A new type of submersible motor protector

Abstract

The application belongs to the technical field of submersible electric pumps, and particularly relates to a novel submersible motor protector, which comprises two capsule cavities and a settling cavity. The capsule cavities comprise capsule inner cavities and outer cavities. The capsule cavities are in series, and the second-stage capsule cavity and the settling cavity are in parallel. The series relationship is that the capsule inner cavities are not directly communicated, the second-stage capsule inner cavity is communicated with the capsule outer cavity thereof through an overflow valve, and the second-stage capsule outer cavity is communicated with the first-stage capsule inner cavity. The parallel relationship is that the cavities are directly communicated. The novel submersible motor protector increases the oil supply to the thrust cavity and the motor, and is filled with special insulation oil with a density greater than that of well fluid outside. The novel submersible motor protector can be applied to high-temperature oil wells and geothermal projects.

Description

Technical Field

[0001] This invention belongs to the field of submersible electric pump technology, and in particular relates to a novel submersible motor protector. Background Technology

[0002] Existing technology: A submersible electric pump (SAP) is a mechanical oil extraction device used to pump fluids from downhole to the surface. SSPs offer advantages such as large displacement, high head, strong applicability to deviated wells, small wellhead footprint, and ease of management. Currently, SSPs are widely used in oilfields worldwide.

[0003] The downhole components of a submersible electric pump mainly include a submersible motor, a protector, a separator, a centrifugal pump, and a submersible cable. Among these, the protector plays a crucial role in the normal operation of the submersible electric pump unit. This is mainly reflected in the following four aspects: (1) Connecting the motor to the pump housing and shaft and transmitting the motor torque. (2) Bearing the axial force generated when the pump is working. (3) Achieving dynamic sealing of the motor output shaft, preventing well fluid from entering the motor, achieving soft isolation between the motor and the well fluid, and balancing the pressure inside the motor cavity and the outside. (4) As the motor runs for a longer period of time, the motor temperature rises, causing the motor oil in the cavity to expand due to heat. The protector can provide a flexible expansion space for it. When the motor stops working, as the temperature drops, the motor oil in the motor cavity will contract, and the protector can provide sufficient replenishment for it.

[0004] Most submersible pump protectors used in existing oilfields are modular structures, containing a capsule chamber and a settling chamber. Before use, the protector is filled with motor oil. Conventional modular protectors have a mechanical seal between the capsule chamber and the settling chamber to prevent external well fluid from entering the capsule chamber and then continuing to sink, directly entering the settling chamber and causing it to fail. However, due to this mechanical seal, when replenishing oil to the motor, the insulating oil in the capsule chamber can only flow to the outer chamber of the settling chamber. Only when the oil level is higher than the height of the lower compensation pipe in the settling chamber will the motor oil enter the compensation pipe to continue supplying oil downwards. This results in a portion of motor oil always remaining in the outer chamber of the settling chamber, unable to supply oil to the motor, thus reducing the oil supply to the settling chamber.

[0005] Meanwhile, in some special situations, such as when used in high-temperature oil wells, the performance of conventional motor oil will be greatly reduced, its viscosity and lubrication performance will deteriorate, and the oil expansion volume will increase significantly, causing a large amount of motor oil to leak out of the unit during operation. Ultimately, due to the continuous replacement of well fluid and motor oil, the well fluid will sink to the bottom of the protector, causing the protector to fail rapidly.

[0006] The difficulty and significance of solving the above technical problems: Therefore, based on these issues, providing a new type of submersible motor protector that increases the oil supply to the thrust chamber and inside the motor has significant practical value. Summary of the Invention

[0007] The purpose of this application is to provide a novel submersible motor protector that increases the oil supply to the thrust chamber and the motor interior in order to solve the technical problems in the prior art.

[0008] The technical solution adopted in this application embodiment to solve the technical problems existing in the prior art is as follows: A novel submersible motor protector includes two capsule chambers and a settling chamber. Each capsule chamber comprises an inner capsule chamber and an outer capsule chamber, which are connected in series. The second-stage capsule chamber and the settling chamber are connected in parallel. In the series connection, the inner capsule chambers are not directly connected. The inner capsule chamber of the second-stage capsule is connected to its own outer capsule chamber through an overflow valve, and the outer capsule chamber is in turn connected to the inner capsule chamber of the first-stage capsule. In the parallel connection, the inner capsule chambers are directly connected.

[0009] The embodiments of this application may also employ the following technical solutions: In the aforementioned novel submersible motor protector, the capsule cavity is further divided into two stages, with the inner cavities of the capsules separated by a mechanical seal. The outside is connected to the outer cavity of the first-stage capsule through a straight hole channel in the protector head. A first overflow valve controls the channel between the outer cavity and the inner cavity of the first-stage capsule. The inner cavity of the first-stage capsule is connected to the outer cavity of the second-stage capsule through a straight hole channel in the first sealing seat. A second overflow valve controls the channel between the outer cavity and the inner cavity of the second-stage capsule. The inner cavity of the second-stage capsule is connected to the settling chamber.

[0010] In the aforementioned novel submersible motor protector, the capsule cavity is further defined as a space formed by an upper capsule seat, a lower capsule seat, and the capsule itself, and a capsule shaft protector tube is installed within the capsule cavity.

[0011] In the aforementioned novel submersible motor protector, the inner cavity of the first-stage capsule and the outer cavity of the second-stage capsule are connected through an oil passage hole at the bottom of the capsule shaft protector tube.

[0012] In the aforementioned novel submersible motor protector, the settling chamber further includes a second sealing seat, a third sealing seat, a third-stage mechanical seal, and a third-stage outer shell. The settling chamber and the inner cavity of the second-stage capsule are connected in parallel, that is, the inner cavity of the second-stage capsule is directly connected to the settling chamber.

[0013] In the aforementioned novel submersible motor protector, the thrust cavity is further equipped with an upper thrust bearing, a sliding plate, a lower thrust bearing, and a thrust housing located on the outer side. The upper thrust bearing is located above the sliding plate, and the lower thrust bearing is located below the sliding plate, fitting against the end face of the base.

[0014] In the aforementioned novel submersible motor protector, the insulating oil has a density of 1.86~1.91 g / m³, which is greater than the density of the external well fluid.

[0015] One or more technical solutions provided in the embodiments of this application have at least the following beneficial effects: 1. The second-stage capsule cavity and the settling chamber of the protector of the present invention are connected in parallel. The parallel structure means that the upper-stage chamber and the lower-stage chamber are directly connected, which is equivalent to connecting a chamber in parallel in the lower-stage chamber. This structure increases the oil supply of the protector and can meet the breathing volume requirements of high-power motors.

[0016] 2. This invention designs a dedicated settling chamber structure suitable for special insulating oils. This settling chamber does not have inner and outer cavities, making full use of its volume space for oil storage and supply. A mechanical seal is added to the lower part of the settling chamber, and a straight hole channel is reserved in the lower seal seat as an oil passage between the settling chamber and the thrust chamber. This structure, when used with special insulating oils, not only increases the oil supply to the settling chamber but also blocks well fluid, delaying its entry into the thrust chamber. It also avoids the problem of conventional protector settling chambers where the internal oil level is lower than the compensation pipe height, preventing continued oil supply to the thrust chamber and motor.

[0017] 3. In this invention, the inner cavities of the capsules are connected in series, meaning they are not directly connected. The insulating oil in the second-stage capsule flows to the outer cavity of the second-stage capsule through the overflow valve of the first sealing seat, and then enters the inner cavity of the first-stage capsule through the straight hole channel of the first sealing seat. The two capsule cavities are separated by a mechanical seal, preventing direct communication between them. This prevents well fluid from entering the inner cavity of the second-stage capsule when it enters the inner cavity of the first-stage capsule. This structure adds an extra layer of protection, extends the time before external well fluid enters the capsule, and effectively improves the service life of the protector.

[0018] 4. The protector of this invention uses insulating oil with a density greater than that of well fluid. During the operation of the unit, when well fluid enters the protector, it always floats on top of the insulating oil and is difficult to enter the bottom of the protector and the motor. This isolates the well fluid from the motor windings and effectively prevents external well fluid from entering the protector and continuously descending, thus ensuring that the insulating oil inside the motor can be kept away from the external well fluid for a long time, effectively extending the life of the unit.

[0019] 5. The insulating oil used in the novel submersible pump protector of this invention is perfluoropolyether insulating oil (PFPE), a synthetic polymer that is liquid at room temperature. It possesses excellent lubrication and insulation properties, as well as high density, non-flammability, and high-temperature resistance. This insulating oil is mainly used in the automotive manufacturing industry, textile printing and dyeing industry, and high-temperature applications. Currently, its application is limited in the domestic submersible pump industry. The protector of this invention utilizes the characteristics of perfluoropolyether insulating oil and is specially designed for high-temperature well conditions or geothermal projects. In contrast, existing combined protectors use specialized motor oil, which, when used in high-temperature wells or geothermal projects, will denature and overflow due to excessive temperature, significantly shortening the protector's lifespan. Furthermore, the structure of existing combined protectors is only suitable for situations where the motor oil density is lower than the well fluid, and cannot use perfluoropolyether insulating oil. The novel protector of this invention modifies the structure to effectively address these conditions. Attached Figure Description

[0020] The technical solutions of the embodiments of this application will be further described in detail below with reference to the accompanying drawings. However, it should be understood that these drawings are designed for illustrative purposes only and are not intended to limit the scope of this application. In addition, unless otherwise specified, these drawings are only intended to conceptually illustrate the structural construction described herein and are not necessarily drawn to scale.

[0021] Figure 1 This is a schematic diagram of the structure of a new type of submersible motor protector; Figure 2 This is a schematic diagram of the protector capsule cavity structure; Figure 3 This is a schematic diagram of the settling chamber structure of the protector.

[0022] In the picture: 1 – Protector head; 2a – First-stage housing; 2b – Second-stage housing; 2c – Third-stage housing; 3 – Protective shaft tube; 4a – First-stage capsule inner cavity; 4b – Second-stage capsule inner cavity; 5 – Upper capsule seat; 6 – Capsule; 7 – Capsule protective shaft tube; 8 – Lower capsule seat; 9a – First sealing seat; 9b – Second sealing seat; 9c – Third sealing seat; 10a – First-stage mechanical seal; 10b – Second-stage mechanical seal; 10c – Third-stage mechanical seal; 11a – First relief valve; 11b – Second relief valve; 12 – Settling chamber; 13 – Upper thrust bearing; 14 – Slide plate; 15 – Lower thrust bearing; 16 – Thrust housing; 17 – Thrust chamber; 18 – Base; 19 – Protector shaft. A – Straight hole channel for protector head; B – External cavity of first-stage capsule; C – Straight hole channel for first-stage sealing seat; D – External cavity of second-stage capsule; E – Straight hole channel for second-stage sealing seat; F – Straight hole channel for third-stage sealing seat; i – Oil passage hole for upper capsule seat; j – Oil passage hole at the bottom of capsule shaft protector tube. Detailed Implementation

[0023] The capsule cavities are connected in series, meaning the two capsule cavities are not directly connected. The insulating oil in the second-stage capsule cavity flows to the outer cavity of the second-stage capsule through the overflow valve of the first sealing seat, and then enters the first-stage capsule cavity through the straight hole channel of the first sealing seat. The two capsule cavities are separated by a mechanical seal.

[0024] The capsule chamber and the settling chamber are connected in parallel, meaning that there is no mechanical seal separating the capsule chamber and the settling chamber; they are directly connected internally. This is equivalent to having an additional capsule chamber connected in parallel within the settling chamber to increase the oil supply of the protector.

[0025] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0026] Example 1 A novel submersible motor protector includes two capsule chambers and a settling chamber. Each capsule chamber comprises an inner capsule chamber and an outer capsule chamber, which are connected in series. The second-stage capsule chamber and the settling chamber are connected in parallel. In the series connection, the inner capsule chambers are not directly connected. The inner capsule chamber of the second-stage capsule is connected to its own outer capsule chamber through an overflow valve, and the outer capsule chamber is in turn connected to the inner capsule chamber of the first-stage capsule. In the parallel connection, the inner capsule chambers are directly connected.

[0027] Example 2 Based on Example 1, the motor protector structure is in the form of BSBPL, where B represents the capsule chamber, S represents two chambers connected in series, P represents two chambers connected in parallel, and L represents the settling chamber. That is, it consists of two capsule chambers connected in series, and then connected in parallel with a settling chamber. The two capsule chambers are separated by a mechanical seal, and the inner cavity of the latter capsule chamber is directly connected to the settling chamber. The BSBPL structure greatly increases the amount of oil supplied by the protector to the thrust chamber and the inside of the motor.

[0028] like Figures 1-3 As shown, the novel submersible motor protector of this embodiment is internally filled with insulating oil. The main structural parts of the protector include a protector head 1, a shell 2, a capsule cavity 4, a sealing seat 9, a mechanical seal 10, a settling chamber 12, a thrust chamber 17, a base 18, and a protector shaft 19. Two capsule cavities 4 are connected in series. The capsule cavity has two stages. The capsule cavity closer to the protector head 1 is called the first-stage capsule cavity 4a, and the other capsule cavity is called the second-stage capsule cavity 4b. The two capsule cavities are not connected and are separated by a mechanical seal. The first-stage capsule cavity 4a connects to the outer cavity D of the second-stage capsule cavity 4b. Whether the outer cavity D of the second-stage capsule cavity 4b is connected to the second-stage capsule cavity 4b is controlled by a second overflow valve 11b. The second-stage capsule cavity 4b is directly connected to the settling chamber 12.

[0029] Each capsule cavity 4 consists of an upper capsule seat 5, a capsule 6, a capsule shaft protector tube 7, and a lower capsule seat 8. The volume space inside the capsule 6 is called the capsule inner cavity, and the capsule shaft protector tube 7 is installed in the capsule inner cavity.

[0030] The first-stage capsule cavity 4a and the second-stage capsule cavity 4b are connected in series and separated by a second-stage mechanical seal 10b, preventing direct communication between the two capsule cavities. This extends the time for external well fluid to enter the second-stage capsule cavity 4b, thus improving the lifespan of the protector. The outer cavity of the first-stage capsule cavity is in communication with the external well fluid.

[0031] The settling chamber 12 is composed of a second sealing seat 9b, a third sealing seat 9c, a third-stage mechanical seal 10c, and a shell 2c. The settling chamber 12 and the inner cavity 4b of the second-stage capsule are connected in parallel. That is, there is no mechanical seal separating the inner cavity 4b of the second-stage capsule from the settling chamber 12. The inner cavity 4b of the second-stage capsule is directly connected to the settling chamber 12, which is equivalent to increasing the spatial volume of the settling chamber. The insulating oil of the inner cavity of the upper-stage capsule and the settling chamber can flow together to the thrust chamber and the motor, which can increase the oil storage capacity of the protector.

[0032] Furthermore, the settling chamber is not divided into inner and outer chambers, but consists only of the outer shell and the cavity space between the upper and lower sealing seats, effectively increasing the oil storage capacity inside the protector and meeting the breathing capacity requirements of high-power motors. During use, the insulating oil always sinks to the bottom of the settling chamber.

[0033] The thrust chamber 17 contains an upper thrust bearing 13, a sliding plate 14, a lower thrust bearing 15, and a thrust housing 16. The upper thrust bearing 13 is located above the sliding plate 14 and bears the upward axial force during unit startup. The lower thrust bearing 15 is located below the sliding plate, fitting against the end face of the base 18, and bears the axial force transmitted from the pump during unit operation.

[0034] The perfluoropolyether insulating oil has a density of 1.86~1.91 g / m³, which is greater than that of the external well fluid. It is non-flammable, has a decomposition temperature of 350℃, high temperature resistance, and good insulation and lubrication properties. The insulating oil serves to isolate, lubricate, and regulate the pressure difference between the inside and outside of the unit. Because the insulating oil with a density greater than that of the external well fluid is injected inside the submersible motor protector, when the protector is running, the well fluid floats above the insulating oil inside the protector due to the density difference, preventing it from entering the bottom of the protector and the inside of the motor. This effectively protects the motor insulation and bearings. Simultaneously, the insulating oil has a relatively small coefficient of thermal expansion, resulting in less overflow at high temperatures, significantly reducing the risk of oil shortage inside the protector. Therefore, it can be applied to high-temperature oil wells and geothermal projects.

[0035] Work process: Under normal circumstances, the submersible motor protector operates primarily by fulfilling the principle of "breathing," enabling the motor to achieve pressure balance with the external environment. The working principle of the new submersible motor protector is as follows: The process of the protector "calling out": After the protector is connected to the motor, the inside of the protector and the motor is filled with insulating oil. During the operation of the unit, the motor windings heat up, causing the temperature of the insulating oil to rise. The oil expands due to heat, and the insulating oil in the motor flows through the protector base 18, thrust chamber 17, third sealing seat straight hole channel F, settling chamber 12, and then through the second sealing seat straight hole channel E to the inner cavity 4b of the second-stage capsule. Due to the sealing of the second-stage mechanical seal 10b, the oil pressure increases. When the oil pressure is greater than the opening pressure of the second relief valve 11b, the second relief valve 11b opens, and the insulating oil flows through the relief valve. The oil enters the outer cavity D of the second-stage capsule. At this time, the insulating oil flows from the inside of the capsule to the outside. As the insulating oil in the outer cavity D accumulates, the expanding insulating oil continues to enter the inner cavity 4a of the first-stage capsule along the straight hole channel C of the first sealing seat. The first-stage mechanical seal 10a continues to seal the insulating oil in the cavity of the first-stage capsule. When the oil pressure is greater than the opening pressure of the first overflow valve 11a, the first overflow valve opens, and the lubricating oil enters the outer cavity B of the inner cavity 4a of the first-stage capsule. Finally, the excess insulating oil is discharged along the straight hole channel A on the protector head, achieving the effect of balancing the internal and external pressure of the unit.

[0036] The protector's "suction" process: When the motor needs oil replenishment, the insulating oil in the protector base 18 is first sucked into the motor cavity. Due to the pressure difference between the inside and outside, the insulating oil in the thrust chamber 17 and settling chamber 12 flows downwards for replenishment. The capsule in the second-stage capsule cavity 4b contracts, and the insulating oil inside flows into the settling chamber 12. Correspondingly, the insulating oil in the first-stage capsule cavity 4a enters the outer cavity D of the second-stage capsule cavity 4b through the straight hole channel C of the first sealing seat. External well fluid enters the outer cavity B of the first-stage capsule cavity 4a through the straight hole channel A of the protector head, achieving pressure balance between the inside and outside of the unit.

[0037] Example 3 Based on Example 2, an oil passage hole i is opened on the upper capsule seat 5. The oil passage hole i of the upper capsule seat connects the inner cavity of the capsule with the inside of the protective shaft tube 3. Four oil passage holes j are opened at the bottom of the capsule protective shaft tube 7. The oil passage holes j at the bottom of the capsule protective shaft tube connect the inner cavity of the capsule with the outer cavity of the next level. Its function is to connect with the oil passage of the next chamber.

[0038] During long-term operation, external well fluid may leak into the capsule cavity of the novel submersible motor protector due to mechanical seal leakage. The following is an example... Figure 2 and Figure 3 Taking this as an example, we will explain the working principle of the protector capsule cavity and the settling cavity.

[0039] like Figure 2 As shown in the figure, the arrows represent the flow process of the well fluid. First, when leakage occurs due to the mechanical seal, the well fluid enters the capsule cavity along the gap between the protective shaft tube 3 and the protector shaft 19. Since the density of the insulating oil in the capsule cavity is greater than that of the well fluid, the well fluid always floats above the lubricating oil. As the running time increases, the insulating oil in the capsule cavity 4 is gradually consumed, and the well fluid enters the capsule cavity through the oil passage hole i of the upper capsule seat, and then enters the next stage cavity through the oil passage hole j at the bottom of the capsule protective shaft tube.

[0040] like Figure 3 As shown, after the failure of the first two capsule chambers, the well fluid will enter the settling chamber 12 through the straight hole channel of the second sealing seat. Similarly, due to the density difference, the well fluid will first float above the lubricating oil. When the insulating oil in the settling chamber is consumed, the well fluid will flow to the straight hole channel F of the third sealing seat and then enter the thrust chamber of the protector.

[0041] In summary, this invention provides a novel submersible motor protector that increases the amount of oil supplied to the thrust chamber and the motor interior by the protector.

[0042] The above embodiments have provided a detailed description of the present invention, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent variations and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A novel submersible motor protector, characterized in that: The novel submersible motor protector includes two capsule chambers and a settling chamber. The settling chamber is a single cavity without inner or outer chambers, and its bottom straight-hole oil passage connects to the thrust chamber. Each capsule chamber includes an inner capsule chamber and an outer capsule chamber, which are connected in series. The second-stage capsule chamber is connected in parallel with the settling chamber, without mechanical seal separation. The series connection means that the inner capsule chambers are not directly connected and are separated by a mechanical seal. The inner capsule chamber of the second-stage capsule is connected to its own outer capsule chamber through an overflow valve, and the outer capsule chamber is also connected to the inner capsule chamber of the first-stage capsule. The parallel connection means that they are directly connected internally. The inner capsule chamber of the first-stage capsule and the outer capsule chamber of the second-stage capsule are connected through an oil passage at the bottom of the capsule shaft tube. The protector is filled with insulating oil with a density of 1.86~1.91 g / m³. 3 The density is greater than that of the external well fluid. The capsule cavity is divided into two stages, with the inner cavities of the capsule separated by a mechanical seal. The outside is connected to the outer cavity of the first-stage capsule through a straight hole channel of the protector head. A first overflow valve controls the channel between the outer cavity and the inner cavity of the first-stage capsule. The inner cavity of the first-stage capsule is connected to the outer cavity of the second-stage capsule through a straight hole channel of the first sealing seat. A second overflow valve controls the channel between the outer cavity and the inner cavity of the second-stage capsule. The inner cavity of the second-stage capsule is connected to the settling chamber. The capsule cavity is a space enclosed by an upper capsule seat, a lower capsule seat, and the capsule itself, and a capsule shaft protector tube is installed inside the capsule cavity. The settling chamber includes a second sealing seat, a third sealing seat, a third-stage mechanical seal, and a third-stage outer shell. The settling chamber is connected in parallel with the inner cavity of the second-stage capsule, meaning that the inner cavity of the second-stage capsule is directly connected to the settling chamber.

2. The novel submersible motor protector according to claim 1, characterized in that: The thrust cavity contains an upper thrust bearing, a sliding plate, a lower thrust bearing, and a thrust housing located on the outside. The upper thrust bearing is located above the sliding plate, and the lower thrust bearing is located below the sliding plate, fitting against the end face of the base.

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