Variable-spacing dual-spacing logging instrument

Abstract

The invention discloses a source spacing variable double-source spacing logging instrument, and relates to the technical field of petroleum logging. The source spacing variable double-source spacing logging instrument comprises a radioactive source and a detector, a near probe, a far probe and an end frame set are installed in an instrument outer tube of the detector, and the distance between the near probe and the radioactive source is smaller than the distance between the far probe and the radioactive source so that gamma rays of different source spacing can be detected; the end frame group comprises a plurality of end frames, the plurality of end frames are sequentially connected between the near probe and the far probe, and the length of the end frame group is changed through the change of the number of the end frames; wherein the near probe is fixed in the instrument outer tube according to the source distance of the near probe, the far probe is connected with the end frame group, and the source distance of the far probe can be adjusted through the length change of the end frame group. According to the source-spacing-variable double-source-spacing logging instrument, after a fixed probe is provided as a basic value, a source-spacing-variable probe is provided, the optimal probe distance can be selected in different areas, and therefore the optimal data model is obtained.

Description

Technical Field

[0001] This application relates to the field of oil well logging technology, and in particular to a dual-source-spacing well logging instrument with variable source spacing. Background Technology

[0002] Neutron logging involves placing a downhole instrument equipped with a neutron source and detectors into the well. Fast neutrons emitted from the neutron source migrate outwards in a spherical pattern. As they penetrate the wellbore medium and enter the rock formation, the high-energy neutrons interact with the atomic nuclei of the matter, slowing them down. Their energy is continuously lost or weakened through diffusion and absorption. Two detectors with different source-to-detection distances are used to measure the ratio of the thermal neutron count rate, reflecting the rate at which the neutron density in the formation decays with increasing source-to-detection distance.

[0003] In practice, the inventors discovered the following problems with existing neutron logging instruments: the instrument is designed to operate in the tubing along with the neutron generator. The neutrons detected by the two He3 tubing thermal neutron detectors are emitted from the neutron generator and slowed down by the surrounding medium. Since the positions of the two detectors are fixed, the probe positions and spacing are also fixed. For different regions and formations, only fixed probes can be used for data acquisition, making it difficult to establish the best data interpretation model for one's own region. Summary of the Invention

[0004] The purpose of this application is to provide a dual-source-distance logging tool with variable source distance. In dual-source-distance logging, a fixed probe is provided as a baseline, and a variable-source-distance probe is provided. The optimal probe distance can be selected in different areas to obtain the best data model.

[0005] To achieve the above objectives, this application provides a variable source-spacing dual-source-spacing logging tool, including a radioactive source and a detector, wherein the detector includes an outer tube of the instrument;

[0006] The instrument's outer tube is equipped with a near probe and a far probe. The distance between the near probe and the radioactive source is smaller than the distance between the far probe and the radioactive source, so as to detect gamma rays at different source distances.

[0007] The instrument's outer tube is also equipped with an end frame assembly, which includes multiple end frames. These multiple end frames are connected sequentially between the near probe and the far probe. The length of the end frame assembly is varied by changing the number of end frames.

[0008] The near probe is fixed in the outer tube of the instrument according to the source distance of the near probe, and the far probe is connected to the end frame assembly. The source distance of the far probe is adjustable by changing the length of the end frame assembly.

[0009] In some embodiments, the end frames located at different positions between the near probe and the far probe have the same structure, the length of a single end frame in the direction of the distance between the near probe and the far probe is d, the number of end frames is n, the adjustable range D of the far probe source distance of the far probe is between 0 and nd, and each adjustment distance of the adjustable range D is an integer multiple of d.

[0010] In some embodiments, multiple end frames are nested sequentially between the near probe and the far probe to achieve dual axial and circumferential restraint between the multiple end frames.

[0011] In some embodiments, the end frames adjacent to the near probe and the far probe are nested together and fixedly connected as one unit by a plurality of fasteners.

[0012] In some embodiments, the length d of a single end mount in the direction of the distance between the near probe and the far probe is 2 cm, the number of end mounts n is 10, the adjustable range D of the far probe source distance of the far probe is between 0 and 20 cm, and each adjustment distance of the adjustable range D is an integer multiple of 2 cm.

[0013] In some embodiments, both the near probe and the far probe are gamma probes, the gamma probes comprising a NaI crystal and a photomultiplier tube, the NaI crystal being used to receive ambient gamma rays and generate scintillation light, and the photomultiplier tube being used to receive the scintillation light and ultimately generate a negative pulse signal.

[0014] In some embodiments, the gamma probe further includes a signal processing board, which is used to amplify and shape the raw signal electron beam acquired by the gamma probe to obtain a processable gamma signal.

[0015] In some embodiments, the gamma probe further includes an elastic buffer located on the same side of the NaI crystal and the photomultiplier tube, and between the photomultiplier tube and the signal processing board. The elastic buffer is used to press the photomultiplier tube and ensure good contact between the photomultiplier tube and the NaI crystal. The elastic buffer is also used to mitigate the vibration effects on the NaI crystal and the photomultiplier tube.

[0016] In some embodiments, the gamma probe further includes a shielding sleeve that wraps around the outer periphery of the NaI crystal and the photomultiplier tube, and the shielding sleeve is used to shield the NaI crystal and the photomultiplier tube from interference from external signals.

[0017] In some embodiments, the detector further includes a female connector and a shield located on the same side of the near probe and the far probe. The female connector is installed at the end of the instrument's outer tube and is used to connect to the male connector of the radioactive source. A mounting sleeve is installed on the outside of the female connector. The mounting sleeve is used to cover the seam between the radioactive source and the detector and to suppress the shaking of the radioactive source after the female connector is connected to the male connector of the radioactive source. The shield is installed inside the instrument's outer tube and is located between the radioactive source and the near probe. The shield is used to shield the neutrons and gamma rays emitted by the radioactive source directly towards the near probe and the far probe without passing through the strata.

[0018] Compared to the aforementioned background technology, the variable source-spacing dual-source-spacing logging tool provided in this application mainly includes a radioactive source and a detector. The detector includes an instrument outer tube. A near probe and a far probe are installed inside the instrument outer tube. The distance between the near probe and the radioactive source is smaller than the distance between the far probe and the radioactive source, so as to detect gamma rays with different source-spacings. An end-frame assembly is also installed inside the instrument outer tube. The end-frame assembly includes multiple end frames, which are connected sequentially between the near probe and the far probe. The length of the end-frame assembly is changed by varying the number of end frames. The near probe is fixed in the instrument outer tube according to the source-spacing of the near probe. The far probe is connected to the end-frame assembly. The source-spacing of the far probe is adjustable by varying the length of the end-frame assembly.

[0019] During the operation of this variable-spacing dual-spacing logging tool, a radioactive source and detector are lowered into the well. Neutrons are released into the formation through the radioactive source. As the neutrons pass through the wellbore medium and enter the rock formation, the high-energy neutrons interact with the atomic nuclei of the matter, slowing down, diffusing, and being absorbed. Their energy is continuously lost or weakened, and then the detector is used to detect the neutrons.

[0020] When the detector detects neutrons, because the instrument's outer tube contains near and far probes with varying distances from the radioactive source, it can detect gamma rays at different source distances. It's important to note that this variable-source-distance logging tool selects and fixes the optimal source distance for the near probe; that is, the near probe source distance is fixed. Furthermore, the far probe is connected to the end-frame assembly, and its source distance is adjustable by changing the length of the end-frame assembly. Therefore, the far probe source distance is adjustable.

[0021] When the length of the end frame assembly changes, since the end frame assembly consists of multiple end frames connected sequentially between the near probe and the far probe, the length of the end frame assembly can be changed by changing the number of end frames.

[0022] Based on the above structural and process descriptions, it can be seen that the variable source distance dual-source distance logging tool has at least the following beneficial effects: Based on the principle of dual-source distance logging, the variable source distance dual-source distance logging tool provides a fixed probe as a base value and then provides a probe with a variable source distance, which can select the optimal probe distance in different areas, thereby obtaining the best data model. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of a variable source-spacing dual-source-spacing logging tool provided in an embodiment of this application;

[0025] Figure 2 This application provides a signal principle diagram of a variable source-spacing dual-source-spacing logging tool.

[0026] Figure 3 This is a first part of the structural diagram of the variable source-spacing dual-source-spacing logging tool provided in the embodiments of this application;

[0027] Figure 4 This is a structural diagram of the second part of the variable source-spacing dual-source-spacing logging tool provided in the embodiments of this application;

[0028] Figure 5 A structural diagram of the third part of the variable source-spacing dual-source-spacing logging tool provided in the embodiments of this application;

[0029] Figure 6 A structural diagram of the fourth part of the variable source-spacing dual-source-spacing logging tool provided in the embodiments of this application;

[0030] Figure 7 The fifth structural diagram of the variable source-spacing dual-source-spacing logging tool provided in the embodiments of this application;

[0031] Figure 8 This is a sixth structural diagram of the variable source-spacing dual-source-spacing logging tool provided in the embodiments of this application.

[0032] in:

[0033] Detector 100

[0034] Instrument outer tube 101, near probe 102, near probe NaI crystal 1021, near probe photomultiplier tube 1022, near probe signal processing board 1023, near probe elastic buffer 1024, near probe shielding sleeve 1025, instrument bracket 1026, far probe 103, far probe shielding sleeve 1031, end frame assembly 104, end frame 1041, female connector 105, shielding body 106, connecting sleeve 107, high voltage module 108, first instrument frame 109, pressure block 110, second instrument frame 111, gamma signal board 112, first bushing 113, first socket 114, screw 115, second bushing 116, second socket 117, instrument housing metal connector 118. Detailed Implementation

[0035] In the explanation of relevant terms, gadolinium neutron logging tools are used in the field of oilfield logging. The measurement results of neutron gamma logging involve various stages of the interaction between neutrons and the formation, including fast neutron deceleration, thermal neutron diffusion, thermal neutron capture, and the generation, migration, and absorption of neutron gamma rays in the formation. The distance between the transmitting antenna and the receiving antenna in the logging instrument is called the source distance, which is the distance between the radiation source (neutron source or gamma source) and the midpoint of the detector in the radioactive logging instrument.

[0036] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] To address the problems existing in the prior art, the purpose of this application is to make the source distance of the far-end probe adjustable while the near-end probe is fixed, thereby solving the problem of the fixed distance between the two acquisition probes in the prior art. This overcomes the difficulty of using fixed probes for data acquisition in different regions and strata, making it difficult to establish the best data interpretation model based on the region. In this way, the application can establish the most ideal model by using the optimal source distance according to the geological structure of different regions.

[0039] Please refer to Figures 1 to 8 , Figure 1 This is a schematic diagram of the structure of the variable source-spacing dual-source-spacing logging tool provided in the embodiments of this application. Figure 2 This is a signal schematic diagram of a variable source-spacing dual-source-spacing logging tool provided in an embodiment of this application. Figure 3This is a structural diagram of the first part of the variable source-spacing dual-source-spacing logging tool provided in the embodiments of this application. Figure 4 This is a structural diagram of the second part of the variable source-spacing dual-source-spacing logging tool provided in the embodiments of this application. Figure 5 This is a structural diagram of the third part of the variable source-spacing dual-source-spacing logging tool provided in the embodiments of this application. Figure 6 This is a structural diagram of the fourth part of the variable source-spacing dual-source-spacing logging tool provided in the embodiments of this application. Figure 7 This is a fifth structural diagram of the variable source-spacing dual-source-spacing logging tool provided in the embodiments of this application. Figure 8 This is a sixth structural diagram of the variable source-spacing dual-source-spacing logging tool provided in the embodiments of this application.

[0040] In a first specific embodiment, the variable-source-distance logging tool provided in this application mainly includes a radioactive source and a detector 100. The detector 100 includes an instrument outer tube 101. A near probe 102 and a far probe 103 are installed inside the instrument outer tube 101. The distance between the near probe 102 and the radioactive source is smaller than the distance between the far probe 103 and the radioactive source, so as to detect gamma rays with different source distances. An end frame assembly 104 is also installed inside the instrument outer tube 101. The end frame assembly 104 includes multiple end frames 1041, which are connected sequentially between the near probe 102 and the far probe 103. The length of the end frame assembly 104 is changed by changing the number of end frames 1041. The near probe 102 is fixed in the instrument outer tube 101 according to the near probe source distance. The far probe 103 is connected to the end frame assembly 104. The source distance of the far probe 103 is adjustable by changing the length of the end frame assembly 104.

[0041] In this embodiment, the external pressure from the instrument is supported by the instrument outer tube 101. Optionally, the pressure resistance of the instrument outer tube 101 is 100 MPa.

[0042] During the operation of this variable-spacing dual-spacing logging tool, a radioactive source and detector 100 are lowered into the well. Neutrons are released into the formation through the radioactive source. As the neutrons pass through the wellbore medium and enter the rock formation, the high-energy neutrons interact with the atomic nuclei of the matter, slowing down, diffusing, and being absorbed, and their energy is continuously lost or weakened. The detector 100 then detects the neutrons.

[0043] When the detector 100 detects neutrons, because the instrument's outer tube 101 is equipped with a near probe 102 and a far probe 103, which are positioned at different distances from the radioactive source, gamma rays at different source distances can be detected. It is important to note that this variable-source-distance logging tool selects and fixes the optimal source distance for the near probe 102, meaning the near probe source distance is fixed. Furthermore, the far probe 103 is connected to the end frame assembly 104, and its source distance is adjustable by varying the length of the end frame assembly 104. Therefore, the far probe source distance is adjustable.

[0044] When the length of the end frame assembly 104 changes, since the end frame assembly 104 includes multiple end frames 1041 connected sequentially between the near probe 102 and the far probe 103, the length of the end frame assembly 104 can be changed by changing the number of end frames 1041.

[0045] Based on the above structural and process descriptions, it can be seen that the variable source distance dual-source distance logging tool has at least the following beneficial effects: Based on the principle of dual-source distance logging, the variable source distance dual-source distance logging tool provides a fixed probe as a base value and then provides a probe with a variable source distance, which can select the optimal probe distance in different areas, thereby obtaining the best data model.

[0046] The following explains the gadolinium neutron logging instrument and its working principle.

[0047] Neutron-formation interaction is the foundation of neutron and neutron-gamma logging methods. Neutrons interact with atomic nuclei as they pass through matter. Nuclear physics experiments show that different neutron energies result in different primary forms of reaction with the nuclei of various elements in the formation. Most neutrons entering the formation are fast or ultrafast neutrons, which are slowed down through various interactions, transforming from fast or ultrafast neutrons to slow neutrons.

[0048] In a homogeneous, infinitely large medium, the intensity of neutron gamma rays near the counter is related to the neutron source intensity and the source distance, including the following situations: ① The neutron gamma intensity decreases as the source distance increases; ② When the source distance is less than 35 cm, the neutron gamma intensity in dense formations is lower than that in porous formations; ③ When the source distance is greater than 35 cm, the neutron gamma intensity in water-rich porous formations is lower than that in water-poor dense formations; ④ If the neutron gamma intensity is the same for all hydrogen-containing formations at a certain source distance, then that point is the zero source distance, less than the zero source distance is the short source distance, and greater than the zero source distance is the long source distance. The choice of source distance can affect the neutron gamma value, and long source distances are generally used for neutron gamma logging. Under various formation simulation conditions, in a semi-logarithmic coordinate system, the captured gamma count has a linear relationship with the source distance, that is, the captured gamma count decreases exponentially with the increase of the source distance, but the gamma count rate is significantly smaller after the source distance exceeds 70 cm.

[0049] Due to their respective geological structures and formation fluids, the zero source distance and gamma decay index are affected differently in different oilfield blocks. The neutron gamma meter is mainly used to detect the radioactive intensity of secondary gamma rays from neutron sources. This instrument can change the length of the end-frame assembly 104 by adjusting the number of end-frames 1041, thereby changing the source distance. This allows for finding the most suitable source distance for different blocks, establishing their own interpretation templates, and thus improving the accuracy of neutron gamma interpretation.

[0050] In fact, the attenuation index is affected by factors such as formation structure and formation medium. Therefore, this technology designs a dual-source-spacing gadolinium neutron logging instrument with variable source spacing within a reasonable source spacing range. The purpose of this application is to improve the instrument's recognition rate by providing a fixed near probe 102 as a baseline and then providing a variable-spacing far probe 103. This allows for reasonable source spacing selection based on different geological blocks, obtaining optimal identification data, minimizing the influence of the surrounding environment on the data, and thus providing a more detailed understanding of the geological structure and oil and gas dynamics.

[0051] In some cases, this variable-spacing dual-spacing logging tool relates to the field of measurement technology and is a highly efficient logging method in geological exploration, oil and gas development, residual oil evaluation, and gas storage engineering detection logging.

[0052] In this variable-spacing dual-spacing logging tool, for the radioactive source, it is equivalent to using a fixed source for dual-spacing logging, which can maintain the stability of the source and ensure strong consistency of the data before and after. For the detector 100, it is equivalent to setting the source distance of the far probe 103 to be adjustable, so that the optimal probe distance can be selected in different areas to obtain the best data model. Through the near probe 102 and the far probe 103, it is equivalent to using a dual-spacing probe, which can obtain better comparison of data in the same formation, providing an additional layer of data assurance for data analysis.

[0053] In some cases, the workflow of this variable source-spacing dual-source-spacing logging tool is as follows.

[0054] The first step is to roughly estimate and select a suitable remote probe source distance for logging. The second step is to analyze and compare the data obtained by the near probe 102 and the remote probe 103. The third step is to determine whether the remote probe source distance needs to be adjusted based on the comparison results. If so, return to the first step; otherwise, proceed to the fourth step. The fourth step is to establish the best interpretation model based on the logging data for application in production.

[0055] In one specific implementation, please refer to [link / reference]. Figure 5The end frames 1041 located at different positions between the near probe 102 and the far probe 103 have the same structure. The length of a single end frame 1041 in the direction of the distance between the near probe 102 and the far probe 103 is d. The number of end frames 1041 is n. The adjustable range D of the far probe source distance of the far probe 103 is between 0 and nd, and the adjustment distance of the adjustable range D is an integer multiple of d each time.

[0056] Optionally, the multiple end frames 1041 are nested in stages between the near probe 102 and the far probe 103 to achieve dual axial and circumferential limiting between the multiple end frames 1041, thereby improving the structural reliability of the end frame assembly 104.

[0057] Based on this, the adjacent end frames 1041 between the near probe 102 and the far probe 103 are nested together and then fixedly connected as one unit by multiple fasteners.

[0058] For example, the length d of a single end frame 1041 in the direction of the distance between the near probe 102 and the far probe 103 is 2cm. The number n of end frames 1041 is 10, and each end frame 1041 is nested within each other and connected as a whole by three screws. The bottom end of the end frame assembly 104 is connected to the near probe 102, and the top end is connected to the far probe 103. By removing or adding end frames 1041, the length of the end frame assembly 104 can be changed, thereby changing the distance between the near probe 102 and the far probe 103. The end frame adjustment method in this embodiment achieves a wider range of adjustable distances and amplitudes. After selecting the optimal and reasonable near probe source distance of the near probe 102, the instrument is fixed. The removed end frame 1041 is installed on the top of the far probe 103 to fill the empty part of the instrument. Using this method, the adjustable range D of the far probe source distance of the far probe 103 can be between 0 and 20cm, and each adjustment distance of the adjustable range D is an integer multiple of 2cm.

[0059] It should be emphasized that in this embodiment, the near probe 102 is used as a fixed probe, which is the optimal source distance obtained through theoretical model deduction and actual logging data accumulation based on the principle of neutron gamma logging.

[0060] For the near probe 102, the advantages of using a fixed probe scheme are as follows.

[0061] First, the optimal neutron gamma logging curve can be obtained by theoretical modeling and accumulating a large amount of domestic and foreign logging data based on the near-probe source distance. Second, the near-probe logging curve can serve as a standard curve for other source distance neutron gamma curves as an important reference. Third, fixing the near-probe 102 is to prevent it from being moved easily, thus serving as a standard. Fourth, locking the near-probe 102 is to prevent accidental movement of it into the zero source distance range, thereby obtaining invalid data.

[0062] Based on this, this application also adopts an end-frame adjustment method, which allows the distance of the remote probe 103 to be adjusted significantly. The source distance of the remote probe can basically cover the effective source distance of neutron gamma logging through the end-frame adjustment.

[0063] In addition, the beneficial effects of the end frame adjustment method are explained below.

[0064] Each end frame 1041 has a length (equivalent to thickness) of 2cm, allowing for rapid calculation as needed. The distance between the near probe 102 and the far probe 103 can be quickly adjusted by moving the end frame 1041 without measurement. This design utilizes end frame adjustment, offering higher reliability, intuitiveness, safety, and stability during the adjustment process. Once adjusted, the source distance will not easily change. End frame adjustment also provides better memory, preventing unforeseen changes in the selected source distance during disassembly and maintenance by maintenance personnel, thus avoiding confusion in logging data due to unknown source distance changes. The end frame design is structurally simpler and effectively saves space, reducing the instrument diameter. Given that the neutron gamma logging tool is a small-diameter instrument, this design offers greater flexibility. Adjusting the source distance requires no movement of electronic components; only the far probe 103 and the end frame assembly 104 need to be moved together, making adjustment convenient and effectively avoiding electronic interference caused by probe movement.

[0065] In some cases, the variable-spacing dual-spacing gadolinium neutron logging instrument has two gamma probes that detect secondary gamma rays at different source spacings, and the source spacing of the gamma probes can be changed by altering the length of the end frame assembly 104.

[0066] A gamma sensor consists of a photomultiplier tube and a crystal. The photomultiplier tube is composed of a photocathode, an anode, dynodes, and a voltage divider circuit. When a scintillator receives radioactive radiation, it generates scintillation light. The scintillation light passes through the photocathode of the photomultiplier tube to generate photoelectrons. The photoelectrons are amplified by multiplication after passing through the dynodes, forming an electrical pulse signal at the anode. The count rate of this pulse signal reflects the intensity of radioactivity.

[0067] The two gamma signals are encoded by the communication circuit and then driven to the internal bus.

[0068] In some embodiments, both the near probe 102 and the far probe 103 are gamma probes. The gamma probe includes a NaI crystal and a photomultiplier tube. The photomultiplier tube consists of a photocathode, an anode, a dynode, and a voltage divider circuit. When ambient gamma rays enter the NaI crystal, the NaI crystal generates scintillation light. The scintillation light enters the photocathode of the photomultiplier tube, generating photoelectrons. The photoelectrons are multiplied step by step through the dynode, eventually generating a negative pulse signal at the anode.

[0069] In this embodiment, NaI crystal and photomultiplier tube are used as detection and acquisition tubes. The main purpose is to capture secondary gamma rays generated after neutron rays collide with the strata. It also has the characteristics of low cost.

[0070] like Figure 2 As shown, for the high-voltage module, the input is +12V provided by the power supply circuit, and the output is 1500-2000V high voltage. This high voltage is then adjusted by a voltage regulation circuit (RK2.868.438DL) to provide different high voltage levels for the two gamma probes. For charge amplification and threshold adjustment, the negative pulse signal output from the photomultiplier tube is amplified by a charge amplifier composed of operational amplifier N1A (QF2.868.117DL). The amplified signal is then compared by a voltage comparator circuit composed of N1B to identify pulse signals exceeding the threshold. The threshold can be adjusted by R6 and R7. For instrument power supply and bus communication, RK2.868.320DL is the power communication board, generating the instrument's internal power supplies of +12V, +3.3V, and +1.5V, and acquiring two gamma pulse signals, encoding them, and driving them to the internal bus.

[0071] like Figure 4 As shown, the near probe 102 includes a near probe NaI crystal 1021 and a near probe photomultiplier tube 1022. The near probe NaI crystal 1021 checks the intensity of gamma rays from the stratum and converts them into an electron beam; the near probe photomultiplier tube 1022 amplifies the electron beam converted from the near probe NaI crystal 1021 step by step so that the electronic circuit can detect the converted signal.

[0072] In some embodiments, the gamma probe further includes a signal processing board, which amplifies and shapes the raw signal electron beam acquired by the gamma probe to obtain a processable gamma signal.

[0073] like Figure 4 As shown, the near probe 102 also includes a near probe signal processing board 1023. The near probe signal processing board 1023 amplifies and shapes the raw signal electron beam acquired by the near probe 102 so that subsequent circuits can process the acquired gamma signal.

[0074] In addition, the near probe 102 also includes an instrument bracket 1026. The near probe signal processing board 1023 is fixedly mounted on the instrument bracket 1026.

[0075] In some embodiments, the gamma probe further includes an elastic buffer located on the same side of the NaI crystal and the photomultiplier tube, and between the photomultiplier tube and the signal processing board. The elastic buffer is used to press the photomultiplier tube and ensure good contact between the photomultiplier tube and the NaI crystal. The elastic buffer is also used to mitigate the vibration effects on the NaI crystal and the photomultiplier tube.

[0076] like Figure 4 As shown, the near probe 102 also includes a near probe elastic buffer 1024, which can be selected as a spring. The spring ensures good contact between the near probe NaI crystal 1021 and the near probe photomultiplier tube 1022, and can also effectively mitigate the strong shock waves generated by instrument vibration during logging, thereby protecting these two components from being easily broken.

[0077] In some embodiments, the gamma probe further includes a shielding sleeve that wraps around the NaI crystal and the photomultiplier tube, and the shielding sleeve is used to shield the NaI crystal and the photomultiplier tube from interference from external signals.

[0078] like Figure 4 As shown, the near probe 102 also includes a near probe shielding sleeve 1025. The near probe shielding sleeve 1025 eliminates interference from external magnetic fields and other signals to the near probe 102 during the acquisition and amplification of the original signal.

[0079] like Figure 6 As shown, the remote probe 103 also includes a remote probe NaI crystal, a remote probe photomultiplier tube, a remote probe signal processing board, a bracket, a spring, and a remote probe shielding sleeve 1031. The remote probe 103 is structurally similar to the near probe 102. For example, the remote probe shielding sleeve 1031 eliminates interference from external magnetic fields and other signals to the remote probe 103 during the acquisition and amplification of the original signal. This will not be elaborated further here.

[0080] In some embodiments, the detector 100 further includes a female connector 105 and a shield 106 located on the same side of the near probe 102 and the far probe 103.

[0081] like Figure 3 As shown, the female connector 105 is installed at the end of the instrument's outer tube 101. The female connector 105 is used to connect to the male connector of the radioactive source. A mounting sleeve 107 is installed on the outside of the female connector 105. After the radioactive source and the female connector 105 are connected, the mounting sleeve 107 can be rotated to cover the seam between the radioactive source and the detector 100. Then, it can be pulled down to suppress the shaking of the radioactive source, thereby ensuring the integrity of the radioactive source and the instrument.

[0082] It should be noted that the radioactive source involved in this case is an external source, and the source distance can be varied on the source rod depending on the dose intensity of different sources.

[0083] In addition, the shield 106 is installed inside the instrument's outer tube 101. The shield 106 is located between the radioactive source and the near probe 102. The shield 106 is used to shield the neutrons and gamma rays from the radioactive source that are directly directed at the near probe 102 and the far probe 103 without passing through the strata, which can reduce the interference of the radioactive source on the measurement results.

[0084] like Figure 7 As shown, the high-voltage module 108 provides high voltage to the near-probe photomultiplier tube 1022 and the far-probe photomultiplier tube. The first instrument frame 109 is used to place the instrument circuit board, and the pressure block 110 is used to suppress the movement of the internal components of the instrument to ensure the stability of the instrument performance. The second instrument frame 111 is used to place the gamma signal circuit board, and the gamma signal board 112 is used to process the signal after the probe is acquired, and to shape, count and convert the signal so that the logging software can recognize and process it.

[0085] like Figure 8 As shown, the first bushing 113 is used to protect the insulation between the pin and the housing, the first socket 114 is used to pass the wire pin, the screw 115 is used to connect the instrument head pin, the second bushing 116 is used to protect the insulation between the pin and the housing, the second socket 117 is used to connect with other instrument wires, and the instrument housing metal connector 118 is used to connect in series with other instruments.

[0086] In summary, this variable source-spacing dual-source-spacing logging tool adopts a variable source-spacing structure design, which has at least the following advantages: the radioactive source is a fixed source, ensuring radioactivity stability; the adjustable source-spacing allows for the establishment of the most ideal model in different regions based on their geological structures; the adjustable source-spacing range is relatively wide, basically covering the optimal effective source-spacing range; and the source-spacing adjustment is convenient and simple, requiring no wire disconnection and not affecting the instrument's structural performance.

[0087] It should be noted that many of the components mentioned in this application are general standard parts or components known to those skilled in the art, and their structure and principle can be learned by those skilled in the art through technical manuals or through conventional experimental methods.

[0088] It should be noted that in this specification, relational terms such as first and second are used only to distinguish one entity from several other entities, and do not necessarily require or imply any such actual relationship or order between these entities.

[0089] The above provides a detailed description of the variable source-spacing dual-source-spacing logging tool provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this application. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A variable-source-spacing dual-source-spacing logging tool, comprising a radioactive source and a detector, characterized in that, The detector includes an outer tube; The instrument's outer tube is equipped with a near probe and a far probe. The distance between the near probe and the radioactive source is smaller than the distance between the far probe and the radioactive source, so as to detect gamma rays at different source distances. The instrument's outer tube is also equipped with an end frame assembly, which includes multiple end frames. These multiple end frames are connected sequentially between the near probe and the far probe. The length of the end frame assembly is varied by changing the number of end frames. The near probe is fixed in the outer tube of the instrument according to the source distance of the near probe, and the far probe is connected to the end frame assembly. The source distance of the far probe is adjustable by changing the length of the end frame assembly.

2. The variable source spacing dual source spacing logging tool according to claim 1, characterized in that, The end frames located at different positions between the near probe and the far probe have the same structure. The length of a single end frame in the direction of the distance between the near probe and the far probe is d. The number of end frames is n. The adjustable range D of the far probe source distance of the far probe is between 0 and nd, and each adjustment distance of the adjustable range D is an integer multiple of d.

3. The variable source spacing dual source spacing logging tool according to claim 1, characterized in that, The multiple end frames are nested sequentially between the near probe and the far probe to achieve dual axial and circumferential limiting among the multiple end frames.

4. The variable source spacing dual source spacing logging tool according to claim 3, characterized in that, The end frames adjacent to the near probe and the far probe are nested together and fixedly connected as one unit by multiple fasteners.

5. The variable source spacing dual source spacing logging tool according to claim 2, characterized in that, The length d of a single end mount in the direction of the distance between the near probe and the far probe is 2cm, the number of end mounts n is 10, the adjustable range D of the far probe source distance is between 0 and 20cm, and each adjustment distance of the adjustable range D is an integer multiple of 2cm.

6. The variable source spacing dual source spacing logging tool according to claim 1, characterized in that, Both the near probe and the far probe are gamma probes. The gamma probe includes a NaI crystal and a photomultiplier tube. The NaI crystal is used to receive ambient gamma rays and generate scintillation light, and the photomultiplier tube is used to receive the scintillation light and ultimately generate a negative pulse signal.

7. The variable source spacing dual source spacing logging tool according to claim 6, characterized in that, The gamma probe also includes a signal processing board, which is used to amplify and shape the raw signal electron beam acquired by the gamma probe to obtain a processable gamma signal.

8. The variable source spacing dual source spacing logging tool according to claim 7, characterized in that, The gamma probe also includes an elastic buffer, which is located on the same side of the NaI crystal and the photomultiplier tube, and between the photomultiplier tube and the signal processing board. The elastic buffer is used to press the photomultiplier tube and ensure good contact between the photomultiplier tube and the NaI crystal. The elastic buffer is also used to mitigate the vibration effects on the NaI crystal and the photomultiplier tube.

9. The variable source spacing dual source spacing logging tool according to claim 6, characterized in that, The gamma probe also includes a shielding sleeve, which wraps around the outer periphery of the NaI crystal and the photomultiplier tube. The shielding sleeve is used to shield the NaI crystal and the photomultiplier tube from interference from external signals.

10. The variable source spacing dual source spacing logging tool according to claim 1, characterized in that, The detector also includes a female connector and a shield located on the same side of the near probe and the far probe. The female connector is installed at the end of the instrument's outer tube and is used to connect to the male connector of the radioactive source. A connecting sleeve is installed on the outside of the female connector. The connecting sleeve is used to cover the seam between the radioactive source and the detector and to suppress the shaking of the radioactive source after the female connector is connected to the male connector of the radioactive source. The shield is installed inside the instrument's outer tube and is located between the radioactive source and the near probe. The shield is used to shield the neutrons and gamma rays emitted by the radioactive source directly towards the near probe and the far probe without passing through the strata.

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