Underground sucker rod displacement testing device

Abstract

The utility model discloses a displacement testing device for an underground sucker rod. The displacement testing device comprises a detection pipe joint and a detection lantern ring, the detection pipe section comprises a pipe body, a magnetostrictive waveguide wire and an induction coil are arranged in the pipe body, one end of the magnetostrictive waveguide wire is arranged in the induction coil, an electronic bin is arranged on the outer wall of the pipe body, the waveguide wire and the induction coil are connected with the electronic bin through lead-out wires, and the electronic bin is provided with a power supply and signal wire; the detection lantern ring comprises a vernier magnetic ring, and the detection lantern ring is arranged on a sucker rod in a sleeving mode when the detection lantern ring is used. Displacement data of the underground sucker rod can be tested in real time, displacement signals output by the magnetostriction displacement sensor are absolute values, the underground sucker rod displacement measuring device has the advantages of being high in precision, high in response, low in hysteresis, non-contact, long in service life, high in stability and the like, regular calibration and maintenance are not needed, and the underground sucker rod displacement measuring device is suitable for large-scale popularization and application. And the requirement of underground sucker rod displacement measurement can be met.

Description

Technical Field

[0001] This utility model relates to the field of oil production equipment technology, specifically a downhole sucker rod displacement testing device. Background Technology

[0002] The oil production system of a pumping unit well mainly consists of a surface pumping unit, wellhead, sucker rod, tubing, and downhole pump. The surface pumping unit drives the sucker rod to move up and down reciprocally, which in turn drives the downhole pump to pressurize and bring the produced fluid from the well to the surface. The sucker rod connects the surface pumping unit and the downhole pump. Metal sucker rods are made of high-strength metal alloy materials with an elastic modulus of 210 GPa. Non-metallic sucker rods are mainly made of glass fiber and resin composite materials, and carbon fiber and resin composite materials. Alternatively, carbon fiber and glass fiber can be combined with resin to form a sucker rod.

[0003] The elastic modulus of fiberglass sucker rods is approximately 80 GPa, while that of carbon fiber sucker rods is approximately 130 GPa. Regardless of whether the sucker rod is metal or non-metal, during the pumping process, the load on the sucker rod changes as the liquid column load is applied and unloaded on the pump plunger. The sucker rod elongates or shortens with these changes in force, resulting in a difference between the up-and-down stroke of the sucker rod and the stroke of the suspension point on the surface. This difference is known as stroke loss. Fiberglass and carbon fiber sucker rods, with their lower elastic modulus, elongate or shorten more significantly with these changes in force, leading to greater stroke loss and a greater impact on pump efficiency. This should be given sufficient attention. While existing technology can relatively easily obtain the suspension point load and displacement when measuring the dynamometer card of the pumping unit well, the testing of downhole sucker rod displacement is difficult due to the lack of mature testing technology, making the testing of downhole sucker rod dynamometer cards a technical challenge in the industry.

[0004] Announcement No. CN214741284U discloses a detection device for the load and displacement of the polished rod of an oil pumping unit, including a housing, a pressure sensor, a power supply box, a left partition, a displacement sensor, a circuit board, a right partition, a high-frequency cable, and an antenna. The pressure sensor is disposed inside the housing and has a cylindrical structure, with its upper and lower ends in close contact with the inner walls of the upper and lower end covers of the housing. The power supply box is fitted and installed with the left partition. The displacement sensor is soldered inside the circuit board, which is fitted and installed with the right partition. The antenna is connected to the circuit board through the high-frequency cable.

[0005] This existing technology is set up above the well, located on the surface, and does not involve downhole sucker rod displacement testing.

[0006] Publication No. CN112682028A discloses a device and method for real-time testing and wireless transmission of pump dynamometer diagrams for rod pumps in oil wells. The device includes a battery pack, a magnetostrictive acoustic converter, a system power supply, a displacement sensor, a circuit board, a load sensor, a housing, and a ground controller. The battery pack, magnetostrictive acoustic converter, system power supply, displacement sensor, circuit board, and load sensor are all housed inside the housing. The ground controller is positioned on the surface of the oil well near the wellhead. The battery pack is electrically connected to the system power supply, which is also electrically connected to the displacement sensor and the load sensor. The displacement sensor and load sensor are also connected to the circuit board, which is electrically connected to the magnetostrictive acoustic converter. The magnetostrictive acoustic converter is wirelessly connected to the ground controller.

[0007] The existing technology is installed underground and does not involve specific methods for testing displacement. The magnetostrictive acoustic energy converter involved converts displacement and load parameters into acoustic vibration signals with data information. It is not the same device as the magnetostrictive waveguide wire involved in this patent. The signal transmission involved is wireless, while this patent uses a wired method.

[0008] Publication No. CN117127963A discloses a load testing device and method for a dynamometer diagram of a flexible polished rod in a pumping unit well. The device includes a drum, a flexible polished rod, a centralizing wheel, a support rod, a tower, and a bearing housing. It also includes a first sensor and a pressure sensor. The pressure sensor is mounted on the bearing housing, and the first sensor is mounted on the drum. The device places the pressure sensor on the bearing housing between the centralizing wheel and the tower. The pressure sensor is at an angle to the support rod, making the direction of the pressure sensor perpendicular to the direction of the supporting force exerted by the centralizing wheel on the flexible polished rod. An angle sensor is used to test the displacement of the flexible polished rod, thereby accurately obtaining the dynamometer diagram of the flexible polished rod.

[0009] This existing technology is set up above the well, located on the surface, and does not involve downhole sucker rod displacement testing.

[0010] In summary, the technical solutions, technical problems to be solved, and beneficial effects of the above-disclosed technologies are all different from those of this utility model. For more technical features, technical problems to be solved, and beneficial effects of this utility model, the above-disclosed technical documents do not provide any technical inspiration. Utility Model Content

[0011] In view of the above-mentioned defects in the existing technology, the purpose of this utility model is to provide a downhole sucker rod displacement testing device.

[0012] To achieve the above objectives, the present invention adopts the following technical solution:

[0013] A downhole sucker rod displacement testing device includes a testing section and a testing collar. The testing section includes a pipe body, in which a magnetostrictive waveguide wire and an induction coil are disposed. One end of the magnetostrictive waveguide wire is inside the induction coil. An electronic chamber is disposed on the outer wall of the pipe body. The waveguide wire and the induction coil are both connected to the electronic chamber via lead wires. The electronic chamber is provided with power supply and signal lines. The testing collar includes a vernier magnetic ring, which is fitted onto the sucker rod during use.

[0014] Furthermore, the pipe body includes an oil pipe and an inner liner pipe;

[0015] Specifically, the waveguide wire and induction coil are arranged inside the inner liner tube, the outer wall of the oil pipe is provided with an electronic compartment, the oil pipe wall is provided with an outlet, the lead wire passes through the inner liner tube, passes through the outlet and connects to the electronic compartment, and the outer wall of the oil pipe is provided with an oil pipe sealing clamp to seal the radial through hole.

[0016] Furthermore, the detection collar includes a centralizer, and a vernier magnetic ring is disposed inside the centralizer.

[0017] Furthermore, the end of the waveguide wire away from the lead wire is connected to an energy-absorbing material that absorbs the stretching strain wave.

[0018] Furthermore, a hanging basket is provided on the outer wall of the oil pipe, and an electronic compartment is provided inside the hanging basket.

[0019] Furthermore, the inner liner tube is made of plastic, and a groove is provided on the outer wall of the inner liner tube. The waveguide wire and the induction coil are placed in the groove, and the groove containing the waveguide wire and the induction coil is filled with hot melt adhesive.

[0020] Furthermore, the electronic compartment is connected to the lead wires, power supply and signal lines through a cable sealing connector. The electronic compartment is equipped with a pulse emission circuit and an amplification circuit. The pulse emission circuit is connected to the waveguide wire, and the amplification circuit is connected to the induction coil.

[0021] Specifically, the lead wires are multi-core insulated wires that connect the waveguide wire and the induction coil respectively. The wires connecting the waveguide wire are used to transmit current pulses from the electronic compartment to the waveguide wire, and the wires connecting the induction coil are used to transmit the magnetic induction electromotive force of the induction coil to the electronic compartment.

[0022] Furthermore, the outlet is elliptical, with the major axis of the ellipse parallel to the longitudinal direction of the oil pipe and the minor axis of the ellipse larger than the outer diameter of the lead wire. The outlet is filled with resin to fix the lead wire.

[0023] Furthermore, the oil pipe sealing clamp consists of two saddle-shaped clamps that are locked onto the outlet of the oil pipe. The oil pipe sealing clamp contains sealing material and a wiring groove. The lead wire passes through the wiring groove, and the sealing material seals the outlet.

[0024] Furthermore, the vernier magnetic ring is a neodymium iron boron permanent magnet, composed of two semi-circular annular magnets connected together by opposite magnetic poles, and the inner diameter of the vernier magnetic ring is larger than the outer diameter of the sucker rod.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] This invention can measure the displacement data of downhole sucker rod in real time. The magnetostrictive displacement sensor on which this invention is based outputs an absolute displacement signal, which has the advantages of high precision, high response, low hysteresis, non-contact operation, long life and high stability. It does not require periodic calibration and maintenance and can meet the needs of downhole sucker rod displacement measurement. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of a downhole sucker rod displacement testing device according to this utility model.

[0028] In the diagram: 1-Suck rod; 2-Tubing; 3-Inner liner; 4-Waveguide wire; 5-Leading wire; 6-Induction coil; 7-Energy absorbing material; 8-Power supply and signal line; 9-Electronic compartment; 10-Tubing sealing clamp; 11-Basket; 12-Center; 13-Vernier magnetic ring. Detailed Implementation

[0029] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0030] Example 1:

[0031] Please see Figure 1 The present invention provides a downhole sucker rod displacement testing device, including a detection tube section and a detection collar. The detection collar is sleeved on the sucker rod 1. When the detection collar passes through the detection tube section, the position of the detection collar is obtained, and then the displacement of the sucker rod 1 is detected.

[0032] Furthermore, the detection tube section includes a tube body, in which a magnetostrictive waveguide wire 4 and an induction coil 6 are disposed. One end of the magnetostrictive waveguide wire 4 is inside the induction coil 6. An electronic compartment 9 is disposed on the outer wall of the tube body. The waveguide wire 4 and the induction coil 6 are both electrically connected to the electronic compartment 9 through lead wires 5. The electronic compartment 9 is provided with power supply and signal lines 8 for electrical connection with the top control device.

[0033] Furthermore, the detection collar includes a centralizer 12, and a vernier magnetic ring 13 is disposed inside the centralizer 12.

[0034] Specifically, the pipe body includes an oil pipe 2 and an inner liner pipe 3. The waveguide wire 4 and the induction coil 6 are disposed inside the inner liner pipe 3. A hanging basket 11 is welded to the outer wall of the oil pipe 2. An electronic compartment 9 is disposed inside the hanging basket 11. An outlet is provided on the wall of the oil pipe 2. The lead wire 5 passes through the inner liner pipe 3, through the outlet, through the hanging basket 11, and then connects to the electronic compartment 9. An oil pipe sealing clamp 10 is provided on the outer wall of the oil pipe 2 to seal the radial through hole.

[0035] Specifically, the end of the waveguide wire 4 away from the lead wire 5 is connected to an energy-absorbing material that absorbs the stretching strain wave.

[0036] Specifically, a vernier magnetic ring 13 is installed at the flange position of the sucker rod 1. The vernier magnetic ring 13 is fixed by setting a clamp on the sucker rod 1 above the vernier magnetic ring 13. The detection pipe section with the magnetostrictive waveguide wire 4 installed and the sucker rod 1 with the vernier magnetic ring 13 installed are in the same well section in the well.

[0037] Example 2:

[0038] Based on Example 1, this example provides a more specific downhole sucker rod displacement testing device.

[0039] The inner liner tube 3 is made of plastic, the same material as the plastic liner tubes used in the petroleum industry. Ultra-high molecular weight polyethylene can be used, and the wall thickness can be increased to a certain extent, for example, to 5-8 mm. A groove is machined on the outer wall of the tube using a mechanical processing method. The groove width is 1 mm for the part where the waveguide wire 4 is placed, 3 mm for the part where the induction coil 6 is placed, and 3 mm for the part where the lead wire 5 is placed. The length of the groove is based on the width corresponding to the placed waveguide wire 4, induction coil 6, and lead wire 5. The depth of the groove is based on the fact that the waveguide wire 4, induction coil 6, and lead wire 5 are all embedded 1 mm below the surface of the plastic inner liner tube 3.

[0040] The waveguide wire 4 is 1m shorter than the length of the plastic inner tube 3, for example, less than 8m in length and less than 0.8mm in diameter. Fe-Ga waveguide wire can be selected. The end of the waveguide wire 4 away from the lead wire 5 has an energy-absorbing material 7, such as rubber, that absorbs the strain wave. The starting end is connected to the magnetic induction coil 6 and leads out the wire 5. The waveguide wire 4, the magnetic induction coil and the lead wire 5 are placed in the groove of the plastic inner tube 3. The groove of the plastic inner tube 3 at the part of the waveguide wire 4 and the induction coil 6 is filled with plastic hot melt glue. The groove at the part corresponding to the lead wire 5 is not filled, so that it is in an open state.

[0041] The lead wire 5 is a multi-core insulated wire, with multiple wires connecting the waveguide wire 4 and the induction coil 6 respectively. The wire connected to the waveguide wire 4 is used to transmit current pulses from the electronic compartment 9 to the waveguide wire 4, and the wire connected to the induction coil 6 is used to transmit the magnetic induction electromotive force of the induction coil 6 to the electronic compartment 9.

[0042] The outlet is formed by machining a hole near the end of the oil pipe 2. The hole is elliptical in shape, with the major axis of the ellipse parallel to the longitudinal direction of the oil pipe 2 and the minor axis of the ellipse slightly larger than the outer diameter of the lead wire 5.

[0043] During the process of inserting the plastic inner tube 3 into the oil pipe 2, when the lead wire 5 is just at the outlet, tweezers are inserted from the outlet to hold the head of the lead wire 5 and pull it out of the outlet. The plastic inner tube 3 is then pushed into the oil pipe 2 while the lead wire 5 is pulled out until the front part of the plastic inner tube 3 is exposed from the oil pipe 2. The two ends of the oil pipe 2 are then flanged according to the process of making the plastic inner tube 3 to make a plastic inner oil pipe. The outlet is filled with high-strength resin to fix the lead wire 5 and the outlet in the high-strength resin.

[0044] The oil pipe sealing clamp 10 consists of two saddle-shaped clamps that are locked onto the outlet. The oil pipe sealing clamp 10 contains sealing material and a cable tray. The lead wire 5 is passed through the cable tray, and the tightening bolt is tightened. In this way, the sealing material forms a seal on the outlet, and the sealing material in the cable tray forms a seal on the lead wire 5. The lead wire 5 is led out along the cable tray and then to the electronic compartment 9 in the hanging basket 11. The sealing material consists of a sealing ring and a sealing plug. The sealing ring seals the oil pipe sealing clamp 10 and the oil pipe 2 above and below the outlet. The sealing plug seals the lead wire 5 and the cable tray. The sealing plug and the sealing ring partially overlap to achieve a complete seal between the oil pipe sealing clamp 10 and the oil pipe 2.

[0045] The electronic compartment 9 is connected to the lead wire 5 and the power supply and signal line 8 via a cable sealing connector. The electronic compartment 9 contains a pulse transmitting circuit and an amplification circuit. The electronic compartment 9 has the function of sending current pulses to the waveguide wire 4 and receiving and amplifying the induced electromotive force (EMF). The amplified EMF is transmitted to the main control system along the power supply and signal line 8. It should be noted that the pulse transmitting circuit and the amplification circuit are existing technologies, and those skilled in the art are aware of them.

[0046] The power supply and signal lines 8 are multi-core insulated wires. The power supply wire transmits power from the ground main control system to the electronic compartment 9, while the signal wire transmits control commands from the main control system to the electronic compartment 9 and transmits the amplified induced electromotive force from the electronic compartment 9 back to the main control system. The power supply and signal lines 8 are arranged along the outside of the oil pipes 2. Cable clamps are used to fix the power supply and signal lines 8 to each oil pipe 2, with two cable clamps on each pipe 2. At the couplings of the oil pipes 2, protective devices are used to cover the power supply and signal lines 8 to prevent them from being collided, squeezed, or worn by the couplings and inner walls of the casing.

[0047] The main control system is located on the surface of the oil well and is connected to the power supply and signal line 8. The main control system is responsible for the power supply of the entire system, standard clock, pulse current generation, magnetic induction electromotive force reception, calculation of the displacement of the vernier magnetic ring 13 corresponding to each pulse current, and storage of test data.

[0048] The vernier magnetic ring 13 is a neodymium iron boron permanent magnet, shaped like a ring, composed of two semi-circular annular magnets connected together with opposite magnetic poles. Its inner diameter is slightly larger than the outer diameter of the sucker rod 1. The vernier magnetic ring 13 is fitted onto the sucker rod 1. A nylon centralizer 12 is manufactured by injection molding, and the vernier magnetic ring 13 is fixed to the sucker rod 1 along with the nylon centralizer 12. The outer diameter of the nylon centralizer 12 is slightly larger than the outer diameter of the magnetic ring.

[0049] Example 3:

[0050] Based on Example 2, this example provides a method for using a downhole sucker rod displacement testing device, including the following steps:

[0051] During oil well operations, during the running of tubing 2, when running the inspection tubing section with basket 11 to the planned depth, connect the lead wire 5 to the electronic compartment 9, and connect the power supply and signal line 8 to the electronic compartment 9. Then, run tubing 2 sequentially, and secure the power supply and signal line 8 one by one with cable clamps. When running sucker rod 1, run sucker rod 1 with vernier magnetic ring 13 to the planned depth. At the bottom dead center of the pumping unit, position the vernier magnetic ring 13 at the corresponding position of the waveguide wire 4. During one stroke, the range of the vernier magnetic ring 13 moving up and down with the sucker rod 1 is entirely within the well section where the waveguide wire 4 is located.

[0052] During the upstroke of the pumping unit, the vernier magnetic ring 13 moves upward with the sucker rod 1. The surface control system sends a pulse current command to the electronic compartment 9. The electronic compartment 9 emits a pulse current, which is transmitted along the lead wire 5 to the waveguide wire 4. The pulse current propagates along the waveguide wire 4, and the circular magnetic field established along the stroke propagates along the waveguide wire 4. When it encounters the magnetic field of the vernier magnetic ring 13, due to the magnetostrictive effect, a mechanical strain pulse is generated at the intersection of the magnetic fields on the waveguide wire 4, and it propagates in two directions along the waveguide wire 4 at the speed of sound. The strain pulse transmitted at the end is absorbed by the energy-absorbing material 7 at the end. When the strain pulse transmitted towards the induction coil 6 encounters the induction coil 6, an induced electromotive force is generated on the coil. This electromotive force is transmitted to the electronic compartment 9 along the lead wire 5. After being detected and amplified by the circuit of the electronic compartment 9, it is transmitted to the ground main control system. By measuring the time between the initial pulse and the induced electromotive force and multiplying it by the fixed sound speed of the pulse propagation, the actual distance of the vernier magnetic ring 13 can be calculated, and thus the position of the sucker rod 1 and the displacement of the sucker rod 1 can be obtained.

[0053] When the pumping unit is working, the displacement testing principle is the same as during the downstroke.

[0054] During one stroke, the number of times the ground control system sends pulse current commands to the electronic compartment 9 is determined based on the number of displacements that need to be tested in one stroke of the pumping unit well. Generally, sending 200 pulses is sufficient to meet the requirements, and the pulses are at equal time intervals.

[0055] All components not discussed in detail in this application, as well as the connection methods of these components, are well-known technologies in this field. They can be directly applied and will not be elaborated further.

[0056] In this utility model, the term "multiple" refers to two or more unless otherwise explicitly defined. The terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; "linking" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0057] In the description of this utility model, it should be understood that the terms "upper", "lower", "left", "right", "front", "rear", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or unit referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0058] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which 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.

[0059] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A downhole sucker rod displacement testing device, characterized by, Including testing pipe sections and testing collars; The detection tube section includes a tube body, in which a magnetostrictive waveguide wire and an induction coil are disposed. One end of the magnetostrictive waveguide wire is inside the induction coil. An electronic compartment is disposed on the outer wall of the tube body. The waveguide wire and the induction coil are both connected to the electronic compartment through lead wires. The electronic compartment is provided with power supply and signal lines. The detection collar includes a vernier magnetic ring, which is fitted onto the sucker rod during use.

2. A downhole sucker rod displacement test device according to claim 1, characterized in that, The pipe body includes an oil pipe and an inner liner pipe; The waveguide wire and induction coil are arranged inside the inner liner tube. An electronic compartment is arranged on the outer wall of the oil pipe. An outlet is arranged on the oil pipe wall. The lead wire passes through the inner liner tube, passes through the outlet, and connects to the electronic compartment. An oil pipe sealing clamp is arranged on the outer wall of the oil pipe to seal the radial through hole.

3. A downhole sucker rod displacement test device according to claim 1, characterized in that, The detection collar includes a centralizer, and a vernier magnetic ring is disposed inside the centralizer.

4. The downhole sucker rod displacement test device of claim 1, wherein, The end of the waveguide wire furthest from the lead wire is connected to an energy-absorbing material that absorbs expansion and contraction strain waves.

5. A downhole sucker rod displacement test device according to claim 2, characterized in that, A hanging basket is installed on the outer wall of the oil pipe, and an electronic compartment is installed inside the hanging basket.

6. A downhole sucker rod displacement test device according to claim 2, characterized in that, The inner liner tube is made of plastic, and a groove is provided on the outer wall of the inner liner tube. The waveguide wire and the induction coil are placed in the groove, and the groove containing the waveguide wire and the induction coil is filled with hot melt adhesive.

7. The downhole sucker rod displacement test device of claim 1, wherein, The electronic compartment is connected to the lead wires, power supply and signal lines through a cable sealing connector. The electronic compartment is equipped with a pulse emission circuit and an amplification circuit. The pulse emission circuit is connected to the waveguide wire, and the amplification circuit is connected to the induction coil. The lead-out wires are multi-core insulated wires that connect the waveguide wire and the induction coil respectively. The wires connecting the waveguide wire are used to transmit current pulses from the electronic compartment to the waveguide wire, and the wires connecting the induction coil are used to transmit the magnetic induction electromotive force of the induction coil to the electronic compartment.

8. A downhole sucker rod displacement test device according to claim 2, characterized in that, The outlet is elliptical, with the major axis of the ellipse parallel to the longitudinal direction of the oil pipe and the minor axis of the ellipse larger than the outer diameter of the lead wire. The outlet is filled with resin to fix the lead wire.

9. The downhole sucker rod displacement test device of claim 2, wherein, The oil pipe sealing clamp consists of two saddle-shaped clamps that are locked onto the outlet of the oil pipe. The oil pipe sealing clamp contains sealing material and a wiring groove. The lead wire passes through the wiring groove, and the sealing material seals the outlet.

10. The downhole sucker rod displacement test apparatus of claim 1, wherein, The vernier magnetic ring is a neodymium iron boron permanent magnet, consisting of two semi-circular annular magnets connected together by opposite magnetic poles. The inner diameter of the vernier magnetic ring is larger than the outer diameter of the sucker rod.

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