Magnetic flux detection sensor, position measurement system and casing coupling positioning method

Abstract

The invention discloses a magnetic flux detection sensor, a position measuring system and a casing coupling positioning method, and relates to the technical field of optical fiber logging, the magnetic flux detection sensor comprises a sensing optical fiber and two pairs of magnets and springs which abut against each other, and the sensing optical fiber penetrates through each pair of magnets and springs which abut against each other; each magnet is slidably connected with the sensing optical fiber in the direction of the sensing optical fiber, two gratings are arranged on the sensing optical fiber, the two springs are symmetrically distributed on the two sides of the center position between the two gratings, and the relative position between one end, close to the center position, of each spring and the center position is fixed; and each spring is closer to the central position than the abutted magnet. When the magnetic flux detection sensor provided by the invention passes through a casing coupling, the internal magnetic flux is obviously changed, the telescopic length of the spring is influenced by the permanent magnet, and the stress change of the spring is measured by using the grating, so that the detection of the coupling position is realized.

Description

Technical Field

[0001] This invention relates to the field of fiber optic logging technology, and in particular to a magnetic flux detection sensor, a position measurement system, and a method for locating casing couplings. Background Technology

[0002] Well logging depth signal analysis: Well logging depth is a crucial component of well logging information. All formation logging parameters correspond to depth; if the depth is incorrect, the logging information will lose its physical and geological significance. In cased well logging and perforation, electronic magnetic positioning sensors are commonly used to measure the position of the casing coupling to achieve depth correction.

[0003] Fiber optic sensing logging technology measures parameters such as temperature, pressure, displacement, and flow velocity throughout the wellbore via optical fibers. However, traditional electronic magnetic positioning instruments cannot be used due to the lack of circuitry. Currently, fiber optic logging commonly uses a magnetic positioning instrument with temperature storage attached to the lower end of the optical cable due to the lack of an effective means of optical detection casing coupling. This method cannot observe changes in downhole temperature and magnetic positioning in real time; the instrument must be removed to use the replay data for depth calibration, resulting in low logging efficiency. To achieve real-time depth calibration using the optical cable, a magnetic positioning instrument using fiber optic communication is needed. Currently, fiber optic sensors for measuring magnetic fields are based on magnetostrictive materials. Due to the small dynamic range of magnetostrictive materials (Terfenol-D terbium-dysprosium iron alloy), the use of a distributed feedback laser sensing structure to measure the minute strain of magnetostrictive materials offers high sensitivity. However, the sensor is significantly affected by vibration; interference signals generated by vibration during instrument deployment are difficult to distinguish from magnetic positioning signals, making accurate calibration of the fiber optic cable's deployment depth impossible. Summary of the Invention

[0004] The technical problem to be solved by this invention is to address the shortcomings of existing technologies. Specifically, it provides a positioning method for a magnetic flux detection sensor, a position measurement system, and a sleeve coupling, as detailed below:

[0005] 1) In a first aspect, the present invention provides a magnetic flux detection sensor, the specific technical solution of which is as follows:

[0006] It includes a sensing optical fiber and two pairs of abutting magnets and springs. The sensing optical fiber passes through each pair of abutting magnets and springs, and each magnet is slidably connected to the sensing optical fiber along the direction of the sensing optical fiber. The sensing optical fiber is provided with two gratings, and two springs are symmetrically distributed on both sides of the center position between the two gratings. The relative position between the end of each spring near the center position and the center position is fixed, and each spring is closer to the center position than the abutting magnet.

[0007] The beneficial effects of the magnetic flux detection sensor provided by this invention are as follows:

[0008] When a magnetic flux detection sensor passes through a sleeve coupling, the internal magnetic flux changes significantly. This change is influenced by a permanent magnet affecting the spring's extension and contraction length. A grating is used to measure the spring stress change, thus detecting the coupling's position. The magnetic flux detection sensor has a simple and reliable structure, a large spring strain, and is easy to measure. Furthermore, it can be easily connected in series with other fiber optic sensors, offering better economic efficiency and practicality.

[0009] Based on the above scheme, the magnetic flux detection sensor of the present invention can be further improved as follows.

[0010] Furthermore, it also includes two non-magnetic outer cylinders, each containing a pair of magnets and springs, with the other end of each spring abutting one end of the non-magnetic outer cylinder. The two non-magnetic outer cylinders are symmetrically distributed on both sides of the central position.

[0011] Furthermore, each non-magnetic outer cylinder has a locking ring at the other end, and each locking ring causes the magnet inside the non-magnetic outer cylinder to abut against the spring, and causes the spring to abut against the other end of the non-magnetic outer cylinder.

[0012] Furthermore, the two non-magnetic outer cylinders are fixedly connected to the sensing optical fiber using resin adhesive.

[0013] Furthermore, the two non-magnetic outer cylinders are integrated into one unit.

[0014] Furthermore, the two integrated non-magnetic outer cylinders have a glue injection hole in the middle. By injecting resin into the glue injection hole, the two non-magnetic outer cylinders are fixedly connected to the sensing optical fiber through the resin.

[0015] 2) In a second aspect, the present invention also provides a position measurement system based on fiber optic sensing, the specific technical solution of which is as follows:

[0016] The system includes a circulator, a photoelectric amplifier, a demultiplexer, an AD acquisition and signal processing unit, and a smart terminal, as well as any of the aforementioned magnetic flux detection sensors. The magnetic flux detection sensor, circulator, photoelectric amplifier, demultiplexer, AD acquisition and signal processing unit, and smart terminal are connected in sequence. When an optical pulse is transmitted through the circulator to the sensing optical fiber in the magnetic flux detection sensor, the reflected light generated by each grating is processed sequentially by the circulator, photoelectric amplifier, demultiplexer, and AD acquisition and signal processing unit to obtain the reflected wave information corresponding to each reflected light, which is then sent to the smart terminal. The smart terminal locates the magnetically conductive component based on the received reflected wave information.

[0017] Based on the above scheme, the position measurement system based on fiber optic sensing of the present invention can be further improved as follows.

[0018] Furthermore, it also includes a light source that emits pulsed light.

[0019] Furthermore, the magnetically conductive component is a sleeve coupling.

[0020] 3) In a third aspect, the present invention also provides a method for positioning a sleeve coupling, employing any of the aforementioned fiber optic sensing-based position measurement systems, the method comprising:

[0021] When the magnetic flux detection sensor moves along the well section, it emits light pulses in real time. When the real-time emitted light pulses are transmitted to the sensing optical fiber in the magnetic flux detection sensor through the circulator, the reflected light generated by each grating is processed by the circulator, photoelectric amplifier, wave demultiplexer, AD acquisition and signal processing unit in sequence to obtain the reflected wave information corresponding to each reflected light and send it to the smart terminal.

[0022] The intelligent terminal locates the casing coupling within the well section based on the received reflected wave information.

[0023] It should be noted that the beneficial effects of the technical solutions of the second and third aspects of the present invention and their corresponding possible implementations can be found in the above description of the technical effects of the first aspect and its corresponding possible implementations, and will not be repeated here. Attached Figure Description

[0024] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0025] Figure 1 This is a schematic diagram of the structure of a magnetic flux detection sensor according to an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of a position measurement system based on fiber optic sensing according to an embodiment of the present invention;

[0027] Figure 3 This is a schematic diagram illustrating the relationship between changes in grating wavelength and strain.

[0028] Figure 4 This is a schematic flowchart illustrating a method for positioning a sleeve coupling according to an embodiment of the present invention.

[0029] Figure 5 This is a schematic diagram of the testing principle.

[0030] The attached diagram lists the components represented by each number as follows:

[0031] 1. Sensor fiber optic;

[0032] 2. First grating;

[0033] 3. Second grating;

[0034] 4. The first magnet;

[0035] 5. The second magnet;

[0036] 6. First spring;

[0037] 7. The second spring;

[0038] 8. The first non-magnetic outer cylinder;

[0039] 9. Second non-magnetic outer cylinder;

[0040] 10. First locking ring;

[0041] 11. Second locking ring;

[0042] 12. Glue injection through hole;

[0043] 13. Light source;

[0044] 14. Circulator;

[0045] 15. Opto-amplifier;

[0046] 16. Wavelength divider;

[0047] 17. AD acquisition and signal processing unit;

[0048] 18. Smart terminals. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0050] like Figure 1 As shown, a magnetic flux detection sensor according to an embodiment of the present invention includes a sensing optical fiber 1 and two pairs of abutting magnets and springs. The sensing optical fiber 1 passes through each pair of abutting magnets and springs, and each magnet is slidably connected to the sensing optical fiber 1 along the direction of the sensing optical fiber 1. Two gratings are provided on the sensing optical fiber 1, and two springs are symmetrically distributed on both sides of the center position between the two gratings. The relative position between the end of each spring near the center position and the center position is fixed, and each spring is closer to the center position than the abutting magnet.

[0051] like Figure 1 As shown, a pair of abutting magnets and springs includes: a spring and a magnet abutting the spring; two pairs of abutting magnets and springs include: a first spring 6 and a first magnet 4 abutting, and a second spring 7 and a second magnet 5 abutting; two gratings provided on the sensing fiber 1 are divided into a first grating 2 and a second grating 3; the first spring 6 and the second spring 7 are symmetrically distributed on both sides of the center position between the two gratings; at this time, the first magnet 4 and the second magnet 5 are also symmetrically distributed on both sides of the center position between the two gratings.

[0052] Optionally, the above technical solution also includes two non-magnetic outer cylinders, each of which contains a pair of abutting magnets and springs, with the other end of each spring abutting one end of the non-magnetic outer cylinder, and the two non-magnetic outer cylinders symmetrically distributed on both sides of the central position.

[0053] The two non-magnetic outer cylinders are a first non-magnetic outer cylinder 8 and a second non-magnetic outer cylinder 9. A first spring 6 and a first magnet 4 are installed inside the first non-magnetic outer cylinder 8. The first magnet 4 abuts against one end of the first non-magnetic outer cylinder 8. A through hole is provided on the cylinder wall at this end so that the sensing optical fiber 1 can pass through. A second magnet 5 abuts against one end of the second non-magnetic outer cylinder 9. A through hole is also provided on the cylinder wall at this end so that the sensing optical fiber 1 can pass through.

[0054] Optionally, in the above technical solution, each non-magnetic outer cylinder is provided with a locking ring at the other end. Each locking ring causes the magnet inside the non-magnetic outer cylinder to abut against the spring, and causes the spring to abut against the other end of the non-magnetic outer cylinder.

[0055] The first non-magnetic outer cylinder 8 has a first locking ring 10 at one end, and the second non-magnetic outer cylinder 9 has a second locking ring 11 at the other end.

[0056] Optionally, in the above technical solution, the two non-magnetic outer cylinders are fixedly connected to the sensing optical fiber 1 by resin adhesive.

[0057] Optionally, in the above technical solution, the two non-magnetic outer cylinders are integrated into one unit.

[0058] Optionally, in the above technical solution, the two integrated non-magnetic outer cylinders are provided with a glue injection hole 12 in the middle. By injecting resin glue into the glue injection hole 12, the two non-magnetic outer cylinders are fixedly connected to the sensing optical fiber 1 through the resin glue.

[0059] When the first non-magnetic outer cylinder 8 and the second non-magnetic outer cylinder 9 are integrated, the assembly process of the magnetic flux detection sensor of the present invention is as follows:

[0060] 1) Install the first spring 6 and the first magnet 4 inside the first non-magnetic outer cylinder 8, and make the first spring 6 and the first magnet 4 abut against each other. The first magnet 4 abuts against one end of the first non-magnetic outer cylinder 8. Fix the first locking ring 10 to the other end of the first non-magnetic outer cylinder 8. Install the second spring 7 and the second magnet 5 inside the first non-magnetic outer cylinder 8, and make the second spring 7 and the second magnet 5 abut against each other. The second magnet 5 abuts against one end of the second non-magnetic outer cylinder 9. Fix the second locking ring 11 to the other end of the second non-magnetic outer cylinder 9.

[0061] 2) Two gratings, namely the first grating 2 and the second grating 3, are etched on the sensing fiber 1. Specifically, they can be configured as follows:

[0062] The center wavelengths of the first grating 2 and the second grating 3 differ by 10 nm, with a wavelength range between 1525 nm and 1565 nm. The distance between the first grating 2 and the second grating 3 is 60 mm. The first grating 2 and the second grating 3 can also be etched according to the actual situation.

[0063] 3) Through holes, i.e. central holes, are provided at the center positions of the first magnet 4, the second magnet 5, the first locking ring 10, the second locking ring 11, the first non-magnetic outer cylinder 8 which the first magnet 4 abuts against, and the second non-magnetic outer cylinder 9 which the second magnet 5 abuts against. The sensing optical fiber 1 passes through all the central holes and extends to the outside of the first locking ring 10 and the outside of the second locking ring 11. An injection through hole 12 is provided between the first non-magnetic outer cylinder 8 and the second non-magnetic outer cylinder 9.

[0064] 4) Inject high-temperature resin through the injection hole 12 and wait for the high-temperature resin to fully cure, so that the sensing fiber 1 is fixed to the first non-magnetic outer cylinder 8 and the second non-magnetic outer cylinder 9.

[0065] 5) After the high-temperature resin adhesive has completely cured, apply a tension of 1 to 2 N to one end of the sensing fiber 1 to straighten the sensing fiber 1. Inject the high-temperature resin adhesive into the center hole of the first magnet 4. After the high-temperature resin adhesive has completely cured, fix the first magnet 4 and the sensing fiber 1. Repeat the operation at the other end of the sensing fiber 1 to fix the second magnet 5 and the sensing fiber 1.

[0066] 6) Use a fiber optic grating demodulation device to measure the waveform and value of the first grating 2 of the sensing fiber 1 and whether the waveform and value of the first grating 2 are normal. After both are working normally, inject high-temperature resin glue into the threads of the first locking ring 10 and the second locking ring 11 and wait for the high-temperature resin glue to completely cure.

[0067] like Figure 2 As shown, an embodiment of the present invention provides a position measurement system based on fiber optic sensing, comprising a circulator 14, a photoelectric amplifier 15, a wave demultiplexer 16, an AD acquisition and signal processing unit 17, and a smart terminal 18, as well as any of the aforementioned magnetic flux detection sensors. The magnetic flux detection sensor, circulator 14, photoelectric amplifier 15, wave demultiplexer 16, AD acquisition and signal processing unit 17, and smart terminal 18 are connected in sequence. When an optical pulse is transmitted through the circulator 14 to the sensing optical fiber 1 in the magnetic flux detection sensor, the reflected light generated by each grating (i.e., each of the first grating 2 and the second grating 3) is processed sequentially by the circulator 14, photoelectric amplifier 15, wave demultiplexer 16, and AD acquisition and signal processing unit 17 to obtain the reflected wave information corresponding to each reflected light, which is then sent to the smart terminal 18. The smart terminal 18 positions the magnetically conductive component based on the received reflected wave information.

[0068] The following explanation uses the magnetically conductive component as the sleeve coupling:

[0069] The location of the casing coupling will cause a change in magnetic flux, resulting in a change in the grating data (center wavelength of the first grating 2 and the center wavelength of the second grating 3) of the sensing fiber optic cable 1. During the cable lowering process, the cable's depth can be measured by the surface system. At each depth point, the current depth can be obtained based on the grating data (i.e., reflected wave information, also known as reflected light signal) transmitted to the surface. When a casing coupling at a certain depth causes a change in the grating data, the acquisition software can record the change in the grating data at that depth, indicating the presence of a casing coupling at that location.

[0070] Optionally, the above technical solution also includes a light source 13, which emits pulsed light.

[0071] Optionally, in the above technical solution, the magnetic conductive component is a sleeve coupling.

[0072] In this system, the light source 13 and the circulator 14 are connected via optical fiber. The circulator 14 is connected to the sensing fiber 1 of the magnetic flux detection sensor via optical fiber. During measurement, the light source 13 emits light pulses. After passing through the circulator 14, the light pulses are transmitted to the first grating 2 and the second grating 3 of the magnetic flux detection sensor. When the light pulses pass through the first grating 2 and the second grating 3, they generate back-reflected light, respectively. The reflected light generated by the first grating 2 and the second grating 3 is transmitted to the photoelectric amplifier 15 after passing through the circulator 14. The photoelectric amplifier 15 converts the optical signal into an electrical signal and amplifies and filters the signal. After processing by the wavelength divider 16 and the AD acquisition and signal processing unit 17, the reflected wave information corresponding to each reflected light is obtained and sent to the intelligent terminal 18. The intelligent terminal 18 uses a signal processing algorithm to measure the wavelength of the fiber optic grating. The reflected wavelength of the fiber optic grating is affected by both temperature and stress, such as... Figure 3 As shown, specifically:

[0073] The relationship between wavelength change and strain change is characterized by the first formula, and the relationship between wavelength change and temperature change is characterized by the second formula. The first formula is... The second formula is Where, λ B λ represents the grating wavelength. B* Δε represents the changing wavelength of the grating, ΔT represents the change in strain, and ΔT represents the change in temperature.

[0074] To eliminate the influence of temperature on stress measurement, this invention employs two fiber gratings for measurement. In practical applications, the wavelengths of the two fiber gratings on the optical fiber are measured simultaneously in each measurement. Since the two fiber gratings are in the same temperature environment, the effect of temperature on the fiber grating wavelength is equal. The influence of temperature on wavelength can be eliminated by subtracting the wavelength values ​​of the two gratings.

[0075] Among them, the smart terminal 18 can be a computer or a smartphone, etc.

[0076] like Figure 4 As shown, an embodiment of the present invention provides a method for positioning a sleeve coupling, employing any of the aforementioned fiber optic sensing-based position measurement systems. The method includes:

[0077] S1. When the magnetic flux detection sensor moves along the well section, it emits light pulses in real time. When the light pulses emitted in real time are transmitted to the sensing fiber 1 in the magnetic flux detection sensor through the circulator 14, the reflected light generated by each grating is processed by the circulator 14, the photoelectric amplifier 15, the wave demultiplexer 16, and the AD acquisition and signal processing unit 17 in sequence to obtain the reflected wave information corresponding to each reflected light and send it to the smart terminal 18.

[0078] S2, the intelligent terminal 18 locates the casing coupling within the well section based on the received reflected wave information.

[0079] like Figure 5 As shown, when an external magnetically conductive component (such as a casing coupling) moves relative to the magnetic flux detection sensor in the direction indicated by the arrow (this can also be understood as the magnetic flux detection sensor moving along the well section, in which case the magnetic flux detection sensor moves relative to the casing coupling; in short, the magnetic flux detection sensor and the magnetically conductive component move relative to each other), when it reaches the first magnet 4, due to the attractive force of the first magnet 4, as the magnetically conductive component moves from position A to position B, the first magnet 4 will follow the magnetically conductive component to compress the first spring 6, causing a change in the stress of the first grating 2. At this time, the second grating 3 has no stress change. As the magnetically conductive component moves from position B to position C, the attractive force of the first magnet 4 gradually decreases, and the stress of the first grating 2 returns to its original value. At this time, the magnetically conductive component gradually approaches the second magnet 5. The second magnet 5 exerts an attractive force on the magnetically conductive component, thereby compressing the second spring 7. When a stress change occurs on the second grating 3, the magnetic force causes the second magnet 5 to compress the second spring 7, reducing the stress on the second grating 3. As the magnetically conductive component moves from position C to position D and gradually moves away from the second magnet 5, the stress value of the second grating 3 returns to its original value. Therefore, the measurement of the sleeve coupling can be achieved by measuring the wavelength change of the grating.

[0080] The magnetic flux detection sensor includes a sensing optical fiber 1 and two pairs of abutting magnets and springs. The sensing optical fiber 1 passes through each pair of abutting magnets and springs, and each magnet is slidably connected to the sensing optical fiber 1 along the direction of the sensing optical fiber 1. The sensing optical fiber 1 is provided with two gratings, and two springs are symmetrically distributed on both sides of the center position between the two gratings. The relative position between the end of each spring near the center position and the center position is fixed, and each spring is closer to the center position than the abutting magnet.

[0081] like Figure 1 As shown, a pair of abutting magnets and springs includes: a spring and a magnet abutting the spring; two pairs of abutting magnets and springs include: a first spring 6 and a first magnet 4 abutting, and a second spring 7 and a second magnet 5 abutting; two gratings provided on the sensing fiber 1 are divided into a first grating 2 and a second grating 3; the first spring 6 and the second spring 7 are symmetrically distributed on both sides of the center position between the two gratings; at this time, the first magnet 4 and the second magnet 5 are also symmetrically distributed on both sides of the center position between the two gratings.

[0082] Optionally, the above technical solution also includes two non-magnetic outer cylinders, each of which contains a pair of abutting magnets and springs, with the other end of each spring abutting one end of the non-magnetic outer cylinder, and the two non-magnetic outer cylinders symmetrically distributed on both sides of the central position.

[0083] The two non-magnetic outer cylinders are a first non-magnetic outer cylinder 8 and a second non-magnetic outer cylinder 9. A first spring 6 and a first magnet 4 are installed inside the first non-magnetic outer cylinder 8. The first magnet 4 abuts against one end of the first non-magnetic outer cylinder 8. A through hole is provided on the cylinder wall at this end so that the sensing optical fiber 1 can pass through. A second magnet 5 abuts against one end of the second non-magnetic outer cylinder 9. A through hole is also provided on the cylinder wall at this end so that the sensing optical fiber 1 can pass through.

[0084] Optionally, in the above technical solution, each non-magnetic outer cylinder is provided with a locking ring at the other end. Each locking ring causes the magnet inside the non-magnetic outer cylinder to abut against the spring, and causes the spring to abut against the other end of the non-magnetic outer cylinder.

[0085] The first non-magnetic outer cylinder 8 has a first locking ring 10 at one end, and the second non-magnetic outer cylinder 9 has a second locking ring 11 at the other end.

[0086] Optionally, in the above technical solution, the two non-magnetic outer cylinders are fixedly connected to the sensing optical fiber 1 by resin adhesive.

[0087] Optionally, in the above technical solution, the two non-magnetic outer cylinders are integrated into one unit.

[0088] Optionally, in the above technical solution, the two integrated non-magnetic outer cylinders are provided with a glue injection hole 12 in the middle. By injecting resin glue into the glue injection hole 12, the two non-magnetic outer cylinders are fixedly connected to the sensing optical fiber 1 through the resin glue.

[0089] When the first non-magnetic outer cylinder 8 and the second non-magnetic outer cylinder 9 are integrated, the assembly process of the magnetic flux detection sensor of the present invention is as follows:

[0090] 1) Install the first spring 6 and the first magnet 4 inside the first non-magnetic outer cylinder 8, and make the first spring 6 and the first magnet 4 abut against each other. The first magnet 4 abuts against one end of the first non-magnetic outer cylinder 8. Fix the first locking ring 10 to the other end of the first non-magnetic outer cylinder 8. Install the second spring 7 and the second magnet 5 inside the first non-magnetic outer cylinder 8, and make the second spring 7 and the second magnet 5 abut against each other. The second magnet 5 abuts against one end of the second non-magnetic outer cylinder 9. Fix the second locking ring 11 to the other end of the second non-magnetic outer cylinder 9.

[0091] 2) Two gratings, namely the first grating 2 and the second grating 3, are etched on the sensing fiber 1. Specifically, they can be configured as follows:

[0092] The center wavelengths of the first grating 2 and the second grating 3 differ by 10 nm, with a wavelength range between 1525 nm and 1565 nm. The distance between the first grating 2 and the second grating 3 is 60 mm. The first grating 2 and the second grating 3 can also be etched according to the actual situation.

[0093] 3) Through holes, i.e. central holes, are provided at the center positions of the first magnet 4, the second magnet 5, the first locking ring 10, the second locking ring 11, the first non-magnetic outer cylinder 8 which the first magnet 4 abuts against, and the second non-magnetic outer cylinder 9 which the second magnet 5 abuts against. The sensing optical fiber 1 passes through all the central holes and extends to the outside of the first locking ring 10 and the outside of the second locking ring 11. An injection through hole 12 is provided between the first non-magnetic outer cylinder 8 and the second non-magnetic outer cylinder 9.

[0094] 4) Inject high-temperature resin through the injection hole 12 and wait for the high-temperature resin to fully cure, so that the sensing fiber 1 is fixed to the first non-magnetic outer cylinder 8 and the second non-magnetic outer cylinder 9.

[0095] 5) After the high-temperature resin adhesive has completely cured, apply a tension of 1 to 2 N to one end of the sensing fiber 1 to straighten the sensing fiber 1. Inject the high-temperature resin adhesive into the center hole of the first magnet 4. After the high-temperature resin adhesive has completely cured, fix the first magnet 4 and the sensing fiber 1. Repeat the operation at the other end of the sensing fiber 1 to fix the second magnet 5 and the sensing fiber 1.

[0096] 6) Use a fiber optic grating demodulation device to measure the waveform and value of the first grating 2 of the sensing fiber 1 and whether the waveform and value of the first grating 2 are normal. After both are working normally, inject high-temperature resin glue into the threads of the first locking ring 10 and the second locking ring 11 and wait for the high-temperature resin glue to completely cure.

[0097] In this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0098] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0099] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A magnetic flux detection sensor, characterized in that, The device includes a sensing optical fiber and two pairs of abutting magnets and springs. The sensing optical fiber passes through each pair of abutting magnets and springs, and each magnet is slidably connected to the sensing optical fiber along the direction of the sensing optical fiber. The sensing optical fiber is provided with two gratings, and two springs are symmetrically distributed on both sides of the center position between the two gratings. The relative position between the end of each spring near the center position and the center position is fixed, and each spring is closer to the center position than the abutting magnet.

2. A magnetic flux detection sensor according to claim 1, characterized in that, It also includes two non-magnetic outer cylinders, each containing a pair of magnets and springs. The other end of each spring abuts against one end of the non-magnetic outer cylinder. The two non-magnetic outer cylinders are symmetrically distributed on both sides of the central position.

3. A magnetic flux detection sensor according to claim 2, characterized in that, Each non-magnetic outer cylinder has a locking ring at the other end. Each locking ring causes the magnet inside the non-magnetic outer cylinder to abut against the spring, and also causes the spring to abut against the other end of the non-magnetic outer cylinder.

4. The magnetic flux detection sensor according to claim 3, characterized in that, The two non-magnetic outer cylinders are fixedly connected to the sensing optical fiber by resin adhesive.

5. A magnetic flux detection sensor according to claim 4, characterized in that, The two non-magnetic outer cylinders are integrated into one unit.

6. A magnetic flux detection sensor according to claim 5, characterized in that, The two non-magnetic outer cylinders are integrated and have a glue injection hole in the middle. By injecting resin into the glue injection hole, the two non-magnetic outer cylinders are fixedly connected to the sensing optical fiber through the resin.

7. A position measurement system based on fiber optic sensing, characterized in that, The system includes a circulator, a photoelectric amplifier, a wavelength division multiplexer (WDM), an AD acquisition and signal processing unit, and a smart terminal, as well as a magnetic flux detection sensor according to any one of claims 1 to 6. The magnetic flux detection sensor, the circulator, the photoelectric amplifier, the WDM, the AD acquisition and signal processing unit, and the smart terminal are connected in sequence. When an optical pulse is transmitted through the circulator to the sensing optical fiber in the magnetic flux detection sensor, the reflected light generated by each grating is processed sequentially by the circulator, the photoelectric amplifier, the WDM, and the AD acquisition and signal processing unit to obtain the reflected wave information corresponding to each reflected light, which is then sent to the smart terminal. The smart terminal locates the magnetically conductive component based on the received reflected wave information.

8. A position measurement system based on fiber optic sensing according to claim 7, characterized in that, It also includes a light source that emits the pulsed light.

9. A position measurement system based on fiber optic sensing according to claim 7, characterized in that, The magnetically conductive component is a sleeve coupling.

10. A method for positioning a sleeve coupling, characterized in that, The method of using a position measurement system based on fiber optic sensing as described in any one of claims 7 to 9 includes: When the magnetic flux detection sensor moves along the well section, it emits light pulses in real time. When the emitted light pulses are transmitted to the sensing optical fiber in the magnetic flux detection sensor through the circulator, the reflected light generated by each grating is processed in sequence by the circulator, the photoelectric amplifier, the wave demultiplexer, and the AD acquisition and signal processing unit to obtain the reflected wave information corresponding to each reflected light, and then sent to the smart terminal. The intelligent terminal locates the casing coupling within the well section based on the received reflected wave information.

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