Magnetic descaling device for borehole operation

Abstract

The invention relates to a magnetic descaling device for downhole operation, relates to the technical field of petrochemical engineering, and is used for descaling liquid in a shaft in the petroleum industry. The descaling device comprises an upper connector, a screen pipe, a central base pipe, an outer cylinder and a lower connector. After liquid in a well enters the descaling device through the lower connector, viscous liquid flows slowly, enters the central base pipe along the lower end of the central base pipe, passes through the screen pipe and is divided into small liquid particles, the overall viscosity is reduced, and the viscous liquid enters a production pipe column along with the liquid. The liquid with small viscosity flows fast, flows in through the annular space of the central base tube and the outer cylinder after being shunted from the bottom, and enters a production pipe column through the inner circulation hole and the hole in the upper portion of the screen tube. The magnet outside the central base tube generates magnetic lines to radiate in the descaling device, liquid flowing through the descaling device is magnetized, the paraffin crystallization pattern is destroyed, and the paraffin precipitation speed is reduced. The magnet and the central base tube have high magnetism and can adsorb iron oxide chips and mineral impurities, and a good descaling effect is achieved.

Description

[0001] The present invention claims priority to Chinese patent application CN202410332581.2, filed on March 22, 2024, entitled “Magnetic descaling device for downhole operations”, and the entire contents of the above application are incorporated herein by reference. Technical Field

[0002] The present invention relates to the technical field of petrochemical industry, in particular to a magnetic descaling device for underground operation. Background Art

[0003] As oilfield development continues, the water content in oil wells gradually increases, wax deposition becomes increasingly serious, the viscosity of the well fluid increases, and production becomes difficult; after long-term production, the inner wall of the casing in the well is corroded and oxidized by the well fluid, generating rust, causing serious scaling of the production tubing and clogging the suction port; impurities are deposited at the pump seat of the oil pump, causing the production tubing to lose its sealing performance and unable to produce normally, which directly affects the normal development of the oilfield.

[0004] There are many magnetic descaling devices in the prior art, but there is little disclosure on magnetic descaling in wellbores of the oil industry.

[0005] CN201310157623.5 Rare earth high-efficiency strong magnetic anti-scaling device relates to a rare earth high-efficiency strong magnetic anti-scaling device, which is installed on the pipeline in front of the pump body to form a strong magnetic field on the cross section of the pipeline; the pressurizer is formed with a plurality of diversion holes which are not on the same plane as the central axis of the pipeline, and the diversion holes are inclined in the same direction at a certain angle around the central axis of the pipeline; the fluid output from the pressurizer enters the pipeline provided with a rare earth strong magnetic array in a multi-strand spiral ascending manner, and is magnetized by the strong magnetic field formed thereby, thereby causing changes in physical properties; the device has an obvious effect on stratum mineral elements, but has a poor effect on metal impurities such as rust.

[0006] CN200920280785.7 Strong magnetic anti-wax and anti-scale device, the utility model is installed on the oil gathering pipeline at the outlet of the oil well or on the water injection pipeline of a single well in the water injection distribution room. It can effectively prevent the oil gathering pipeline or the water injection pipeline from wax and scale formation during the oil production process or the water injection process; the device cannot be lowered into the well with the pipe string and cannot achieve scale prevention in the wellbore.

[0007] CN201020105769.7 Multifunctional strong magnetic anti-scaling, dewaxing and oil-increasing device. The utility model discloses a multifunctional strong magnetic anti-scaling, dewaxing and oil-increasing device, which includes a lower anti-scaling, dewaxing and oil-increasing device and one or more upper anti-scaling, dewaxing and oil-increasing devices. The upper anti-scaling, dewaxing and oil-increasing device is installed at the upper end of the oil pipe of the oil pump, and the lower anti-scaling, dewaxing and oil-increasing device is installed between the lower end of the oil pump and the valve seat. The device is suitable for tubular pumps or plunger pumps, but not for submersible electric pumps. Summary of the Invention

[0008] The invention provides a magnetic descaling device for downhole operation, which is used for descaling liquid in a wellbore of the petroleum industry and improves the descaling effect of the liquid in the wellbore.

[0009] The present invention provides a magnetic descaling device for underground operations, comprising an upper joint, a screen pipe, a central base pipe, an outer cylinder and a lower joint; the upper joint has a first central hole, the lower joint has a second central hole, the upper joint and the lower joint are respectively connected to the two ends of the outer cylinder, the first central hole and the second central hole are connected through the cavity of the outer cylinder; the screen pipe is arranged in the cavity of the outer cylinder, one end of the screen pipe is open and the other end is closed, the open end of the screen pipe is connected to the upper joint, the opening of the screen pipe is connected to the first central hole; the closed end of the screen pipe a gap is left between the end and the lower joint; the central base pipe is arranged between the outer cylinder and the screen pipe, and a first annular gap is formed between the inner wall of the central base pipe and the outer wall of the screen pipe; the first annular gap is connected to the external space of the central base pipe through the inner circulation hole at one end close to the upper joint; the central base pipe is open at both ends, one end of the central base pipe is connected to the upper joint, and a gap is left between the other end and the lower joint; a plurality of groups of first magnets are installed on the outer surface of the central base pipe, and the plurality of groups of first magnets are arranged at intervals along the axial direction of the central base pipe.

[0010] During use, the descaling device is connected to the downhole tubing. After the liquid in the well enters the interior of the descaling device through the second center hole of the lower joint, the viscous liquid flows slowly along the lower end of the center base pipe into the center base pipe. After passing through the screen pipe, it is divided into smaller liquid particles, reducing the overall viscosity, and then enters the production tubing with the fluid. The liquid with lower viscosity flows faster, and after being diverted at the bottom, it flows through the annular space between the center base pipe and the outer cylinder, and enters the production tubing through the inner circulation hole and the upper hole of the screen pipe. The first magnet on the outside of the center base pipe generates magnetic lines of force that radiate inside the descaling device, magnetizing the liquid flowing through the inside of the descaling device, destroying the paraffin crystallization pattern, and slowing down the wax deposition rate. The first magnet and the center base pipe have high magnetic properties and can absorb iron oxide chips and mineral impurities, achieving a good descaling effect.

[0011] In one embodiment, a strong magnetic base tube is further provided between the outer tube and the central base tube, with both ends of the strong magnetic base tube being open and connected to the upper joint and the lower joint respectively; a second annular gap is formed between the inner wall of the strong magnetic base tube and the outer wall of the central base tube, an end of the second annular gap close to the upper joint is connected to the first annular gap through the inner circulation hole, and an end of the second annular gap close to the lower joint is connected to the second center hole; a plurality of groups of second magnets are mounted on the outer surface of the strong magnetic base tube, and the plurality of groups of second magnets are arranged at intervals along the axial direction of the strong magnetic base tube.

[0012] In one embodiment, a spiral groove is formed on the outer surface of the ferromagnetic substrate tube, and the second magnet is installed in the spiral groove.

[0013] In one embodiment, a flexible steel wire is further provided on the strong magnetic base tube, one end of the flexible steel wire is fixed on the strong magnetic base tube, and the other end extends into the second annular gap.

[0014] In one embodiment, the flexible steel wires and the first magnets are distributed in a staggered manner.

[0015] In one embodiment, a third annular gap is formed between the outer wall of the ferromagnetic substrate tube and the inner wall of the outer cylinder, and external circulation holes are opened at both ends of the outer cylinder, and the external circulation holes are used to connect the third annular gap with the external space of the outer cylinder.

[0016] In one embodiment, a magnetic shield is provided on the outer cylinder.

[0017] In one embodiment, the upper end of the upper joint is used to connect the downhole tubing string, and the lower end of the upper joint is provided with a first annular protrusion and a second annular protrusion around the first center hole, the first annular protrusion is located on the inner side of the second annular protrusion, and the inner circulation hole is provided on the first annular protrusion; the screen pipe is connected to the internal thread of the first center hole by an external thread provided at its upper end; the central base pipe is connected to the internal thread on the first annular protrusion by an external thread provided at its upper end; the strong magnetic base pipe is connected to the internal thread on the second annular protrusion by an external thread provided at its upper end; the outer tube is connected to the external thread on the second annular protrusion by an internal thread provided at its upper end; the upper end of the lower joint is provided with a third annular protrusion, and the strong magnetic base pipe is connected to the internal thread on the third annular protrusion by an external thread provided at its lower end.

[0018] In one embodiment, the central base pipe and the strong magnetic base pipe are made of steel.

[0019] In one embodiment, the outer wall of the screen tube is wrapped with several layers of filter screens to form a filter screen tube.

[0020] Compared with the prior art, the advantage of the present invention is that after the liquid in the well enters the interior of the descaling device through the second center hole of the lower joint, the viscous liquid flows slowly, enters the center base pipe along the lower end of the center base pipe, and is divided into smaller liquid particles after passing through the screen pipe, reducing the overall viscosity, and enters the production tubing with the fluid. When the liquid with lower viscosity passes through the second annular gap between the center base pipe and the strong magnetic base pipe, the small annular volume produces a pressurization effect, the liquid flow rate increases, and drives the flexible steel wire on the strong magnetic base pipe to vibrate frequently; the frequently vibrating flexible steel wire can cut off the magnetic lines of force, enhance the internal magnetic field strength, and is more conducive to destroying the paraffin crystallization pattern and slowing down the wax deposition rate. The flexible steel wire and the first magnet are staggered in distribution correspondingly, and the magnet is located on the upper part of the flexible steel wire to generate an upward suction force on the flexible steel wire. A second magnet is installed within a spiral groove on the outer surface of the strong magnetic base pipe, creating a highly magnetic spiral field. This, in conjunction with the first magnet on the central base pipe, generates magnetic lines of force that radiate within the descaling device. This further enhances the internal radiation, magnetizing the fluid flowing through it and disrupting the paraffin wax crystallization pattern, thereby slowing wax deposition. The central and strong magnetic base pipes are made of steel. Due to the magnetic lines of force radiating from the magnets, the strong magnetic base pipes and central base pipes possess a high degree of magnetism, attracting iron oxide and other mineral impurities. A magnetic shield is installed within the outer barrel to block the magnetic lines of force and prevent them from radiating into the wellbore casing. Fluid in the annulus of the wellbore enters through the external circulation port at the bottom of the outer barrel and exits through the external circulation port at the top. Iron oxide and other mineral impurities are attracted by the second magnet and strong magnetic base pipe, while non-ferromagnetic impurities are trapped within the cavity between the strong magnetic base pipe and the outer barrel, achieving the desired descaling effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Hereinafter, the present invention will be described in more detail based on embodiments with reference to the accompanying drawings.

[0022] Figure 1 It is a structural schematic diagram of the magnetic descaling device for underground operations of the present invention.

[0023] Reference numerals:

[0024] 1. Upper joint; 2. Screen tube; 3. Central base pipe; 4. First magnet; 5. Inner circulation hole; 6. Strong magnetic base pipe; 7. Flexible steel wire; 8. Second magnet; 9. Outer cylinder; 10. Magnetic shield; 11. Outer circulation hole; 12. Lower joint; 13. First annular protrusion; 14. Second annular protrusion; 15. Third annular protrusion; 16. First annular gap; 17. Second annular gap; 18. Third annular gap; 19. First center hole; 20. Second center hole. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below.

[0026] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0027] The words "first", "second" and similar terms used in this disclosure are for descriptive purposes only and do not indicate any order, quantity or importance, but are only used to distinguish different parts. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "multiple" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined. Words such as "include" or "comprise" mean that the elements before the word include the elements listed after the word, and do not exclude the possibility of covering other elements. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0028] In the present disclosure, when a specific device is described as being located between a first device and a second device, an intervening device may or may not be present between the specific device and the first device or the second device. When a specific device is described as being connected to another device, the specific device may be directly connected to the other device without an intervening device, or may be not directly connected to the other device but with an intervening device.

[0029] All terms (including technical or scientific terms) used in this disclosure have the same meaning as those understood by one of ordinary skill in the art to which this disclosure belongs, unless otherwise specifically defined. It should also be understood that terms defined in, for example, general dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an idealized or highly formal sense, unless explicitly defined herein.

[0030] like Figure 1As shown, the magnetic descaling device for underground operations provided by the present invention (hereinafter referred to as the descaling device) is mainly composed of an upper joint 1, a screen tube 2, a central base pipe 3, an outer tube 9 and a lower joint 12. The upper joint 1 and the lower joint 12 are respectively connected to the two ends of the outer tube 9, and the three together form the shell of the descaling device. The descaling device is connected to the downhole tubing string through the upper joint 1 and the lower joint 12. A first center hole 19 is provided on the upper joint 1, and a second center hole 20 is provided on the lower joint 12. The first center hole 19 and the second center hole 20 are connected through the cavity of the outer tube 9. Several holes are evenly distributed on the screen tube 2 that pass through the inside and outside of the screen tube 2. The screen tube 2 is arranged in the cavity of the outer tube 9. One end of the screen tube 2 is open and the other end is closed. The open end of the screen tube 2 is connected to the upper joint 1, and the opening of the screen tube 2 is connected to the first center hole 19; a gap is left between the closed end of the screen tube 2 and the lower joint 12. The central base pipe 3 is disposed between the outer cylinder 9 and the screen tube 2. A first annular gap 16 is formed between the inner wall of the central base pipe 3 and the outer wall of the screen tube 2. A gap is also left between the outer wall of the central base pipe 3 and the inner wall of the outer cylinder 9, forming an annular space. The end of the first annular gap 16, closest to the upper connector 1, communicates with the annular space outside the central base pipe 3 through the internal circulation hole 5. The central base pipe 3 is open at both ends, with one end connected to the upper connector 1 and the other end separated from the lower connector 12 by a gap. Multiple sets of first magnets 4 are mounted on the outer surface of the central base pipe 3, spaced apart along the axial direction of the central base pipe 3. Preferably, the central base pipe 3 is made of steel. Due to the influence of the magnetic field lines of the magnets, the central base pipe 3 has a high magnetic property, capable of attracting iron oxide chips and mineral impurities.

[0031] When in use, the descaling device is connected to the downhole tubing. After the liquid in the well enters the interior of the descaling device through the second center hole 20 of the lower joint 12, the viscous liquid flows slowly along the lower end of the center base pipe 3 into the center base pipe 3. After passing through the screen pipe 2, it is divided into smaller liquid particles, reducing the overall viscosity, and enters the production tubing with the fluid. The liquid with lower viscosity flows faster, flows through the annular space between the center base pipe 3 and the outer cylinder 9 after being diverted at the bottom, and enters the production tubing through the inner circulation hole 5 and the upper hole of the screen pipe 2. The first magnet 4 outside the center base pipe 3 generates magnetic lines of force that radiate inside the descaling device, magnetizing the liquid flowing through the inside of the descaling device, destroying the paraffin crystallization pattern, and slowing down the wax deposition rate. The first magnet 4 and the center base pipe 3 have high magnetism and can absorb iron oxide chips and mineral impurities to achieve a descaling effect. The descaling device can be connected to the lowest end of the tubing string, and can also be used in conjunction with other tools.

[0032] In order to improve the separation effect of the screen tube 2 on the viscous liquid, in some embodiments, preferably, several layers of filter screen are wrapped around the outer wall of the screen tube 2 to form a filter screen tube. The filter screen tube can separate the viscous liquid into smaller liquid particles, further reduce the overall viscosity, increase the liquid flow rate, and reduce scaling.

[0033] In some embodiments, a strong magnetic base tube 6 is further provided between the outer tube 9 and the central base tube 3. The strong magnetic base tube 6 is open at both ends. The upper end of the strong magnetic base tube 6 is connected to the upper joint 1, and the lower end of the strong magnetic base tube 6 is connected to the lower joint 12. A second annular gap 17 is formed between the inner wall of the strong magnetic base tube 6 and the outer wall of the central base tube 3. The second annular gap 17 is connected to the first annular gap 16 through the inner circulation hole 5; the end of the second annular gap 17 near the lower joint 12 is connected to the second central hole 20. A third annular gap 18 is formed between the outer wall of the strong magnetic base tube 6 and the inner wall of the outer tube 9. The outer tube 9 is provided with an outer circulation hole 11 at both ends. The third annular gap 18 is connected to the external space of the outer tube 9 through the outer circulation hole 11. Multiple groups of second magnets 8 are installed on the outer surface of the strong magnetic base tube 6. The multiple groups of second magnets 8 are arranged at intervals along the axial direction of the strong magnetic base tube 6. The second magnets 8 are preferably high-strength magnets with very high magnetic force. Further preferably, the strong magnetic base pipe 6 is made of steel material and is affected by the radiation of the magnetic lines of force of the magnet. The strong magnetic base pipe 6 has a high magnetism and can absorb iron oxide chips and mineral impurities. The second magnet 8 on the strong magnetic base pipe 6 and the first magnet 4 on the central base pipe 3 work together to generate magnetic lines of force that radiate inside the descaling device, further enhancing the radiation inside the descaling device, magnetizing the liquid flowing through the inside, enhancing the destruction of the paraffin crystal structure, and helping to slow down the wax deposition rate. The annular space liquid in the wellbore can enter the third annular gap 18 from the outer circulation hole 11 at the lower part of the outer cylinder 9, and then flow out through the outer circulation hole 11 at the upper part of the outer cylinder 9. When the liquid flows through the third annular gap 18, substances such as iron oxide chips and mineral impurities in the liquid can be adsorbed by the second magnet 8 and the strong magnetic base pipe 6, and non-ferromagnetic impurities can be stored in the third annular gap 18 between the strong magnetic base pipe 6 and the outer cylinder 9.

[0034] Further preferably, a spiral groove is opened on the outer surface of the strong magnetic base tube 6, and the second magnet 8 is installed in the spiral groove to form a spiral magnetic field with very high magnetic force, which is conducive to the installation of the second magnet 8 and its magnetic field distribution is relatively more uniform in space.

[0035] In some embodiments, a flexible steel wire 7 is further provided on the strong magnetic base pipe 6, with one end of the flexible steel wire 7 fixed to the strong magnetic base pipe 6 and the other end extending into the second annular gap 17 between the central base pipe 3 and the strong magnetic base pipe 6. Preferably, the flexible steel wire 7 and the first magnet 4 are arranged in a staggered manner, with the magnet located above the flexible steel wire 7 to exert an upward suction force on the flexible steel wire 7. When a liquid with low viscosity passes through the second annular gap 17 between the central base pipe 3 and the strong magnetic base pipe 6, the small annular volume creates a pressurization effect, which increases the liquid flow rate and causes the flexible steel wire 7 on the strong magnetic base pipe 6 to vibrate frequently. The frequently vibrating flexible steel wire 7 can cut off the magnetic lines of force, enhance the internal magnetic field strength, and further facilitate the destruction of the paraffin crystallization pattern and slow down the wax deposition rate.

[0036] In some embodiments, a magnetic shield 10 is installed on the outer cylinder 9, specifically inside the outer cylinder 9. The magnetic shield 10 can block the magnetic lines of force to prevent radiation from reaching the casing in the well.

[0037] In some embodiments, the upper and lower ends of the first center hole 19 are provided with internal threads, and the upper joint can be connected to the downhole tubing through the internal threads at the upper end of the first through hole; the lower end of the upper joint 1 is provided with a first annular protrusion 13 and a second annular protrusion 14 in sequence around the first center hole 19, and the two annular protrusions are coaxially arranged with the first center hole 19, wherein the first annular protrusion 13 is located on the inner side of the second annular protrusion 14. The internal circulation hole 5 is provided on the first annular protrusion 13, and the internal circulation hole 5 can be provided with one, two or more. The upper end of the screen tube 2 is provided with an external thread, and the screen tube 2 is connected to the internal thread at the lower end of the first center hole 19 through the external thread provided at its upper end. The upper end of the central base pipe 3 is provided with an external thread, and the inner side of the first annular protrusion 13 is provided with an internal thread, and the central base pipe 3 is connected to the internal thread on the first annular protrusion 13 through the external thread provided at its upper end. The strong magnetic base tube 6 is provided with external threads at both ends. The inner side of the second annular protrusion 14 is provided with internal threads. The strong magnetic base tube 6 is connected to the inner threads of the second annular protrusion 14 via the external threads on its upper end. The outer tube 9 is provided with internal threads at its upper end. The outer side of the second annular protrusion 14 is provided with external threads. The outer tube 9 is connected to the outer threads of the second annular protrusion 14 via the internal threads on its upper end. The lower end of the second center hole 20 is provided with internal threads. The lower connector 12 can be connected to the downhole tubing string via the internal threads provided at the lower end of the second through hole. In other embodiments, the second center opening of the lower connector 12 can also be used as a bell mouth or suction port. The upper end of the lower connector 12 is provided with a third annular protrusion 15, which is provided with internal threads on its inner side. The strong magnetic base tube 6 is connected to the inner threads of the third annular protrusion 15 via the external threads on its lower end. This threaded connection allows for easy disassembly of the descaling device, thereby facilitating the cleaning of impurities within.

[0038] While the present invention has been described with reference to preferred embodiments, various modifications may be made and equivalent components may be substituted without departing from the scope of the present invention. In particular, the various technical features described in the various embodiments may be combined in any manner, provided no structural conflicts exist. The present invention is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A magnetic descaling device for underground operations, characterized in that: The invention comprises an upper joint, a screen tube, a central base pipe, an outer cylinder, and a lower joint; the upper joint has a first center hole, the lower joint has a second center hole, the upper joint and the lower joint are respectively connected to opposite ends of the outer cylinder, and the first center hole and the second center hole are connected through a cavity of the outer cylinder; the screen tube is disposed in the cavity of the outer cylinder, one end of the screen tube is open and the other end is closed, the open end of the screen tube is connected to the upper joint, and the opening of the screen tube is connected to the first center hole; a gap is left between the closed end of the screen tube and the lower joint; the central base pipe is disposed between the outer cylinder and the screen tube, and a first annular gap is formed between the inner wall of the central base pipe and the outer wall of the screen pipe; the end of the first annular gap near the upper joint is connected to the external space of the central base pipe through an internal circulation hole; the central base pipe is open at both ends, one end of the central base pipe is connected to the upper joint, and the other end of the central base pipe is connected to the lower joint with a gap; a plurality of groups of first magnets are mounted on the outer surface of the central base pipe, and the plurality of groups of first magnets are spaced apart along the axial direction of the central base pipe.

2. The magnetic descaling device for underground operations according to claim 1, characterized in that: A strong magnetic base tube is further provided between the outer tube and the central base tube. Both ends of the strong magnetic base tube are open, and the two ends of the strong magnetic base tube are respectively connected to the upper joint and the lower joint. A second annular gap is formed between the inner wall of the strong magnetic base tube and the outer wall of the central base tube. An end of the second annular gap close to the upper joint is connected to the first annular gap through the inner circulation hole, and an end of the second annular gap close to the lower joint is connected to the second center hole. A plurality of groups of second magnets are installed on the outer surface of the strong magnetic base tube, and the plurality of groups of second magnets are arranged at intervals along the axial direction of the strong magnetic base tube.

3. The magnetic descaling device for underground operation according to claim 2, characterized in that: A spiral groove is provided on the outer surface of the strong magnetic base tube, and the second magnet is installed in the spiral groove.

4. The magnetic descaling device for underground operation according to claim 2, characterized in that: A flexible steel wire is also provided on the strong magnetic base tube. One end of the flexible steel wire is fixed on the strong magnetic base tube, and the other end extends into the second annular gap.

5. The magnetic descaling device for underground operation according to claim 4, characterized in that: The flexible steel wires and the first magnets are distributed in a staggered manner.

6. The magnetic descaling device for underground operation according to claim 2, characterized in that: A third annular gap is formed between the outer wall of the strong magnetic base tube and the inner wall of the outer cylinder. External circulation holes are opened at both ends of the outer cylinder, and the external circulation holes are used to connect the third annular gap with the external space of the outer cylinder.

7. The magnetic descaling device for underground operation according to any one of claims 1 to 6, characterized in that: The outer cylinder is provided with a magnetic shield.

8. The magnetic descaling device for underground operation according to any one of claims 2 to 6, characterized in that: The upper end of the upper joint is used to connect the lower well pipe string, and the lower end of the upper joint is provided with a first annular protrusion and a second annular protrusion around the first center hole, the first annular protrusion is located on the inner side of the second annular protrusion, and the inner circulation hole is provided on the first annular protrusion; the screen pipe is connected to the internal thread of the first center hole by the external thread provided at its upper end; the central base pipe is connected to the internal thread on the first annular protrusion by the external thread provided at its upper end; the strong magnetic base pipe is connected to the internal thread on the second annular protrusion by the external thread provided at its upper end; the outer cylinder is connected to the external thread on the second annular protrusion by the internal thread provided at its upper end; the upper end of the lower joint is provided with a third annular protrusion, and the strong magnetic base pipe is connected to the internal thread on the third annular protrusion by the external thread provided at its lower end.

9. The magnetic descaling device for underground operation according to any one of claims 2 to 6, characterized in that: The central base tube and the strong magnetic base tube are made of steel.

10. The magnetic descaling device for underground operation according to any one of claims 1 to 6, characterized in that: The outer wall of the screen tube is wrapped with several layers of filter screens to form a filter screen tube.

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