation, the uranium content can be directly obtained through the calibration coefficient by the flux ratio of ultrathermal neutrons to thermal neutrons. Attached Figure Description

[0036] Figure 1 This is a cross-sectional view of the dual neutron detector integrated at the same location according to the present invention;

[0037] Figure 2 This is a readout of the electronic system framework diagram for this invention.

[0038] Explanation of the labels in the diagram:

[0039] 101-First scintillation crystal; 102-Second scintillation crystal; 103-Shielding layer; 104-Slowing layer; 105-Photoelectric converter; 106-Support unit. Detailed Implementation

[0040] To further understand the content of this invention, a detailed description of the invention will be provided in conjunction with the accompanying drawings.

[0041] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0042] The present invention will be further described below with reference to embodiments.

[0043] Example 1

[0044] Combination Figure 1 As shown, the dual neutron detector integrated in the same position provided in this embodiment includes a first scintillation crystal 101, a second scintillation crystal 102, a photoelectric converter 105, and a support portion 106. Both the first scintillation crystal 101 and the second scintillation crystal 102 are crystals sensitive to thermal neutrons.

[0045] During design and installation, a shielding and slowing layer is provided on the outer wall surface of the first scintillation crystal 101, and the first scintillation crystal 101 and the shielding and slowing layer constitute a superthermal neutron detection unit; the second scintillation crystal 102 constitutes a thermal neutron detection unit, the superthermal neutron detection unit and the thermal neutron detection unit are arranged in close contact with each other, the photoelectric converter 105 is coupled to the end face of the thermal neutron detection unit away from the superthermal neutron detection unit, and the superthermal neutron detection unit, the thermal neutron detection unit and the photoelectric converter 105 are arranged along the same axis to form a detection part with a common optical path readout; the support part 106 is fixed to the outside of the detection part, and the support part of the detection part is an integral component, that is, forming a probe structure;

[0046] like Figure 1As shown, during detector assembly, all outer surfaces of the first scintillation crystal 101 are first covered with the shielding and slowing layer; one outer surface of the second scintillation crystal 102 is selected from below the first scintillation crystal and attached to the bottom surface of the first scintillation crystal 101 covered with the shielding and slowing layer, and the photoelectric converter 105 is disposed on the end surface of the second scintillation crystal 102 away from the bottom surface; defining the vertical direction as the up-down direction, the first scintillation crystal 101, the second scintillation crystal 102, and the photoelectric converter 105 are arranged sequentially in the top-down direction. In order to achieve the purpose of the first scintillation crystal 101, the second scintillation crystal 102, and the photoelectric converter 105 forming a common optical path for readout along the same axis, the first scintillation crystal 101 and the second scintillation crystal 102 are both configured as axially symmetric structures in the vertical direction, and the center of the photoelectric converter 105 is located on the axis.

[0047] In specific implementation, to facilitate assembly, the surfaces of the ultrathermal neutron detection unit and the thermal neutron detection unit that are in contact with each other are designed to have the same shape and size. In this embodiment, for ease of fabrication, the first scintillation crystal 101 and the second scintillation crystal 102 are designed as regular hexahedral structures with the same shape, such as cuboids or cubes, to ensure the stability of coaxial common optical path readout. Furthermore, the first scintillation crystal 101 is selected... 6 Li glass, the second scintillation crystal selected 6 LiF / ZnS(Ag); In addition, for ease of installation, the dimensions of the first scintillation crystal 101 and the second scintillation crystal 102 are selected to match the detector size.

[0048] As an optional implementation, the first scintillation crystal 101 may also be selected from Ce:LiCAF, 6 LiF / ZnS(Ag), CLYC, CLLB, LiI(Eu), zirconia crystal, or EJ-299 plastic scintillator; the second scintillator crystal 102 may also be selected from... 6 Li glass, Ce:LiCAF, CLYC, CLLB, LiI(Eu), zirconia crystal, or EJ-299 plastic scintillator; the photoelectric converter 105 is selected from PTM or SiPM.

[0049] Further integration Figure 1As shown, in this embodiment, the shielding and moderating layer covering the outer wall of the first scintillation crystal includes a shielding layer 103 and a moderating layer 104 disposed inside the shielding layer 103. The moderating layer 104 covers all areas of the outer wall surface of the first scintillation crystal 101. The moderating layer 104 is a polyethylene moderating layer or a paraffin moderating layer, used to modulate hyperthermal neutrons into thermal neutrons. The shielding layer 103 covers the outer wall surface of the moderating layer 104 and can be a cadmium layer or a gadolinium layer. In a specific implementation, the shielding layer 103 covers all the outer wall surfaces of the moderating layer 104. The shielding layer 103 is a cadmium layer, and the plating is achieved by electroplating. In this embodiment, the moderating layer 104 is a paraffin moderating layer. Naturally, the thickness of the shielding layer 103 needs to be sufficient to block all thermal neutrons, and the thickness of the moderating layer 104 needs to be sufficient to modulate all hyperthermal neutrons into thermal neutrons.

[0050] In this invention, the support part 106 serves to connect the ultrathermal neutron detection unit, the thermal neutron detection unit, and the photoelectric converter 105 into a single structure. Figure 1 In the illustrated embodiment, the support portion 106 is configured as a closed housing made of metal material, such as stainless steel, enclosing the detector portion; the closed housing includes a first housing and a second housing; the first housing is configured as a cavity structure with one end open; the second housing is connected to the first housing and includes at least an end cap that closes the opening; a cavity for accommodating the detector portion is formed between the first housing and the second housing, and the detector portion is detachably fixed within the cavity structure. In a specific implementation, the first housing or the second housing has mounting holes that communicate with the interior of the cavity structure, allowing the power lines and signal lines of the photoelectric converter 105 to pass through, thereby enabling power supply and signal output from the ultrathermal neutron detection unit and the thermal neutron detection unit.

[0051] As an optional implementation, both the first housing and the second housing are configured as hollow structures with one open end. The first housing and the second housing are respectively provided with a first support and a second support inside the first housing and the second housing. The bottom surface of the second housing opposite to the opening is provided with wire holes for power lines and signal lines to pass through. The outer wall of the first scintillation crystal 101 is covered with a shielding and slowing layer and then locked in the first support. The second scintillation crystal 102 is locked in the second support. The photoelectric converter 105 is coupled and disposed on the end face of the second scintillation crystal 102 away from the opening of the second housing. During assembly, the first housing and the second housing are connected and installed vertically with their openings facing each other. The open end of the first housing is fitted onto the outer wall of the open end of the second housing until the bottom surface of the first scintillation crystal 101 covered with the shielding and slowing layer is in contact with the top surface of the second scintillation crystal 102. The first scintillation crystal 101 and the second scintillation crystal 102 covered with the shielding and slowing layer are fixed in the first housing and the second housing respectively, and their positions correspond and their axes coincide in the vertical direction.

[0052] In the above embodiments, the first scintillation crystal 101 and the second scintillation crystal 102, coated with a shielding and moderating layer, are surface-mounted and connected to the photoelectric converter 105 to form a dual neutron detector. Structurally, this achieves co-location integration of the thermal neutron detection unit and the hyperthermal neutron detection unit. This not only results in a compact structure and small size, making it easier to adapt to small-sized wellbores, but also eliminates axial position errors when they are separately set on the logging tool, enabling more accurate acquisition of thermal and hyperthermal neutron counts at the detection location. Furthermore, by configuring the first scintillation crystal 101, the second scintillation crystal 102, and the photoelectric converter 105 as a coaxial common optical path readout structure, the consistency of the dual scintillation crystals from the photoelectric converter 105 to the signal readout circuit is ensured, preventing the introduction of additional errors that could cause inaccurate counting.

[0053] Example 2

[0054] This embodiment provides a dual-neutron logging tool integrated in the same location, including a pulsed neutron source, a dual-neutron detector, a detector power supply, and a data acquisition and processing module. The dual-neutron detector used in the logging tool is the dual-neutron detector integrated in the same location provided in Embodiment 1. Optionally, the data acquisition and processing module includes a preamplifier, an analog-to-digital converter (ADC), and an FPGA processor. The FPGA processor internally configures a pulse counting module and a time spectrum analysis module. During installation, the detector power supply is connected to the photoelectric converter 105 to power it. The photoelectric converter 105 outputs the optical signals generated by the first scintillation crystal 101 and the second scintillation crystal 102 as electrical signals via a common-path readout structure. The output of the photoelectric converter 105 is connected to the preamplifier, and the output of the preamplifier is connected to the ADC to amplify and shape the electrical signals output by the photoelectric converter, converting them into digital signals. The output of the ADC is connected to the FPGA processor to statistically analyze the counting information of thermal neutrons and hyperthermal neutrons. The output of the FPGA processor is communicatively connected to a logging computer to upload the counting information for calculating the uranium content of the formation. That is, as... Figure 2 The working principle of the readout electronics system of this logging tool is as follows: after acquiring and amplifying the output signal of the photoelectric converter 105, waveform discrimination is performed, and then the thermal neutron count and hyperthermal neutron count are statistically analyzed based on the discrimination results, and finally the count output is completed, which is used to accurately calculate the uranium content of the formation.

[0055] When a dual-neutron detector integrated in the same location is used in a logging tool, the hyperthermal neutron detection unit and the thermal neutron detection unit are located in the same position along the well depth axis and are spatially aligned. Therefore, when counting thermal neutrons, the neutron flux can accurately reflect the neutron flux of the hyperthermal neutron detection unit, resulting in more accurate detection results. Furthermore, the common optical path design of the dual-neutron detector, combined with the pulse waveform discrimination algorithm for the electrical readout electronics channel, simplifies multiple readout electronics channels into a single channel, significantly improving the instrument's integration.

[0056] Example 3

[0057] This embodiment proposes an application method for the dual-neutron logging tool integrated at the same location disclosed in Embodiment 2 above, which specifically includes the following steps:

[0058] 1) In the same thermal neutron field, calibrate the first scintillation crystal 101 and the second scintillation crystal 102, calculate the ratio of the thermal neutron detection efficiencies between the crystals, and then determine the ratio of the thermal neutron detection efficiency of the first scintillation crystal 101 to that of the second scintillation crystal 102. 1 / 2; When the shielding and moderation layer provides good shielding for thermal neutrons and moderates ultrathermal neutrons, the efficiency of detecting thermal neutrons incident on the first scintillation crystal 101 should be equal to its detection efficiency for thermal neutrons in a thermal neutron field; In addition, the first scintillation crystal 101 and the second scintillation crystal 102 can be calibrated synchronously or asynchronously.

[0059] 2) Activate the pulsed neutron source to emit neutrons, and collect pulse signals of thermal neutrons, hyperthermal neutrons, and gamma rays based on the space structure read out by the common optical path of the detector;

[0060] 3) The collected pulse signals of thermal neutrons, hyperthermal neutrons, and gamma rays are identified in real time based on the pulse waveform discrimination algorithm. The pulse signals of thermal neutrons and hyperthermal neutrons are recorded, and the pulse signals of gamma rays are removed to obtain the time spectra of thermal neutrons and hyperthermal neutrons. The counts of thermal neutrons N2 and hyperthermal neutrons N1 are counted respectively. The pulse waveform discrimination algorithm is used to distinguish the hyperthermal neutron pulse signals and thermal neutron pulse signals, which can effectively distinguish the interference of the gamma signal during neutron detection. The pulse waveform discrimination algorithm is preset in the FPGA processor.

[0061] 4) Based on the ratio of the detection efficiency of the first scintillation crystal 101 for ultrathermal neutrons to the detection efficiency of the second scintillation crystal 102 for thermal neutrons. 1 / 2. Simultaneously count the hyperthermal neutron count N1 and the thermal neutron count N2, and output the flux ratio R of hyperthermal neutrons to thermal neutrons, R = n1 / n2 = (N1 / 1) / (N2 / 2); where n1 represents the ultrathermal neutron flux at the detection location, and n2 represents the thermal neutron flux at the detection location;

[0062] 5) Calculate the uranium content of the formation based on the flux ratio of ultrathermal neutrons to thermal neutrons; the calculation formula is as follows:

[0063] P U = k R = k (N1 / 1) / (N2 / 2);

[0064] In the formula, k This indicates the calibration coefficient of the logging instrument.

[0065] This embodiment utilizes the characteristics of two scintillation crystals, both sensitive to thermal neutrons, to calibrate thermal neutron detection efficiency in the same thermal neutron field. It directly obtains the ratio of the detection efficiency of the ultrathermal neutron detection unit to that of the thermal neutron detection unit within the detection section, eliminating the need to calibrate thermal neutron flux and ultrathermal neutron flux using multiple influencing factors. 1 / The value of 2 is used for calculation, effectively reducing the computational load. Furthermore, when the dual neutron detector integrated in the same location provided by this invention is used for uranium content calculation, the uranium content can be directly obtained by converting the flux ratio of hyperthermal neutrons to thermal neutrons using a calibration coefficient, making the calculation convenient.

[0066] The present invention and its embodiments have been described above illustratively. This description is not restrictive and is merely one embodiment of the present invention, and is not actually limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A dual neutron detector integrated in the same location, characterized in that, It includes a first scintillation crystal, a second scintillation crystal, a photoelectric converter, and a support. Both the first and second scintillation crystals are sensitive to thermal neutrons. The first and second scintillation crystals are calibrated in the same thermal neutron field to calculate the ratio of the thermal neutron detection efficiency between the crystals, thereby determining the ratio of the thermal neutron detection efficiency of the first scintillation crystal to that of the second scintillation crystal. A shielding and slowing layer is disposed on the outer wall surface of the first scintillation crystal, and the first scintillation crystal and the shielding and slowing layer constitute a superthermal neutron detection unit; the second scintillation crystal constitutes a thermal neutron detection unit, and the superthermal neutron detection unit and the thermal neutron detection unit are disposed face-to-face, with the face shapes and sizes of the face-to-face surfaces of the superthermal neutron detection unit and the thermal neutron detection unit being identical; a photoelectric converter is coupled to the end face of the thermal neutron detection unit away from the superthermal neutron detection unit, and the superthermal neutron detection unit, the thermal neutron detection unit, and the photoelectric converter constitute a detection unit with a common optical path readout along the same axis; wherein, the shielding and slowing layer includes a shielding layer and a slowing layer disposed inside the shielding layer; the slowing layer covers all the outer wall surfaces of the first scintillation crystal, and the shielding layer covers the outer wall surface of the slowing layer; The support is fixed to the outside of the detector, and the detector is supported by an integral component.

2. The co-located dual neutron detector according to claim 1, characterized in that, The first scintillation crystal is selected from 6 Li glass, Ce:LiCAF, 6 LiF / ZnS(Ag), CLLB, LiI(Eu), zirconia crystal or EJ-299 plastic scintillator; The second scintillation crystal is selected from 6 Li glass, Ce:LiCAF, 6 LiF / ZnS(Ag), CLLB, LiI(Eu), zirconia crystal or EJ-299 plastic scintillator.

3. The co-located dual neutron detector according to claim 1, characterized in that, The support portion is configured as a closed shell that encloses the detector portion; The enclosed housing includes a first housing and a second housing; the first housing is configured as a cavity structure with one end open; the second housing is connected to the first housing and includes at least an end cap that closes the opening; a chamber for accommodating the probe is formed between the first housing and the second housing, and the probe is detachably fixed within the cavity structure.

4. The co-located dual neutron detector according to claim 1, characterized in that, The first scintillation crystal and the second scintillation crystal are regular hexahedral structures with the same shape.

5. A dual-neutron logging tool integrated in the same location, comprising a pulsed neutron source, dual neutron detectors, a detector power supply, and a data acquisition and processing module, characterized in that, The dual neutron detector is a co-located dual neutron detector as described in any one of claims 1-4.

6. The dual-neutron logging tool integrated in the same location according to claim 5, characterized in that, The data acquisition and processing module includes a preamplifier, an analog-to-digital converter (ADC), and an FPGA processor. The FPGA processor internally includes a pulse counting module and a time spectrum analysis module. The detector power supply is connected to the photoelectric converter. The photoelectric converter, together with the hyperthermal neutron detection unit and the thermal neutron detection unit, forms a common optical path readout structure to receive optical signals and output electrical signals. The output of the photoelectric converter is connected to the preamplifier, and the output of the preamplifier is connected to the ADC to amplify and shape the electrical signal output by the photoelectric converter, converting it into a digital signal. The output of the ADC is connected to the FPGA processor for statistical analysis of thermal and hyperthermal neutron counts. The output of the FPGA processor is connected to the logging computer to upload the counting information for calculating the uranium content of the formation.

7. The application method of the dual-neutron logging tool integrated at the same location according to claim 5, characterized in that, Includes the following steps: In the same thermal neutron field, the first scintillation crystal and the second scintillation crystal are calibrated, the ratio of thermal neutron detection efficiency between the crystals is calculated, and then the ratio of the first scintillation crystal's efficiency for ultrathermal neutron detection and the second scintillation crystal's efficiency for thermal neutron detection is determined. The pulsed neutron source is activated to emit neutrons, and the pulse signals of thermal neutrons, hyperthermal neutrons, and gamma rays are collected based on the space structure read out by the common optical path of the detector. Based on the pulse waveform discrimination algorithm, the collected pulse signals of thermal neutrons, hyperthermal neutrons and gamma rays are identified in real time. The pulse signals of thermal neutrons and hyperthermal neutrons are recorded, and the pulse signals of gamma rays are removed to obtain the time spectrum of thermal neutrons and the time spectrum of hyperthermal neutrons. The counts of thermal neutrons and hyperthermal neutrons are counted respectively. Based on the ratio of the detection efficiency of the first scintillation crystal for hyperthermal neutrons to that of the second scintillation crystal for thermal neutrons, and the statistical hyperthermal neutron count and thermal neutron count, the flux ratio of hyperthermal neutrons to thermal neutrons is output. The uranium content of the formation is calculated based on the flux ratio of ultrathermal neutrons to thermal neutrons.

8. The application method of the dual-neutron logging tool integrated at the same location according to claim 7, characterized in that, The ratio of the thermal neutron detection efficiencies between the crystals is equal to the ratio of the thermal neutron detection efficiencies of the first scintillation crystal to the ultrathermal neutron detection efficiencies of the second scintillation crystal to the thermal neutron detection efficiencies.

Images