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 a thermal neutron detector and an epithermal neutron detector which are arranged in a nested mode; the thermal neutron detector is arranged as a first microstructure gas detector, and comprises a ring chamber structure with an axial through hole and filled with 3He gas, a cathode drift electrode and an anode readout electrode; a detection part of the epithermal neutron detector is embedded in the axial through hole, and the epithermal neutron detector can be arranged as a scintillation crystal detector coated with a shielding slowing layer or a second microstructure gas detector. Compared with the prior art, the nested structure fundamentally solves the inherent problem of spatial inconsistency of the conventional separated detector, and greatly improves the calculation precision of uranium content; meanwhile, the epithermal neutron detector has two implementable schemes, and has high structural flexibility.

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 ultrathermal neutron and thermal 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 thermal neutron flux at the location of the ultrathermal neutron detector, introducing spatial inconsistency errors.

[0003] In the prior art, by reducing the installation position of the ultrathermal neutron detector and the thermal neutron detector along the axis of the logging tool, the distance between the two is reduced, thereby reducing the error of the thermal neutron flux of the ultrathermal neutron detector relative to the installation position of the thermal neutron detector. For example, 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 includes a dual neutron detector and a dual neutron time spectrometer, comprising two sets of proportional counters, a polyethylene neutron moderator encasing the hyperthermal neutron detector, a cadmium metal casing surrounding the moderator, 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. Specifically, the dual neutron detector adopts 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 are located around it, with the gaps filled with a hydrogen-rich neutron moderator, forming a quincunx-shaped profile so that the two neutron detectors are almost in the same axial position. This design of the dual neutron detector minimizes the influence of correction factors on thermal neutron calculations, i.e., introduces fewer errors. The quincunx-shaped outline arrangement of the thermal neutron detector and the ultrathermal neutron detector effectively reduces the axial position difference between the two detectors, thereby improving detection accuracy.

[0004] However, the overall structure of the aforementioned detector is relatively large and has seven readout electronic channels, which makes it inconvenient to use in small-sized wellbores. If the structure is miniaturized for use in small-sized wellbores, the manufacturing process is complex. Therefore, it is necessary to improve the structure of the dual neutron detector to meet the requirements of small-sized wellbore applications. Summary of the Invention

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

[0006] The purpose of this invention is to address the problem that existing uranium logging tools, which use axially separated thermal neutron and hyperthermal neutron detectors in the same location, cannot accurately reflect the neutron flux at the location of the hyperthermal neutron detector, thus introducing spatial inconsistency errors. Furthermore, these instruments are often too large for small wellbores and have complex structures. This invention proposes a newly designed, small-sized, and co-located integrated dual neutron detector with fewer readout electronic channels.

[0007] 2. Technical Solution

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

[0009] In a first aspect, this invention proposes a co-located integrated dual neutron detector, comprising a nested thermal neutron detector and a superthermal neutron detector. The thermal neutron detector has a through-hole in its center, and the detection part of the superthermal neutron detector is embedded within the through-hole, forming an integral structure with the thermal neutron detector. This nested design achieves co-located integration of the thermal and superthermal neutron detectors, effectively eliminating spatial positional errors when used on a logging tool, and achieving dual-function integration without increasing the radial dimension of the instrument.

[0010] Furthermore, the thermal neutron detector is configured as a first microstructure gas detector, which includes an annular chamber structure with an axial through hole, the annular chamber structure being filled with ³He gas; a cathode drift electrode and an anode readout electrode are respectively provided at both ends of the annular chamber structure along its axial direction, and the cathode drift electrode and the anode readout electrode are respectively connected to the internal chamber of the annular chamber structure.

[0011] Furthermore, the ultrathermal neutron detector includes a scintillation crystal, a photoelectric converter, and a first shielding moderation layer. The scintillation crystal is a crystal sensitive to thermal neutrons. The photoelectric converter is coupled to the axial end face of any of the scintillation crystals, and the first shielding moderation layer covers all the outer wall faces of the scintillation crystals. The axial direction of the scintillation crystal is defined to be parallel to the axial direction of the through-hole.

[0012] The scintillation crystal and the first shielding and moderating layer constitute a superthermal neutron detection unit. The superthermal neutron detection unit is embedded in the axial through-hole of the first microstructure gas detector, and the dimension of the superthermal neutron detection unit along the axial direction of the through-hole is adapted to the dimension of the through-hole along its axial direction. Optionally, the scintillation crystal covering the first shielding and moderating layer is supported and embedded in the through-hole by a support member.

[0013] Furthermore, the superthermal neutron detector includes a second microstructure gas detector and a second shielding and slowing layer. The second shielding and slowing layer covers all the outer surfaces of the second microstructure gas detector. The superthermal neutron detector is integrally embedded in the through-hole, and its axial dimension along the through-hole is adapted to the axial dimension of the through-hole. Optionally, the second microstructure gas detector covered by the second shielding and slowing layer is supported and embedded in the through-hole by a support member. Optionally, both the first and second shielding and slowing layers include a shielding layer and a slowing layer disposed inside the shielding layer. The slowing layer covers all the outer surfaces of the second microstructure gas detector or all the outer surfaces of the scintillation crystal, and the shielding layer covers the outer surface of the slowing layer. The slowing layer is a polyethylene slowing layer or a paraffin slowing layer, and the shielding layer is a cadmium layer or a gadolinium layer. Essentially, the thickness of the shielding layer needs to be sufficient to block all thermal neutrons, and the thickness of the slowing layer needs to be sufficient to slow down all superthermal neutrons into thermal neutrons.

[0014] Furthermore, the dual neutron detector also includes a metal housing, which is enclosed and fitted over the outside of the thermal neutron detector and the ultrathermal neutron detector.

[0015] Furthermore, the scintillation crystal is selected from... 6 Li glass, Ce:LiCAF, 6 The scintillator is made of LiF / ZnS(Ag), CLYC, CLLB, LiI(Eu), zirconia crystal, or EJ-299 plastic scintillator; preferably, the scintillator crystal has a regular hexahedral structure.

[0016] 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 data acquisition and processing module, and a detector power supply for supplying power to the pulsed neutron source, the dual-neutron detector, and the data acquisition and processing module, wherein the dual-neutron detector is any co-located integrated dual-neutron detector proposed in the first aspect above.

[0017] Furthermore, the data acquisition and processing module includes a first signal processing channel, a second signal processing channel, an analog-to-digital converter, and an FPGA processor;

[0018] The first and second signal processing channels have identical components, each including a preamplifier and a filter shaper connected in sequence. The input of the preamplifier in the first signal processing channel is connected to the thermal neutron detector, and the output is connected to the filter shaper of the first signal processing channel. The input of the preamplifier in the second signal processing channel is connected to the ultrathermal neutron detector, and the output is connected to the filter shaper of the second signal processing channel. The output of each filter shaper is connected to the analog-to-digital converter (ADC) to convert the detection signals from the thermal neutron detector and the ultrathermal neutron detector into digital signals, respectively. The output of the ADC is connected to the FPGA processor, which is internally configured with a pulse counting module and a time spectrum analysis module for statistically analyzing the count information of thermal and ultrathermal neutrons. The output of the FPGA processor is communicatively connected to a logging computer to upload the count information for calculating the uranium content of the formation.

[0019] 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:

[0020] In the same thermal neutron field, the thermal neutron detector and the ultrathermal neutron detector without a first or second shielding moderation layer are calibrated, and the ratio of their thermal neutron detection efficiencies is calculated to determine the ratio of the thermal neutron detector's thermal neutron detection efficiency to the ultrathermal neutron detector's ultrathermal neutron detection efficiency.

[0021] The pulsed neutron source is activated to emit neutrons. The thermal neutron signal and the hyperthermal neutron signal are processed based on the first signal processing channel and the second signal processing channel, respectively. The thermal neutron time spectrum and the hyperthermal neutron time spectrum are collected.

[0022] Based on the collected thermal neutron time spectrum and the ultrathermal neutron time spectrum, the thermal neutron count and ultrathermal neutron count are counted respectively.

[0023] Based on the ratio of the thermal neutron detector's thermal neutron detection efficiency to the ultrathermal neutron detector's ultrathermal neutron detection efficiency, and the statistical counts of thermal neutrons and ultrathermal neutrons, the flux ratio of ultrathermal neutrons to thermal neutrons is output.

[0024] The uranium content of the formation is calculated based on the flux ratio of ultrathermal neutrons to thermal neutrons.

[0025] Furthermore, the ratio of the thermal neutron detection efficiency of the thermal neutron detector to that of the ultrathermal neutron detector without a first or second shielding moderation layer is equal to the ratio between the thermal neutron detector's thermal neutron detection efficiency and the ultrathermal neutron detector's ultrathermal neutron detection efficiency.

[0026] 3. Beneficial effects

[0027] Compared with the prior art, the technical solution provided by this invention has the following advantages:

[0028] (1) The dual neutron detector integrated in the same position provided by the present invention adopts a nested design in terms of structure. The outer thermal neutron detector is set as an annular chamber structure with an axial through hole, and the ultrathermal neutron detector is embedded in the axial through hole, so as to realize the axial co-position setting of the thermal neutron detector and the ultrathermal neutron detector. Among them, the thermal neutron detector is a microstructure gas detector, which limits the overall size of the dual neutron detector. The nested design of the dual neutron detector of the present invention, on the one hand, realizes the measurement of the two core functional components under strict source distance conditions through ingenious mechanical and functional integration, fundamentally eliminating the error caused by the spatial separation of the thermal neutron detector and the ultrathermal neutron detector, so that the final thermal neutron count can truly reflect the neutron flux at the position of the ultrathermal neutron detector, and improve the detection accuracy and reliability of uranium mine logging; on the other hand, when the dual neutron logging tool integrated in the same position provided by the present invention is applied, compared with the existing solution, the number of electronic channels can be reduced to a minimum of 2, which effectively reduces the complexity of the logging tool tube structure and increases the advantages of the tube space, and can make a logging tool with a size smaller than the wellbore diameter at a lower cost.

[0029] (2) The dual neutron detectors integrated in the same location provided by the present invention have two designs for the superthermal neutron detectors: a microstructure gas detector with a shielding moderation layer or a scintillation crystal detector. The scintillation crystal detector is easier to miniaturize and integrate than the microstructure gas detector, but the size of both is significantly smaller than that of the existing winding structure detector and the separate detector. In specific implementation, different superthermal neutron detectors can be selected according to the wellbore size, process cost and performance requirements of the application scenario.

[0030] (3) The dual neutron detectors integrated in the same position provided by the present invention make full use of the internal space of the thermal neutron detector by setting up the ultrathermal neutron detector, and achieve functional integration without increasing the radial size of the instrument, which is particularly suitable for small well environments; in addition, the integrated design reduces the connection points of downhole instruments and external cables, reduces the failure rate, and the dual neutron detectors are more reliable.

[0031] (4) When the dual-neutron logging tool integrated in the same position provided by the present invention is applied, the thermal neutron detector and the hyperthermal neutron detector without the first or first shielding moderation layer are calibrated in the same thermal neutron field to obtain the ratio of the thermal neutron detection efficiencies of the two detectors; when the first or first shielding moderation layer provides good shielding for thermal neutrons and hyperthermal neutron moderation, the ratio of the hyperthermal neutron detector's detection efficiency for hyperthermal neutrons to the thermal neutron detector's detection efficiency for thermal neutrons 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 hyperthermal neutrons to thermal neutrons; not only is complex calculation unnecessary, but the efficiency of uranium content calculation is greatly improved. Attached Figure Description

[0032] Figure 1 This is a cross-sectional view of the dual neutron detector integrated at the same location according to the present invention;

[0033] Figure 2 This is a readout of the electronic system framework diagram for this invention.

[0034] Explanation of the labels in the diagram:

[0035] 101-Cathode drift electrode; 102-Anode readout electrode; 103-Axial through hole; 104-Scintillator crystal; 105-Photoconverter; 106-Moderizing layer; 107-Shielding layer; 108-Metal casing. Detailed Implementation

[0036] To further understand the content of this invention, a detailed description of the invention will be provided in conjunction with the accompanying drawings.

[0037] 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.

[0038] The present invention will be further described below with reference to embodiments.

[0039] Example 1

[0040] Combination Figure 1As shown, the dual neutron detector integrated in the same location provided in this embodiment includes a nested thermal neutron detector and a superthermal neutron detector. The thermal neutron detector is configured as a first microstructure gas detector, which includes an annular cavity structure with an axial through-hole 103, and the annular cavity structure is filled with He gas. The first microstructure gas detector can be fabricated using printed circuit board (PCB) or silicon wafer technology to create microstructure electrodes, and the cavity is sealed by a ceramic or metal frame. The diameter of the axial through-hole 103 is 5~15mm to accommodate superthermal neutron detectors of different sizes. A cathode drift electrode 101 and an anode readout electrode 102 are respectively provided at both ends of the annular cavity structure along its axial direction, and the cathode drift electrode 101 and the anode readout electrode 102 are respectively connected to the internal cavity of the annular cavity structure. The field cage inside the annular cavity needs to be configured according to the shape of the cavity to form a uniform and strong electric field inside the cavity for particle detection.

[0041] The superthermal neutron detector includes a scintillation crystal 104, a photoelectric converter 105, and a first shielding and slowing layer. The scintillation crystal 104 is a crystal sensitive to thermal neutrons. During assembly, the photoelectric converter 105 is coupled to the axial end face of any of the scintillation crystals 104, and the first shielding and slowing layer covers all the outer wall faces of the scintillation crystal 104. The axial direction of the scintillation crystal 104 is defined to be parallel to the axial direction of the axial through-hole 103. The first shielding and slowing layer includes a shielding layer 107 with a thickness of 0.2~0.8 mm and a shielding layer 107 disposed on the shielding layer 104. 7. An internal moderating layer 106 with a thickness of 1~10mm; the moderating layer 106 covers all the outer wall surfaces of the scintillation crystal 104, and the shielding layer 107 covers the outer wall surface of the moderating layer 106; the scintillation crystal 104 and the first shielding and moderating layer constitute a superthermal neutron detection unit, the superthermal neutron detection unit is embedded in the axial through hole 103 of the first microstructure gas detector, and the dimension of the superthermal neutron detection unit along the axial direction of the axial through hole 103 is adapted to the dimension of the axial through hole along its axial direction, that is, the superthermal neutron detection unit is not exposed outside the axial through hole 103.

[0042] In this embodiment, the scintillation crystal 104 is configured as a regular hexahedral structure, i.e., a cuboid. The diameter of the outer circle of the cuboid can be adapted to the diameter of the axial through hole 103. The direction of the first microstructure gas detector's axial upward cathode drift electrode 101 is defined as upward and the direction of the anode readout electrode 102 is defined as downward. Then, the photoelectric converter 105 is disposed on the bottom surface of the cuboid.

[0043] Furthermore, the scintillation crystal 104 described in the embodiment is selected 6The glass is Li glass, the moderating layer 106 is a polyethylene moderating layer, the shielding layer 107 is a cadmium layer, and the coating is achieved by electroplating; the photoelectric converter 105 is a SiPM.

[0044] As an optional implementation, the scintillation crystal 104 may also be selected from Ce:LiCAF, 6 The material can be LiF / ZnS(Ag), CLYC, CLLB, LiI(Eu), zirconia crystal, or EJ-299 plastic scintillator; the moderating layer 106 can also be a paraffin moderating layer, the shielding layer can also be a gadolinium layer; and the photoelectric converter 105 can also be a PTM.

[0045] Further integration Figure 1 As shown, the dual neutron detector also includes a metal housing 108, which is enclosed and sleeved on the outside of the thermal neutron detector and the ultrathermal neutron detector to define the field of view of the dual neutron detector and reduce background interference. In the figure, the metal housing 108 can be designed as a housing structure with a top cover made of stainless steel, and the dual neutron detector is fixed as a whole and then fixedly installed in the housing structure.

[0046] As an optional implementation, the metal housing 108 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 dual neutron detectors is formed between the first housing and the second housing, and the thermal neutron detector and the ultrathermal neutron detector are respectively fixed to the first housing and the second housing; in specific use, the first housing or the second housing is fitted together, and when the first housing or the second housing is fitted to a set position, the detection part of the ultrathermal neutron detector is precisely embedded in the through hole of the thermal neutron detector. In this implementation, the thermal neutron detector and the ultrathermal neutron detector do not directly contact each other, but the metal housing serves as a support structure for the thermal neutron detector and the ultrathermal neutron detector to be relatively fixed.

[0047] In the above embodiments, the outer thermal neutron detector is configured as an annular cavity structure with an axial through hole, and the ultrathermal neutron detector is nested within the axial through hole 103. Without increasing the radial dimension of the instrument, the thermal neutron detector and the ultrathermal neutron detector are integrated into a axially co-position function. The nested structure fundamentally solves the inherent problem of inconsistent space in traditional separate dual neutron detectors, which not only has a small size but also greatly improves the accuracy of uranium content calculation.

[0048] Example 2

[0049] The dual neutron detector integrated in the same location provided in this embodiment includes a nested thermal neutron detector and an ultrathermal neutron detector. The thermal neutron detector is configured as a first microstructure gas detector, which includes an annular chamber structure with an axial through-hole 103, and the annular chamber structure is filled with He gas. The diameter of the axial through-hole 103 is 5-15 mm. A cathode drift electrode 101 and an anode readout electrode 102 are respectively provided at both ends of the annular chamber structure along its axial direction, and the cathode drift electrode 101 and the anode readout electrode 102 are respectively connected to the internal chamber of the annular chamber structure.

[0050] The superthermal neutron detector is fixed within the axial through-hole 103 of the first microstructure gas detector. It includes a second microstructure gas detector and a second shielding and slowing layer. The second shielding and slowing layer covers all the outer wall surfaces of the second microstructure gas detector. The dimension of the second microstructure gas detector covered with the second shielding and slowing layer along the axial direction of the axial through-hole 103 is adapted to the dimension of the axial through-hole along its axial direction, that is, the superthermal neutron detection unit is not exposed outside the axial through-hole 103. Optionally, in the embodiment, the second microstructure gas detector is set as a cylindrical structure. The outer diameter of the cylindrical structure after covering the second shielding and slowing layer is adapted to the inner diameter of the axial through-hole 103, ensuring that the superthermal neutron detector can be fixed within the axial through-hole 103.

[0051] Define the direction of the upward-pointing cathode drift electrode 101 of the first microstructure gas detector as "upward" and the direction of the anode readout electrode 102 as "downward". Then, the second microstructure gas detector includes a cylindrical chamber structure, a second cathode drift electrode sealing the upper surface of the cylindrical chamber structure, and a second anode readout electrode sealing the lower surface of the cylindrical chamber structure. The cylindrical chamber structure is filled with He gas. The structure of the second shielding and moderating layer is consistent with the composition and material of the first shielding and moderating layer, including a second shielding layer with a thickness of 0.2~0.8 mm and a second moderating layer with a thickness of 1~10 mm disposed inside the second shielding layer. The second moderating layer covers all the outer wall surfaces of the second microstructure gas detector, and the second shielding layer covers the outer wall surface of the second moderating layer.

[0052] The dual neutron detector also includes a metal housing 108 for defining the field of view of the dual neutron detector and reducing background interference. The metal housing 108 is enclosed and sleeved on the outside of the thermal neutron detector and the ultrathermal neutron detector.

[0053] Example 3

[0054] This embodiment provides a co-located integrated dual-neutron logging tool, including a pulsed neutron source, a dual-neutron detector, a data acquisition and processing module, and a detector power supply for powering the pulsed neutron source, the dual-neutron detector, and the data acquisition and processing module. The dual-neutron detector used in the logging tool is the co-located integrated dual-neutron detector provided in Embodiment 1. The data acquisition and processing module includes a first signal processing channel, a second signal processing channel, an analog-to-digital converter, and an FPGA processor. During design and assembly, the first and second signal processing channels have identical components, each including a preamplifier and a filter shaper connected in sequence. The input terminal of the preamplifier of the first signal processing channel is connected to the anode readout electrode 102 of the first microstructure gas detector, and the output terminal is connected to the filter shaper of the first signal processing channel. The second... The input of the preamplifier in the signal processing channel is connected to the photoelectric converter 105, and the output is connected to the filter shaper in the second signal processing channel. The outputs of the filter shaper are all connected to the analog-to-digital converter (ADC) to convert the detection signals from the thermal neutron detector and the hyperthermal neutron detector into digital signals, respectively. The preamplifier outputs the signal collected by the anode readout electrode 102 and the optical signal generated by the scintillation crystal. The ADC converts the input signal into a digital signal. The output of the ADC is connected to the FPGA processor, which is internally configured with a pulse counting module and a time spectrum analysis module for statistically analyzing the count information of thermal and hyperthermal neutrons. The output of the FPGA processor is communicatively connected to the logging computer to upload the count 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: the output signals of the anode readout electrode 102 and the photoelectric converter 105 are collected, amplified, filtered and shaped by two signal processing channels, then the waveform is digitized and digital signal is processed, and finally thermal neutron counting and hyperthermal neutron counting are performed to complete the count output.

[0055] The logging tool provided in this embodiment uses a dual neutron detector integrated in the same location. Because the dual neutron detectors employ a nested design, it ensures that the hyperthermal neutron detector and the thermal neutron detector are installed at the same position along the well depth axis of the logging tool, guaranteeing spatial consistency. Therefore, when counting thermal neutrons, the neutron flux accurately reflects the neutron flux of the hyperthermal neutron detector, resulting in more accurate and reliable uranium content detection results. Simultaneously, only two readout electronics channels are set inside the tube, reducing structural complexity and maximizing the use of internal space. When the flux is high, the number of readout electronics channels for the microstructure gas detector can be further increased.

[0056] Example 4

[0057] This embodiment proposes a co-located integrated dual-neutron logging tool, including a pulsed neutron source, a dual-neutron detector, a data acquisition and processing module, and a detector power supply for powering the pulsed neutron source, the dual-neutron detector, and the data acquisition and processing module. The only difference from Embodiment 3 is that the dual-neutron detector used in this logging tool is the co-located integrated dual-neutron detector provided in Embodiment 2. Furthermore, the input terminal of the preamplifier of the first signal processing channel is connected to the anode readout electrode 102 of the first microstructure gas detector, and the output terminal is connected to the filter shaper of the first signal processing channel. The input terminal of the preamplifier of the second signal processing channel is connected to the second anode readout electrode of the second microstructure gas detector, and the output terminal is connected to the filter shaper of the second signal processing channel. The output terminals of the filter shaper are all connected to the analog-to-digital converter.

[0058] Example 5

[0059] This embodiment proposes an application method for the dual-neutron logging tool integrated at the same location disclosed in Embodiment 3 above, which specifically includes the following steps:

[0060] 1) In the same thermal neutron field, calibrate the thermal neutron detector and the ultrathermal neutron detector without the first shielding moderation layer, calculate the ratio R1 of their thermal neutron detection efficiencies, and then determine the ratio R2 of the thermal neutron detector's thermal neutron detection efficiency and the ultrathermal neutron detector's ultrathermal neutron detection efficiency. Since the calibration condition is in the same thermal neutron field, their thermal neutron fluxes are equal, and the ratio of their detected thermal neutron fluxes is equal to the ratio of their thermal neutron detection efficiencies. Therefore, under the condition that the first shielding moderation layer provides good thermal neutron shielding and ultrathermal neutron moderation, the efficiency of thermal neutrons incident on the scintillation crystal 104 in being detected should theoretically be equal to its thermal neutron detection efficiency in the thermal neutron field, i.e., theoretically R1 = R2.

[0061] 2) Start the pulsed neutron source to emit neutrons, process the thermal neutron signal and the hyperthermal neutron signal based on the first signal processing channel and the second signal processing channel respectively, and collect the thermal neutron time spectrum and the hyperthermal neutron time spectrum;

[0062] 3) Based on the collected thermal neutron time spectrum and ultrathermal neutron time spectrum, count the thermal neutron count N1 and ultrathermal neutron count N2 respectively;

[0063] 4) Based on the ratio of the thermal neutron detector's thermal neutron detection efficiency to the ultrathermal neutron detector's ultrathermal neutron detection efficiency, and the concurrently counted thermal neutron counts N1 and N2, output the flux ratio R of ultrathermal neutrons to thermal neutrons.

[0064] 5) Calculate the uranium content of the formation based on the flux ratio R of ultrathermal neutrons to thermal neutrons; the calculation formula is as follows:

[0065] P U = k*R = k* (N2 / φ2) / (N1 / φ1);

[0066] In the formula, k This indicates the calibration coefficient of the logging instrument.

[0067] Specifically, when the first microstructure gas detector performs thermal neutron detection, thermal neutrons in the stratum can freely enter the ³He gas region of the first microstructure gas detector, generate ionized particles through the ³He(n,p)T reaction, and are collected by the anode readout electrode 102. After data acquisition and processing, the thermal neutron count N1 is obtained. N1 is proportional to the thermal neutron flux n1 at the detection location, i.e., N1 = φ1*n1, where φ1 represents the thermal neutron detection efficiency of the first microstructure gas detector. When the scintillation crystal detector with the first shielding moderation layer performs hyperthermal neutron detection, hyperthermal neutrons in the stratum must first pass through the first shielding moderation layer. The cadmium layer in the layer blocks and absorbs thermal neutrons, while the hyperthermal neutrons are moderated into thermal neutrons by the polyethylene layer before entering the scintillation crystal and being recorded. After data acquisition and processing, the hyperthermal neutron count N2 is obtained. N2 is proportional to the hyperthermal neutron flux n2 at the detection location, i.e., N2 = φ2*n2, where φ2 represents the hyperthermal neutron detection efficiency of the hyperthermal neutron detector.

[0068] Therefore, the flux ratio of superthermal neutrons to thermal neutrons is R = n2 / n1 = (N2 / φ2) / (N1 / φ1).

[0069] The application method in this embodiment is based on the nested structure design of thermal neutron detectors and ultrathermal neutron detectors. Therefore, the thermal neutron detector can be used to calibrate the thermal neutron detection efficiency in the same thermal neutron field, and the ratio of the thermal neutron detector's detection efficiency for thermal neutrons to that of the ultrathermal neutron detector can be directly obtained. The calculation is performed using the value of R2, without the need to use multiple influencing factors to calibrate the values ​​of thermal neutron count and ultrathermal neutron count, effectively reducing the amount of calculation.

[0070] Because the nested design of thermal neutron detectors and ultrathermal neutron detectors strictly achieves the same source distance measurement, their flux ratio R can accurately reflect the uranium content of the formation and is not affected by the neutron moderation and absorption properties of the formation. Therefore, the uranium content can be directly calculated by converting the flux ratio of ultrathermal neutrons to thermal neutrons through a calibration coefficient, which is convenient and greatly improves the efficiency of uranium content calculation.

[0071] Example 6

[0072] This embodiment presents the application method of the co-located integrated dual neutron logging tool disclosed in Embodiment 4 above. The only difference from Embodiment 5 is that the hyperthermal neutron detector mentioned in step 2) is a second microstructure gas detector. When calibrating the thermal neutron detection efficiency in the same thermal neutron field, its outer wall surface is not provided with a second shielding moderation layer; the hyperthermal neutron to thermal neutron flux ratio R and the uranium content of the formation are also considered. P U The calculation process is the same, and will not be described again here.

[0073] 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 nested thermal neutron detector and an ultrathermal neutron detector; the thermal neutron detector has a through hole in the middle, and the detection part of the ultrathermal neutron detector is embedded in the through hole and forms an integral structure with the thermal neutron detector; The thermal neutron detector is configured as a first microstructure gas detector, which includes an annular chamber structure with an axial through hole, and the annular chamber structure is filled with ³He gas; a cathode drift electrode and an anode readout electrode are respectively provided at both ends of the annular chamber structure along its axial direction, and the cathode drift electrode and the anode readout electrode are respectively connected to the internal chamber of the annular chamber structure; The ultrathermal neutron detector includes a scintillation crystal, a photoelectric converter, and a first shielding and slowing layer. The scintillation crystal is a crystal sensitive to thermal neutrons. The photoelectric converter is coupled to the axial end face of any of the scintillation crystals, and the first shielding and slowing layer covers all the outer wall faces of the scintillation crystal. The axial direction of the scintillation crystal is defined to be parallel to the axial direction of the through-hole. The scintillation crystal and the first shielding and slowing layer constitute an ultrathermal neutron detection unit, which is embedded in the through-hole. The dimension of the ultrathermal neutron detection unit along the axial direction of the through-hole is adapted to the dimension of the through-hole along its axial direction. The thermal neutron detector and the ultrathermal neutron detector without a first shielding moderation layer are calibrated in the same thermal neutron field to calculate the ratio of their thermal neutron detection efficiencies, thereby determining the ratio of the thermal neutron detector's thermal neutron detection efficiency to the ultrathermal neutron detector's ultrathermal neutron detection efficiency.

2. The co-located dual neutron detector according to claim 1, characterized in that, The superthermal neutron detector includes a second microstructure gas detector and a second shielding moderation layer, wherein the second shielding moderation layer is disposed on all the outer wall surfaces of the second microstructure gas detector. The superthermal neutron detector is integrally embedded in the through hole, and its dimension along the axial direction of the through hole is adapted to the dimension of the through hole along its axial direction.

3. The co-located dual neutron detector according to claim 1, characterized in that, The dual neutron detector also includes a metal housing, which is enclosed and fitted over the outside of the thermal neutron detector and the ultrathermal neutron detector.

4. The co-located dual neutron detector according to claim 1, characterized in that, The 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.

5. A dual-neutron logging tool integrated in the same location, comprising a pulsed neutron source, a dual-neutron detector, a data acquisition and processing module, and a detector power supply for supplying power to the pulsed neutron source, the dual-neutron detector, and the 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 first signal processing channel, a second signal processing channel, an analog-to-digital converter, and an FPGA processor; The first and second signal processing channels have identical components, each including a preamplifier and a filter shaper connected in sequence. The input terminal of the preamplifier in the first signal processing channel is connected to the thermal neutron detector, and the output terminal is connected to the filter shaper of the first signal processing channel. The input terminal of the preamplifier in the second signal processing channel is connected to the ultrathermal neutron detector, and the output terminal is connected to the filter shaper of the second signal processing channel. The output terminals of the filter shapers are all connected to the analog-to-digital converter (ADC) for converting the detection signals from the thermal neutron detector and the ultrathermal neutron detector into digital signals, respectively. The output terminal of the ADC is connected to the FPGA processor, which is internally configured with a pulse counting module and a time spectrum analysis module for statistically analyzing the counting information of thermal neutrons and ultrathermal neutrons. The output of the FPGA processor is connected to the well logging computer via a communication connection, and is used to upload the counting information in order to calculate 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 thermal neutron detector and the ultrathermal neutron detector without a first or second shielding moderation layer are calibrated, and the ratio of their thermal neutron detection efficiencies is calculated to determine the ratio of the thermal neutron detector's thermal neutron detection efficiency to the ultrathermal neutron detector's ultrathermal neutron detection efficiency. The pulsed neutron source is activated to emit neutrons. The thermal neutron signal and the hyperthermal neutron signal are processed based on the first signal processing channel and the second signal processing channel, respectively. The thermal neutron time spectrum and the hyperthermal neutron time spectrum are collected. Based on the collected thermal neutron time spectrum and ultrathermal neutron time spectrum, the thermal neutron count and ultrathermal neutron count are counted respectively. Based on the ratio of the thermal neutron detector's thermal neutron detection efficiency to the ultrathermal neutron detector's ultrathermal neutron detection efficiency, and the statistical counts of thermal neutrons and ultrathermal neutrons, the flux ratio of ultrathermal 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 efficiency of the thermal neutron detector to that of the ultrathermal neutron detector without a first or second shielding moderation layer is equal to the ratio of the thermal neutron detector's thermal neutron detection efficiency to that of the ultrathermal neutron detector.

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