Submersible linear motor well fluid isolation mechanism

Abstract

The present application relates to oil exploitation downhole equipment technical field, more specifically, it is a kind of submersible linear motor well fluid isolation mechanism, comprising: upper light shaft, its upper end is out of the sealing cavity shell, lower end is connected with the upper end of the mover;Lower light shaft, its upper end is connected with the lower end of the mover, lower end is out of the sealing cavity shell;Electromagnetic structure, including mover and stator winding, electromagnetic structure is covered in the sealing cavity shell inside, the reciprocating motion of mover drives the synchronous movement of the upper light shaft and the lower light shaft;Upper seal, set in the upper part of the sealing cavity shell, for sealing the upper light shaft;Piston seal, set in the lower part of the sealing cavity shell, for sealing the lower light shaft;Pressure compensation element, set in the lower side of the piston seal, for applying pre-pressure to the piston seal, so that the pressure in the cavity of the electromagnetic structure is higher than the external environment pressure, maintain motor inner chamber micro-positive pressure, realize dynamic sealing and pressure balance.

Description

Technical Field

[0001] This invention relates to the field of downhole equipment technology for oil extraction, and more specifically to a submersible linear motor well fluid isolation mechanism. Background Technology

[0002] Reciprocating submersible linear motors are the core drive unit in downhole rodless oil recovery technology. They employ a moving-magnet cylindrical permanent magnet linear motor design. This design requires a strict seal between the mover and stator to ensure a clean air gap, providing optimal motor operating conditions and effectively extending the motor's lifespan. Existing reciprocating submersible linear motors have the following core defects:

[0003] Open structure: The electromagnetic structure of the motor is exposed to media containing oil, water, sand, wax, mechanical impurities, gas, and corrosive substances. Well fluid intrudes into the electromagnetic structure of the reciprocating submersible linear motor, leading to problems such as corrosion, insulation aging, permanent magnet demagnetization, air gap blockage, and jamming.

[0004] Closed-loop structure: The motor is immersed in high-temperature, high-pressure well fluid in a deep well. The external pressure of the downhole motor is much higher than the internal force, causing the mover to seize and the motor to stop. The seals wear, deform under pressure, and the medium leaks, leading to seal failure.

[0005] Balancing structures such as bellows and airbags: Thin-walled metal corrugated hoses, elastic material airbags, and piston rods are used to balance the pressure difference inside and outside the motor. Long-term reciprocating motion of the bellows can easily lead to metal fatigue and cracking, resulting in seal failure.

[0006] Piston-buffered breathing structure: It adopts the reciprocating motion of a single piston to change the internal volume of the motor and balance the pressure difference between the inside and outside of the motor in each stroke. However, the balance response is slow and the dynamic adaptability is poor.

[0007] In summary, the electromagnetic structure of existing dual submersible linear motors is easily damaged, and there is still room for improvement in terms of seal failure, slow balance response, and dynamic adaptability. Summary of the Invention

[0008] This invention provides a submersible linear motor well fluid isolation mechanism, which aims to prevent contaminants from entering the motor sealing cavity, while maintaining a slight positive pressure inside the motor cavity to achieve dynamic sealing and pressure balance, reduce sealing friction and wear, and extend motor life.

[0009] The above objectives are achieved through the following technical solutions:

[0010] A submersible linear motor well fluid isolation mechanism includes:

[0011] Sealed cavity shell;

[0012] The upper optical axis extends out of the sealed cavity shell at its upper end and is connected to the upper end of the mover at its lower end.

[0013] The lower optical axis has its upper end connected to the lower end of the mover, and its lower end extends out of the sealed cavity shell.

[0014] The electromagnetic structure includes a mover and a stator winding. The electromagnetic structure is enclosed inside the sealed cavity shell. When the mover reciprocates, it drives the upper optical axis and the lower optical axis to move synchronously.

[0015] An upper seal is provided at the upper part of the outer shell of the sealing cavity to seal the upper optical axis;

[0016] A piston seal is disposed at the lower part of the outer shell of the sealing cavity and is used to seal the lower optical axis;

[0017] A pressure compensation element is disposed on the lower side of the piston seal to apply pre-pressure to the piston seal, so that the pressure inside the cavity where the electromagnetic structure is located is higher than the external ambient pressure.

[0018] The upper seal, along the axis of the upper optical shaft, is sequentially arranged from the well fluid side to the motor oil side with a first dustproof ring, a first step seal, a first Y-type sealing ring, a first support ring, a second Y-type sealing ring, a second step seal, and a second support ring. The first dustproof ring is located at the top and is used to prevent coarse sand particles and impurities from entering the sealing assembly. The first step seal is a combined seal, including an O-ring and a PTFE slip ring. The lip of the first Y-type sealing ring faces upwards and mates with the first support ring. The lip of the second Y-type sealing ring faces downwards. The second support ring is used for axial positioning and support.

[0019] An outer sealing element is embedded on the outer circumferential surface of the piston seal, the outer sealing element including a third support ring, a fifth support ring and a V-group seal; an inner sealing element is embedded on the inner circumferential surface of the piston seal, the inner sealing element including a fourth support ring, a third step seal, a third Y-type sealing ring, a fourth Y-type sealing ring, a fourth step seal and a second dustproof ring.

[0020] The pressure compensation element is a pre-compression spring. The pre-compression spring applies a pre-pressure that makes the pressure inside the cavity where the electromagnetic structure is located 0.1 MPa greater than the external ambient pressure, thus creating a slightly positive pressure environment.

[0021] The pressure compensation element includes an electrically controlled pushrod array, which is disposed on the lower side of the piston seal and is used to apply an adjustable axial preload to the piston seal. A multi-parameter sensor array and a downhole controller are disposed on the outer shell of the sealing cavity. The multi-parameter sensor array includes a differential pressure sensor, a temperature sensor, a stroke encoder, and a current sensor. The signal output terminals of each sensor are connected to the signal input terminal of the downhole controller via armored cables. The control signal output terminal of the downhole controller is connected to the drive input terminal of the electrically controlled pushrod array, forming a closed-loop adaptive control system. The downhole controller calculates a comprehensive sealing health index based on the data collected by the multi-parameter sensor array and outputs a control signal to the electrically controlled pushrod array according to the threshold conditions of the comprehensive sealing health index to adjust the magnitude of the axial preload.

[0022] The power supply system includes a power supply unit in the ground control cabinet. The power supply unit uses armored cables to supply the push rod servo driver, the downhole controller, and the multi-parameter sensor array respectively. The communication system uses a power line carrier channel with multiplexed armored cable power cores to transmit downlink control commands and uplink status data. When communication is interrupted, the downhole controller switches to autonomous operation mode and continues to perform sealing health comprehensive index grading and push rod control according to the locally stored default thresholds.

[0023] The upper optical axis and the mover are connected by universal joints, and the lower optical axis and the mover are connected by universal joints. The universal joints are ball-head type and have multi-degree-of-freedom rotation capability, which are used to compensate for the coaxiality deviation between adjacent optical axes.

[0024] The outer shell of the sealing cavity is fitted with a sand-proof sleeve, which is located below the piston seal and is used to prevent coarse sand particles in the well fluid from entering the sealing area.

[0025] The oil groove notch bushing is disposed between the outer shell of the sealing cavity and the stator winding, and is used to straighten the mover to reduce uneven wear.

[0026] The sealed cavity shell is divided into an upper section and a lower section, which are connected by a segmented flange. The length of a single section does not exceed 10 meters. The electromagnetic structure is correspondingly divided into an upper motor section and a lower motor section. Adjacent moving parts are connected by universal joints. The cross-sectional areas of the upper optical shaft and the lower optical shaft are the same.

[0027] The beneficial effects of the submersible linear motor well fluid isolation mechanism of the present invention are as follows:

[0028] Pressure balance: The electromagnetic structure of the motor is placed in the sealed cavity. The two ends of the electromagnetic structure mover are respectively connected to an optical shaft with the same cross-sectional area. The optical shaft passes through the scraping structure and sealing ring of the sealed cavity. When it reciprocates, the throughput at both ends is consistent to achieve pressure balance.

[0029] Breathing structure: One end of the motor sealing chamber is a smooth rod seal, and the other end is a piston seal added on the basis of the smooth rod seal. The motor sealing chamber is filled with motor oil. Through the adaptive movement of the piston, the pressure difference between the inside and outside of the motor chamber is balanced, effectively isolating the well fluid from the motor cavity and ensuring that the motor works in a clean environment.

[0030] Micro-positive pressure: A pressure compensation element with pre-pressure is installed at the bottom of the piston. The pressure in the motor sealing chamber is 0.1 MPa higher than the ambient pressure. This reduces friction on the sealing ring and minimizes wear. Throughout the motor's lifespan, motor oil only flows out of the sealing chamber, preventing well fluid from entering the motor cavity.

[0031] Segmented structure: The motor is divided into 2 sections, each no more than 10 meters long. The mover is connected by a universal joint, and the main frame is connected by a flange. After connection, oil is injected and vented through a one-way valve and sealing plug integrated mechanism. After being injected to a slightly positive pressure, it is sealed, which can adapt to the working conditions of the oilfield. Attached Figure Description

[0032] Figure 1 A schematic diagram of the upper part of a submersible linear motor well fluid isolation mechanism is shown.

[0033] Figure 2 A schematic diagram of the lower half of a submersible linear motor well fluid isolation mechanism is shown.

[0034] Figure 3 A schematic diagram of the upper seal structure is shown;

[0035] Figure 4 A schematic diagram of the piston seal structure is shown;

[0036] Figure 5 A schematic diagram of the motor segments is shown;

[0037] Figure 6 The curves showing the wear rate per kilometer of the sealing material under different pressure differentials are displayed. Figure 1 ;

[0038] Figure 7 The curves showing the wear rate per kilometer of the sealing material under different pressure differentials are displayed. Figure 2 .

[0039] Attached Figure Descriptions: 1. Upper Seal; 2. Upper Optical Shaft; 3. Ambient Temperature and Pressure Sensor; 4. Armored Cable; 5. Universal Joint; 6. Mover; 7. Stator Winding; 8. Oil Sump Notch Bushing; 9. Oil Drain Port; 10. Oil Inlet Port; 11. Segmented Flange; 12. Piston Seal; 13. Preload Spring; 14. Sandproof Sleeve; 15. Limiting Block; 16. Buffer Block; 1a. First Dustproof Ring; 2a. First Step Seal; 3a. First Y-Type Seal 4a. First support ring; 5a. Second Y-type seal ring; 6a. Second step seal; 7a. Second support ring; 8a. Air outlet; 9a. Third support ring; 10a. Fourth support ring; 11a. Third step seal; 12a. Piston seal; 13a. Fifth support ring; 14a. Third Y-type seal ring; 15a. V-group seal; 16a. Fourth Y-type seal ring; 17a. Fourth step seal; 18a. Second dustproof ring. 1b. Upper section of motor; 2b. Lower section of motor; 3b. O-ring; 4b. Segmented lower flange adapter clamp; 5b. Universal joint sleeve; 6b. Lower optical shaft; 7b. Mover spindle; 8b. End-sealing upper flange adapter clamp; 9b. Universal joint ball seat. Detailed Implementation

[0040] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0041] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0042] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0043] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0044] A submersible linear motor well fluid isolation mechanism includes a sealed cavity shell. The upper part of the sealed cavity shell is an upper seal 1, through which an upper optical shaft 2 extends. The sealing assembly of the upper seal 1, along the axial direction of the upper optical shaft 2, has the following components arranged sequentially from the well fluid side to the motor oil side. Each component is press-fitted into a groove in the inner wall of the upper seal 1, achieving an embedded installation, and axially abutting against each other:

[0045] The first dustproof ring 1a is located on the uppermost side, i.e. the well fluid side, and is radially embedded in the uppermost hole groove of the inner wall of the upper seal 1. It is used to prevent coarse sand particles, dirt and impurities from entering the sealing assembly and to protect the subsequent precision seals. The lip of the first dustproof ring 1a faces upward and is in contact with the outer diameter surface of the upper optical shaft 2.

[0046] The first step seal 2a, located immediately below the first dustproof ring 1a, is a combined seal, including a rectangular cross-section O-ring and a PTFE slip ring. The O-ring is an elastic pre-compression element that provides radial elastic force to keep the PTFE slip ring tightly against the upper optical axis 2, achieving a reciprocating seal with low friction and low wear.

[0047] The first Y-shaped sealing ring 3a is located immediately below the step seal 2a, with its lip facing upwards (the high-pressure side). Utilizing a self-sealing principle, it enhances the sealing effect as external pressure increases. The first Y-shaped sealing ring 3a mates with the first support ring 4a, which is installed on the open side (the lower side) of the first Y-shaped sealing ring 3a to prevent it from flipping or being squeezed out under high pressure. The first support ring 4a forms an axial limiting relationship with its matching groove. The first step seal 2a and the first Y-shaped sealing ring 3a are axially clamped and positioned by the first dustproof ring 1a and the adjacent first support ring 4a.

[0048] The second Y-shaped sealing ring 5a is arranged downwards, with the lip of the second Y-shaped sealing ring 5a facing downwards to prevent motor oil leakage; the second step seal 6a is adjacent to the lower side of the second Y-shaped sealing ring 5a to further enhance the sealing redundancy; the lower side of the second step seal 6a is provided with a second support ring 7a for axial positioning and support to prevent the seal from moving axially under alternating pressure.

[0049] An outlet 8a is provided on the upper seal 1, located below the second support ring 7a, for discharging residual gas in the chamber during the installation and commissioning of the upper seal 1a. After use, it is sealed by a screw plug and is in a sealed state during normal operation.

[0050] The outer shell of the sealing cavity consists of, from top to bottom, a coupling with a sealing ring groove, namely the upper seal 1, the first 2-3 / 8 oil pipe, the main shell of the protective coil, the second 2-3 / 8 oil pipe, and the piston seal 12. Oil pipes of different sizes are connected using adapter couplings. The threads of the adapter couplings are TBG oil pipe threads that conform to the API push rod 5B standard, ensuring reliable sealing.

[0051] The upper section of the upper optical shaft 2 is connected to the plunger pump rod via a ball joint. The upper optical shaft 2 is made of 42CrMo material, tempered to HB230-260, and after being machined to the appropriate size, it is plated with hard chrome to resist wear and prevent the accumulation of sand and gravel. It is ground to a surface roughness of Ra0.32. At this time, a molecular oil film is formed between the upper optical shaft 2 and the seal, resulting in minimal friction and optimal sealing effect.

[0052] The upper seal 1 is internally threaded with a section of sandproof sleeve. The other end of the sandproof sleeve is connected to the plunger pump barrel. The sandproof tube is divided into sections in the middle. Before the motor is connected to the pump, the motor and the plunger pump are respectively connected to half of the sandproof sleeve. First, the upper optical shaft 2 and the plunger pump rod are pulled out beyond the sandproof sleeve. Then, a universal joint is used to connect the upper optical shaft 2 and the plunger pump rod. Finally, a standard coupling is used to connect the two sections of the sandproof sleeve.

[0053] The submersible linear motor well fluid isolation mechanism also includes an ambient temperature and pressure sensor 3 and an armored cable 4 installed at appropriate locations on the sealed cavity shell. The ambient temperature and pressure sensor 3 is used to monitor the temperature and pressure parameters inside and outside the sealed cavity. A universal joint 5 is fixedly connected to the lower end of the upper optical shaft 2, and a mover 6 is fixedly connected to the lower end of the universal joint 5, realizing a universal connection between the upper optical shaft 2 and the mover 6. The stator winding 7 is fixedly connected to the inner wall of the sealed cavity shell, and the mover 6 is coaxially fitted inside the stator winding 7. The stator winding 7 and the mover 6 constitute an electromagnetic structure, located in the motor cavity inside the sealed cavity shell. The armored cable 4 is used to provide power and signal transmission to the stator winding 7.

[0054] Universal joint 5 is ball-head type, which includes a shaft with a ball head and an external thread connecting to the upper optical shaft 2 at the other end. Universal joint 5 also includes a concave seat that wraps around the ball head. The two form a spherical pair that can realize multi-angle rotation and swing. The locking mechanism is a sleeve nut that limits the swing angle and prevents loosening.

[0055] The stator winding 7 and the mover 6 are the moving and stator components of a moving-magnet cylindrical permanent magnet linear motor. The stator winding 7 is segmented, with each segment containing 66 slotted magnetic cores. Flat wire double-panel alpha coils are wrapped within the cores, and the coils are insulated using PTFE varistor tape. The number of stator windings can be adjusted according to thrust requirements. The mover permanent magnet is toroidal and axially magnetized, with magnetically conductive pads between the magnets. All magnets are passed through a micro-magnetic stainless steel rod. The two ends of the mover 6 are connected to the upper optical axis 2 and the lower optical axis 6b, respectively. A micro-magnetic stainless steel tube is used for rubbing between the moving and stator components to protect the permanent magnets.

[0056] Oil groove notch bushings 8 are positioned between the sealing cavity shell and the stator windings 7, between any two adjacent stator windings 7. The distance between two adjacent oil groove notch bushings 8 is equal to the length of the stator winding 7. This is used to straighten the mover and reduce uneven wear. The sealing cavity shell has an oil inlet 10 and an oil outlet 9 located below all the oil groove notch bushings 8. Below the oil inlet 10 and oil outlet 9 is a segmented flange 11 on the lower side of the sealing cavity shell. The lower part of the mover 6 is located inside the segmented flange 11. A second universal joint 5 is fixedly connected to the lower end of the mover 6, and a lower optical shaft 6b is fixed to the lower end of the second universal joint 5. A piston seal 12 is installed above the lower optical shaft 6b below the sealing cavity shell, forming a double-end sealing structure with the upper seal 1. This ensures that the electromagnetic structure is completely enclosed by the sealing cavity shell and isolated from the well fluid environment. The upper optical shaft 2 and the lower optical shaft 6b have the same cross-sectional area to ensure force balance and pressure symmetry during reciprocating motion. The mover 6 is connected to the upper optical axis 2 and the lower optical axis 6b through two universal joints 5. The universal joints 5 have multi-degree-of-freedom rotation capability and can compensate for the coaxiality deviation between adjacent segments of the upper optical axis 2.

[0057] The oil groove notch bushing 8 is made of a wear-resistant, self-lubricating material. Even with slight contact with the stator wear-resistant sleeve 4 on the inner wall of the stator 5, there is no hard friction, further reducing the risk of rotor rubbing. For example, the oil groove notch bushing 8 is made of a polyimide composite material filled with molybdenum disulfide (MoS2), with a friction coefficient ≤0.12 and a wear rate ≤5×10⁻⁶. -7 mm 3 / N·m. Both the mover wear-resistant sleeve 3 and the stator wear-resistant sleeve 4 are coated with diamond-like carbon (DLC) coating, with a hardness ≥ HV2000 and a friction coefficient ≤ 0.10. The sleeve wall thickness is 5.0mm, and its inner wall has 2 to 8 rectangular guide grooves evenly distributed along the axial direction. If 3 grooves are used, the groove depth is 1.5mm, and the groove spacing is 120°. The bottom of the guide grooves retains a minimum wall thickness of 3.0mm, giving the sleeve a slight elastic deformation capability in the radial direction, with an elastic deformation amount ≤ 0.1mm.

[0058] The submersible linear motor well fluid isolation mechanism consists of an upper motor section 1b and a lower motor section 2b. Therefore, the sealing cavity shell is also divided into upper and lower sections. The length of a single section of the submersible linear motor well fluid isolation mechanism does not exceed 10 meters, facilitating transportation and well deployment. Specifically, the assembly of the upper motor section 1b and the lower motor section 2b is as follows:

[0059] The second universal joint 5 includes a universal joint ball head, a universal joint sleeve 5b, and a universal joint ball seat 9b. The shaft portion of the universal joint ball head passes through the universal joint sleeve 5b from top to bottom. The external thread of the shaft portion of the universal joint ball head is screwed into the upper internal thread of the mover 6. The external thread of the mover spindle 7b at the lower part of the mover 6 is screwed into the upper internal thread of the universal joint ball seat 9b. The external thread at the lower part of the universal joint ball seat 9b is screwed into the upper internal thread of the universal joint sleeve 5b. The universal joint ball seat 9b and the spherical surface of the universal joint ball head mate, thereby connecting the mover spindle 7b and the lower optical shaft 6b of the mover 6 at both ends of the second universal joint 5. Then, the upper flange adapter 8b and the segmented lower flange adapter 4b with fluororubber O-ring 3b are fitted and locked together to form the segmented flange 11.

[0060] The oil filling and venting operations are completed through the oil filling port 10 and the venting port. The oil filling port 10 is located at the bottom of the motor and has concentric large and small threads. The small thread fixes a one-way valve that only allows oil to flow in and not out, and the large thread fixes an oil filling nozzle. After the pressure is increased to a slightly positive pressure using a pressure testing pump, the nozzle is replaced with a plug. The oil drain port 9 is used to drain the liquid and is usually sealed by a plug.

[0061] To maintain a slight positive pressure inside the motor cavity and achieve dynamic seal and pressure balance:

[0062] A preload spring 13 is provided on the lower side of the piston seal 12, and a preload spring 13 is provided on the lower side of the spring. Figure 4 The lower cover of the piston seal structure is threadedly connected to the sealing sleeve, becoming part of the sealing cavity shell to support the preload spring 13. The preload spring 13 applies preload to the piston seal 12, making the pressure inside the electromagnetic structure sealing cavity 0.1 MPa higher than the ambient pressure. The pressure test pump gauge displays 0.1 MPa, creating a slightly positive pressure environment. The throughput at both ends of the upper optical shaft 2 is consistent during reciprocating motion, achieving automatic pressure balance; the piston seal 12 can move adaptively, further balancing the pressure difference inside and outside the motor cavity.

[0063] Piston seal 12 includes a piston rod seal that mates with the lower optical shaft, and a piston seal for pressure self-balancing. The piston seal uses a V-group sealing ring 15a made of PTFE+PEEK+FKM. The piston rod seal is the same as seal 1 above, with the sealing ring material being PTFE+40%Bronze+3%MoS2, hardness 62ShD, temperature resistance -200~+260℃, good wear resistance, and resistance to high temperature and high pressure.

[0064] A sand-proof sleeve 14 is fitted and fixed outside the outer shell of the sealing cavity. The sand-proof sleeve 14 is located below the piston seal 12 and wraps around the lower optical shaft to prevent coarse sand particles in the well fluid from entering the sealing area.

[0065] A limit block 15 is fixed to the lower end of the upper optical shaft 2 located below. When the motor reciprocates, the limit block 15 collides with the buffer block 16 at the lower limit position of the stroke. A spring is provided on the lower side of the buffer block 16. The bottom of the spring is supported by the end cover of the motor bottom, which is part of the sealed cavity shell. The spring provides an upward elastic force to the buffer block 16 to absorb the kinetic energy of the mover deceleration. The buffer block 16 is used to limit the axial travel of the upper optical shaft 2 and the mover 6 to prevent collision damage.

[0066] The piston seal 12 has an outer sealing element embedded on its outer circumferential surface. This outer sealing element includes a third support ring 9a, a fifth support ring 13a, and a V-group seal 15a, distributed from top to bottom. The outer sealing element is in contact with the inner wall of the sealing cavity shell. An inner sealing element is embedded on the inner circumferential surface of the piston seal 12. This inner sealing element includes a fourth support ring 10a, a third step seal 11a, a third Y-type sealing ring 14a, a fourth Y-type sealing ring 16a, a fourth step seal 17a, and a second dustproof ring 18a, distributed from top to bottom. The inner sealing element is in contact with the upper optical axis 2 located below. The third support ring 9a and the fourth support ring 10a are set at the same height.

[0067] The wear curves of the sealing material under different pressure differentials are shown in the figure above. At 30 MPa, the wear is more than 10 μm per kilometer, while at 0.1 MPa, the wear is less than 0.1 μm per kilometer. This invention controls the internal and external pressure differential of the motor to 0.1 MPa, reducing wear by 100 times and improving the seal life.

[0068] In this embodiment, the fixed preload spring 13 on the lower side of the piston seal 12 is replaced with an electronically controlled push rod array, and a multi-parameter sensor array and a downhole controller are added to the outer shell of the sealing cavity to form a closed-loop adaptive control system.

[0069] Specifically, a first differential pressure sensor, a second temperature sensor, a stroke encoder, and a current sensor are added to the outer wall of the sealed cavity. The signal output terminals of each sensor are modulated into high-frequency carrier waves via couplers and then injected into the armored cable. The surface end extracts the high-frequency carrier waves from the armored cable via couplers and filters, demodulates the high-frequency carrier waves into raw data, and then connects them to the signal input terminal of the downhole controller. The control signal output terminal of the downhole controller is connected to the drive input terminal of the electric push rod array. The electric push rod array is evenly distributed along the circumference of the lower end face of the piston seal 12. The electric push rods are fixed to the outer shell of the electric control cavity, and each push rod extends and retracts synchronously to apply a uniform axial preload to the piston seal.

[0070] The first differential pressure sensor is used to detect the pressure difference between the inside and outside of the sealed cavity in real time. , i.e., the difference between the motor oil pressure inside the sealed cavity and the ambient well fluid pressure. The second temperature sensor is installed on the surface of the iron core of the stator winding 7 to detect the motor winding temperature T_w in real time. The stroke encoder is integrated into the motor controller to cumulatively record the number of reciprocating strokes N of the motor. The current sensor is connected in series to the power supply circuit of the stator winding 7 to detect the motor operating current I in real time. These four parameters are transmitted to the downhole controller through armored cables.

[0071] The downhole controller is built-in with a sealed health comprehensive index SHI calculation module, which performs feature fusion calculation according to the following formula:

[0072]

[0073] Where, is the nominal slightly positive pressure of 0.1 MPa, T_max is the upper limit of the winding safety temperature of 120 °C, N_life is the number of strokes of the seal design life of 2 million times, and I_rated is the rated current of the motor. When is lower than 0.1 MPa, the term takes 0.5 to avoid negative value interference.

[0074] According to the SHI calculation result, the downhole controller performs a three-level condition determination:

[0075] When SHI ≤ 0.8, it is determined that the sealing system is in a normal state. The downhole controller outputs a first control signal to the electro-control push rod array to maintain the total output force of each push rod as F0, so that the pressure inside the sealed cavity is 0.1 MPa higher than the external pressure of the well fluid, and the motor operates at the rated stroke speed.

[0076] When 0.8 < SHI ≤ 1.3, it is determined that the sealing system is in a warning state. The downhole controller outputs a second control signal to the electro-control push rod array to increase the total output force of each push rod to 1.5F0, so that the pressure inside the sealed cavity is 0.18 MPa higher than the external pressure of the well fluid; at the same time, the downhole controller sends a speed reduction instruction to the motor driver to reduce the stroke speed to 80% of the rated speed.

[0077] When SHI > 1.3, it is determined that the sealing system is in an alarm state. The downhole controller outputs a third control signal to the electro-control push rod array to remove the output force of each push rod; at the same time, it sends a shutdown instruction to the motor driver and uploads the alarm signal to the ground control system.

[0078] The specific structure of the electrically controlled push rod array is as follows: three electrically controlled miniature linear push rods are evenly distributed along the circumference of the lower side of the piston seal 12. The housing of each push rod is fixedly connected to the bottom flange of the sealing cavity housing. The upper end of each push rod's telescopic rod synchronously abuts against the annular pressure plate on the lower end face of the piston seal 12. Each push rod is driven by an independent miniature servo motor to achieve linear extension and retraction using a ball screw pair. The three miniature servo motors are synchronously controlled by the same drive signal to ensure that the extension and retraction of each push rod is consistent. Each push rod's telescopic rod is fitted with a mechanical backup spring. In the event of a failure of the electrical control system, the mechanical backup spring automatically maintains a minimum preload to ensure that the sealing cavity maintains a slight positive pressure of not less than 0.05 MPa.

[0079] The closed-loop effect evaluation is performed as follows: After each control action is executed by the downhole controller, the four parameters ΔP, T_w, N, and I are re-acquired after 30 seconds or 10 reciprocating strokes, and the SHI is recalculated. If the recalculated SHI falls back to ≤0.8, the control is confirmed to be effective, and the current pre-pressure and stroke speed are maintained; if the SHI is still in the range of 0.8 to 1.3, the next level of control is initiated, the pre-pressure is further increased to 2F0, and the stroke speed is further reduced to 60% of the rated speed; if the SHI rises to greater than 1.3, the shutdown protection sequence is triggered.

[0080] For power supply, the power supply unit in the surface control cabinet rectifies and converts 380V AC to high-voltage DC, which is then transmitted to the downhole via armored cables to supply the push rod servo driver, controller, and sensor array. For communication, downlink control commands and uplink status data are transmitted via a power line carrier channel using the power core of the multiplexed armored cable, with OFDM modulation and a communication rate of 115.2kbps. An RS-485 differential bus is also provided as a redundant backup channel, and both channels use the Modbus push rod RTU unified protocol. When the power line carrier is interrupted due to cable insulation deterioration, the RS-485 bus seamlessly takes over. If both wired channels are interrupted, the downhole controller enters autonomous operation mode, continuing to perform SHI classification judgment and push rod control according to locally stored default thresholds. Key data is written to local non-volatile memory and uploaded in batches after communication is restored. The ground monitoring system reads the SHI value, sensor values, and push rod status in real time via power line carrier, and supports remote modification of the three-level threshold and control parameters. When the SHI is greater than 1.3 and triggers an alarm, and is not manually confirmed for 30 seconds, the ground system sends an alarm message to the on-duty engineer via SMS gateway.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A submersible linear motor well fluid isolation mechanism, characterized in that, include: Sealed cavity shell; The upper optical axis extends out of the sealed cavity shell at its upper end and is connected to the upper end of the mover at its lower end. The lower optical axis has its upper end connected to the lower end of the mover, and its lower end extends out of the sealed cavity shell. The electromagnetic structure includes a mover and a stator winding. The electromagnetic structure is enclosed inside the sealed cavity shell. When the mover reciprocates, it drives the upper optical axis and the lower optical axis to move synchronously. An upper seal is provided at the upper part of the outer shell of the sealing cavity to seal the upper optical axis; A piston seal is disposed on the lower side of the outer shell of the sealing cavity and is used to seal the lower optical axis; A pressure compensation element is disposed on the lower side of the piston seal to apply pre-pressure to the piston seal, so that the pressure inside the cavity where the electromagnetic structure is located is higher than the external ambient pressure.

2. The submersible linear motor well fluid isolation mechanism according to claim 1, characterized in that, The upper seal, along the axis of the upper optical shaft, is sequentially arranged from the well fluid side to the motor oil side with a first dustproof ring, a first step seal, a first Y-type sealing ring, a first support ring, a second Y-type sealing ring, a second step seal, and a second support ring. The first dustproof ring is located at the top and is used to prevent coarse sand particles and impurities from entering the sealing assembly. The first step seal is a combined seal, including an O-ring and a PTFE slip ring. The lip of the first Y-type sealing ring faces upwards and mates with the first support ring. The lip of the second Y-type sealing ring faces downwards. The second support ring is used for axial positioning and support.

3. The submersible linear motor well fluid isolation mechanism according to claim 1, characterized in that, An outer sealing element is embedded on the outer circumferential surface of the piston seal, the outer sealing element including a third support ring, a fifth support ring and a V-group seal; an inner sealing element is embedded on the inner circumferential surface of the piston seal, the inner sealing element including a fourth support ring, a third step seal, a third Y-type sealing ring, a fourth Y-type sealing ring, a fourth step seal and a second dustproof ring.

4. The submersible linear motor well fluid isolation mechanism according to claim 1, characterized in that, The pressure compensation element is a pre-compression spring. The pre-compression spring applies a pre-pressure that makes the pressure inside the cavity where the electromagnetic structure is located 0.1 MPa greater than the external ambient pressure, thus creating a slightly positive pressure environment.

5. The submersible linear motor well fluid isolation mechanism according to claim 1, characterized in that, The pressure compensation element includes an electrically controlled pushrod array, which is disposed on the lower side of the piston seal and is used to apply an adjustable axial preload to the piston seal. A multi-parameter sensor array and a downhole controller are disposed on the outer shell of the sealing cavity. The multi-parameter sensor array includes a differential pressure sensor, a temperature sensor, a stroke encoder, and a current sensor. The signal output terminals of each sensor are connected to the signal input terminal of the downhole controller via armored cables. The control signal output terminal of the downhole controller is connected to the drive input terminal of the electrically controlled pushrod array, forming a closed-loop adaptive control system. The downhole controller calculates a comprehensive sealing health index based on the data collected by the multi-parameter sensor array and outputs a control signal to the electrically controlled pushrod array according to the threshold conditions of the comprehensive sealing health index to adjust the magnitude of the axial preload.

6. The mechanism according to claim 5, characterized in that, It also includes a power supply and communication system; the power supply system includes a power supply unit in the ground control cabinet, which uses armored cables to supply the push rod servo driver, the downhole controller and the multi-parameter sensor array respectively; the communication system uses a power line carrier channel with multiplexed armored cable power cores to transmit downlink control commands and uplink status data; when communication is interrupted, the downhole controller switches to autonomous operation mode and continues to perform sealing health comprehensive index grading and push rod control according to the locally stored default threshold.

7. The submersible linear motor well fluid isolation mechanism according to claim 1, characterized in that, The upper optical axis and the mover are connected by universal joints, and the lower optical axis and the mover are connected by universal joints. The universal joints are ball-head type and have multi-degree-of-freedom rotation capability, which are used to compensate for the coaxiality deviation between adjacent optical axes.

8. The submersible linear motor well fluid isolation mechanism according to claim 1, characterized in that, The outer shell of the sealing cavity is fitted with a sand-proof sleeve, which is located below the piston seal and is used to prevent coarse sand particles in the well fluid from entering the sealing area.

9. The mechanism according to claim 1, characterized in that, It also includes an oil groove notch bushing, which is disposed between the sealing cavity shell and the stator winding to straighten the mover and reduce uneven wear.

10. The mechanism according to claim 1, characterized in that, The sealed cavity shell is divided into an upper section and a lower section, which are connected by a segmented flange. The length of a single section does not exceed 10 meters. The electromagnetic structure is correspondingly divided into an upper motor section and a lower motor section. Adjacent moving parts are connected by universal joints. The cross-sectional areas of the upper optical shaft and the lower optical shaft are the same.

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