System and method for handling thrust loads in axial flow pump

Abstract

A technique facilitates handling of thrust loads in a pump, such as a submersible pump which may be used in an electric submersible pumping system. For example, the submersible pump may comprise a plurality of pump stages disposed within an outer pump housing. Individual pump stages of the plurality of pump stages each have an impeller and a diffuser with the impeller being rotatable relative to the diffuser via a shaft. Each individual pump stage also comprises a stage thrust bearing assembly to handle thrust loads generated during operation of the submersible pump via rotation of the impellers.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of Singapore Provisional Application No. 10202300346T filed Feb. 10, 2023, the entire contents of which are herein incorporated by reference in their entirety.BACKGROUND

[0002] In many hydrocarbon well applications, electric submersible pumping (ESP) systems are used for pumping fluids, e.g. hydrocarbon-based fluids. For example, the ESP system may be conveyed downhole and used to pump oil from a downhole wellbore location to a surface collection location along a production tubing. The ESP system comprises various components, including a submersible pump, a submersible motor, and a motor protector. The submersible pump has sequential stages with each stage including an impeller and a cooperating diffuser. The impellers are mounted on a shaft and rotated relative to the diffusers to create an axial flow of fluid through the submersible pump. Downthrust created by the impellers is transferred to the shaft and ultimately to a thrust bearing located in the motor protector. A disadvantage of this construction is that a failure at the thrust bearing rapidly leads to submersible pump failure. Additionally, to accommodate assembly and operational shaft deflections this type of submersible pump is constructed with high endplay.SUMMARY

[0003] In general, a system and methodology facilitate handling of thrust loads in a pump, such as a submersible pump which may be used in an electric submersible pumping system. For example, the submersible pump may comprise a plurality of pump stages disposed within an outer pump housing. Individual pump stages of the plurality of pump stages each have an impeller and a diffuser with the impeller being rotatable relative to the diffuser via a shaft. Each individual pump stage also comprises a stage thrust bearing assembly to handle thrust loads generated during operation of the submersible pump via rotation of the impellers.

[0004] However, many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein, and:

[0006] FIG. 1 is a schematic illustration of a well system comprising an example of a submersible pump, the submersible pump being incorporated into an electric submersible pumping system positioned in a borehole, e.g. a wellbore, according to an embodiment of the disclosure;

[0007] FIG. 2 is a cross-sectional view of a portion of one example of a submersible pump, according to an embodiment of the disclosure;

[0008] FIG. 3 is an orthogonal view of an example of a thrust bearing runner which may be used in the submersible pump illustrated in FIG. 2, according to an embodiment of the disclosure;

[0009] FIG. 4 is a cross-sectional view of a portion of another example of a submersible pump, according to an embodiment of the disclosure;

[0010] FIG. 5 is a cross-sectional view of a portion of another example of a submersible pump, according to an embodiment of the disclosure;

[0011] FIG. 6 is an orthogonal view of an example of a thrust bearing which may be used in the submersible pump illustrated in FIG. 5, according to an embodiment of the disclosure;

[0012] FIG. 7 is a different orthogonal view of the thrust bearing illustrated in FIG. 6, according to an embodiment of the disclosure;

[0013] FIG. 8 is an orthogonal view of an example of a thrust bearing runner which may be used in the submersible pump illustrated in FIG. 5, according to an embodiment of the disclosure;

[0014] FIG. 9 is an orthogonal view of an example of a bearing sleeve which may be used in the submersible pump illustrated in FIG. 5, according to an embodiment of the disclosure;

[0015] FIG. 10 is a cross-sectional view of an example of an additional thrust bearing assembly which may be used in a submersible pump, according to an embodiment of the disclosure;

[0016] FIG. 11 is an orthogonal view of an example of a thrust bearing which may be used in the thrust bearing assembly illustrated in FIG. 10, according to an embodiment of the disclosure; and

[0017] FIG. 12 is an orthogonal view of an example of a thrust bearing runner which may be used in the thrust bearing assembly illustrated in FIG. 10, according to an embodiment of the disclosure.DETAILED DESCRIPTION

[0018] In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and / or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

[0019] The present disclosure generally relates to a system and methodology which facilitate handling of thrust loads in a pump. The pump may be an axial flow pump in the form of a submersible pump, e.g. a submersible pump which may be used in an electric submersible pumping system. According to an embodiment, the submersible pump comprises a plurality of pump stages disposed within an outer pump housing. The pump stages each have an impeller and a diffuser arranged such that the impellers are rotatable relative to the diffusers via a shaft. Additionally, individual pump stages of the plurality of pump stages each comprise a stage thrust bearing assembly to handle thrust loads generated during operation of the submersible pump via rotation of the impellers. In some embodiments, all of the pump stages are constructed as the individual pump stages having stage thrust bearing assemblies. However, other embodiments may incorporate the stage thrust bearing assemblies in a portion of the overall number of pump stages.

[0020] According to an embodiment, the submersible pump comprises floater type pump stages where the generated downthrust is handled by at least some of the floater type pump stages. For example, the stage thrust bearing assemblies may be incorporated into floater type, axial flow pump stages rather than relying on a conventional motor protector thrust bearing. The floater bearing architecture facilitates placement of the stage thrust bearing assemblies in line with the flow passage of fluid being moved / pumped through the submersible pump. This type of architecture provides better heat dissipation and reduces the risk of damage to the thrust bearings due to overheating.

[0021] Referring generally to FIG. 1, an example of a pump 20, e.g. a submersible, floater type pump, is illustrated as deployed in a well-related application. However, the illustrated embodiment is simply provided as an example of numerous potential embodiments that may utilize the thrust bearing assemblies positioned in individual pump stages as described herein. Referring again to FIG. 1, pump 20 may be deployed in a submersible pumping system 22, e.g. an electric submersible pumping system.

[0022] The submersible pumping system 22 may comprise a variety of components depending on the particular well application and / or environment in which it is used. In addition to the submersible pump 20, other components of submersible pumping system 22 may comprise at least one submersible motor 24 and, in some embodiments, a motor protector 26. Even though the motor protector 26 may not be needed for countering thrust loading in certain embodiments described herein, the motor protector 26 may be used for pressure balancing of the internal motor fluid of submersible motor 24 with respect to the surrounding environment. The submersible pump 20, submersible motor 24, and motor protector 26 are coupled together into electric submersible pumping (ESP) system 22 in a manner such that submersible motor 24 may be selectively operated to power the submersible pump 20. In some embodiments, a plurality of submersible pumps 20, e.g. tandem submersible pumps, may be employed.

[0023] The submersible pumping system 22 may be deployed in a wellbore 28 drilled into a geologic formation 30 containing, for example, desirable production fluids such as hydrocarbon-based fluids. In some applications, the electric submersible pumping system 22 may be positioned vertically in a vertical section of wellbore 28 but in other applications electric submersible pumping system 22 may be positioned in a deviated, e.g., horizontal, sectional wellbore 28. It should be noted wellbore 28 may comprise various types of boreholes used for production, injection, or other pumping operations. In some applications, the wellbore 28 may be lined with a wellbore casing 32 which may be perforated with a plurality of perforations 34 extending through the casing 32 and into the surrounding formation 30. The perforations 34 enable flow of fluids between the surrounding formation 30 and the wellbore 28.

[0024] The submersible pumping system 22 may be deployed downhole into wellbore 28 via a conveyance 36. The conveyance 36 may have a variety of configurations and may comprise a tubing 38, e.g., coiled tubing or production tubing. However, other suitable conveyances, such as wireline or slick line, also may be used to deploy submersible pumping system 22. The conveyance 36 may be coupled with submersible pumping system 22 by an appropriate connector 40 that may comprise or may be coupled with a discharge head 42 which receives and discharges fluid pumped by submersible pump 20.

[0025] Electric power may be provided to submersible motor 24 via a power cable 44 which extends along conveyance 36 and submersible pumping system 22 for connection with submersible motor 24. The submersible motor 24, in turn, powers submersible pump 20 which then draws in fluid from wellbore 28 through a pump intake 46. By way of example, the submersible motor 24 may power submersible pump 20 via a pump shaft used to rotate at least one impeller.

[0026] Within submersible pump 20, for example, a plurality of impellers may be rotated to pump fluid from intake 46, through submersible pump 20, and out through the discharge head 42. The discharged fluid may be directed along an interior of tubing 38 (or along another suitable flow path) to a desired location, such as a collection location at the surface. However, various other components and system configurations may be utilized in a variety of pumping operations and environments.

[0027] Referring generally to FIG. 2, a cross-sectional portion of one example of pump 20 is illustrated in the form of a submersible pump. In this embodiment, the submersible pump 20 comprises a plurality of pump stages 48 distributed along an interior of the submersible pump 20. In FIG. 2, a relatively small number of the actual pump stages 48 is illustrated to facilitate explanation; however pump stages 48 would tend to be distributed along a substantial length of the submersible pump 20. As illustrated, the submersible pump 20 also comprises an outer pump housing 50 which may be tubular in shape and house the pump stages 48. A shaft 52 may be rotatably mounted within the outer pump housing 50 generally along a central pump axis of the submersible pump 20.

[0028] The pumps stages 48 may comprise a plurality of pairs of cooperating diffusers 54 and impellers 56 in which an individual impeller 56 is rotatably mounted within the corresponding diffuser 54 within each pump stage 48. The impellers 56 are rotated via shaft 52 relative to their corresponding diffusers 54 so as to create an axial flow of fluid through the submersible pump 20 along a flow passage 57. Individual pump stages 48 (and sometimes all of the pump stages 48) each further include a stage thrust bearing assembly 58. The stage thrust bearing assemblies 58 may be constructed to absorb downthrust loading, upthrust loading, and / or radial loading.

[0029] Each stage thrust bearing assembly 58 may comprise a thrust bearing 60 and a thrust bearing runner 62 which is rotatable against the thrust bearing 60. The thrust bearing 60 may be formed from a hard, wear resistant material such as a suitable ceramic material. Similarly, the thrust bearing runner 62 may be made from a wear resistant material to enhance the longevity of the stage thrust bearing assembly 58.

[0030] In the embodiment illustrated, the thrust bearing 60 is locked in place with respect to the corresponding diffuser 54. For example, the thrust bearing 60 may be locked with respect to the surrounding diffuser 54 via a retaining ring 64. Additionally, the thrust bearing runner 62 is locked to the shaft 52 and thus rotates with the shaft 52. By way of example, the thrust runner bearing 62 may be keyed directly onto the shaft 52 and thus rotationally locked with respect to the shaft 52. In some embodiments, the thrust bearing runner 62 may be secured to the corresponding impeller 56.

[0031] The stage thrust bearing assembly 58 also may comprise a sleeve 66. By way of example, the sleeve 66 may be positioned radially between thrust bearing 60 and shaft 52. In this manner, the sleeve 66 cooperates with thrust bearing 60 so as to serve as a radial bearing resisting radial loading. Simultaneously, the thrust bearing 60 serves as a thrust bearing able to resist downthrust loading and upthrust loading which occur during operation of the submersible pump 20 as a result of the rotating impellers 56.

[0032] The submersible pump 20 also may comprise a variety of other components and features depending on the parameters of a given operation and on environmental considerations. In the example illustrated, the impellers 56 / diffusers 54 may be secured in position within outer pump housing 50 via a suitable support ring 68 held in place along shaft 52 via a lock ring 70. In some embodiments, lubrication grooves 72 may be positioned, e.g. positioned radially, along thrust bearing runner 62, as illustrated in FIG. 3. The lubrication grooves 72 allow for a hydrodynamic fluid film to be developed at the interface between the thrust bearing runner 62 and the thrust bearing 60. Various additional and / or other components and features may be utilized in submersible pump 20.

[0033] Referring generally to FIG. 4, another embodiment of submersible pump 20 is illustrated. In this example, the pump stages 48 are constructed as floater type, axial flow stages. However, the stage thrust bearing assemblies 58 are constructed with thrust handling bearing surfaces formed via cladding, sometimes referred to as additive manufacturing.

[0034] As illustrated, each stage thrust bearing assembly 58 may comprise a first bearing surface formed via a first cladding 74 and a second bearing surface formed via a second cladding 76. By way of example, the first cladding 74 may be positioned directly on the impeller 56 and the second cladding 76 may be positioned directly on a corresponding diffuser 54 or other suitable bearing housing feature. The cladding 74, 76 is formed from a hard material, e.g. tungsten carbide, which may be directly attached onto the impeller 56 and corresponding diffuser / bearing housing at the desired downthrust loading region. By way of example, the cladding 74, 76 may be directly welded or otherwise secured at the appropriate locations. This approach enables formation of thrust bearings at multiple locations, e.g. at multiple stages, along submersible motor 20 without requiring a special locking mechanism for holding the thrust bearings in place.

[0035] Referring generally to FIG. 5, another embodiment of submersible pump 20 is illustrated. In this embodiment, the submersible pump 20 includes pump stages 48 having an integrated thrust and radial bearing architecture. For example, at least some of the pump stages 48 may comprise a corresponding stage thrust bearing assembly 58 having thrust bearing 60 secured with respect to the surrounding diffuser 54 via retainer ring 64. As further illustrated in FIGS. 6 and 7, this embodiment of thrust bearing 60 may comprise a radial bearing surface 78, a downthrust bearing surface 80, and an upthrust bearing surface 82 oriented to handle radial loading, downthrust loading, and upthrust loading, respectively.

[0036] Additionally, this embodiment of bearing assembly 58 comprises thrust runner 62 positioned to rotate against downthrust bearing surface 80. The thrust runner 62 may be rotationally secured to shaft 52 via, for example, a key and keyway coupling mechanism. An example of a keyway 84 is illustrated as formed in thrust runner 62 in FIG. 8. A similar keyway 84 with a corresponding key may be used to rotationally lock thrust bearing 60 to the surrounding diffuser 54 (see FIG. 7). The thrust runner 62 may be held in position longitudinally by a suitable spacer ring 86. In some embodiments, a sacrificial thrust washer 88 may be positioned between the bottom of each impeller 56 and the next adjacent diffuser 54. With this type of arrangement, a gap 90 may be located between the spacer ring 86 and the next adjacent impeller 56 to allow for wear of the sacrificial thrust washer 88.

[0037] As illustrated, a bearing sleeve 92 may have a portion located radially between the shaft 52 and the thrust bearing 60. The bearing sleeve 92 works in cooperation with the thrust bearing 60 to provide support against radial loading. The bearing sleeve 92 may comprise a radially expanded integral upthrust runner 94 (also see FIG. 9) having an upthrust surface 95 positioned so as to act against upthrust bearing surface 82 of thrust bearing 60. In some embodiments, the bearing sleeve 92 also may comprise a suitable mechanism, e.g. a keyway 84 for use with a suitable key, to rotationally lock the bearing sleeve 92 onto shaft 52. This type of embodiment of stage thrust bearing assembly 58 may be employed in each of the pump stages 48 or in a fewer number of individual pump stages 48.

[0038] In some embodiments of submersible pump 20, an additional thrust handling bearing assembly or assemblies 96 may be employed, as illustrated in FIG. 10. For example, additional thrust handling bearing assemblies 96 may be introduced to handle the thrust acting on the shaft 52 due to pump generated boost pressure. Such a thrust handling bearing assembly or assemblies 96 may be located within the submersible pump 20 at the top, middle, and / or bottom section of the stack of pump stages 48 to help handle the downthrust. The thrust handling bearing assemblies 96 may be mounted to allow for fluids to flow about the outer diameter of the bearing, as indicated by arrow 98, to facilitate cooling of the bearing(s) 96.

[0039] As illustrated in FIG. 10, the thrust handling bearing assembly 96 may comprise a thrust bearing 100 (see also FIG. 11) held in place with respect to a portion of the pump body structure 102 by anti-rotation pins 104 or other suitable retention mechanism. Additionally, the thrust bearing 100 may be held in place longitudinally via a retaining ring 106 or other suitable mechanism. A thrust bearing runner 108 (see also FIG. 12) is connected to shaft 52 for rotation with shaft 52 against thrust bearing 100. By way of example, the thrust bearing runner 108 may be secured to shaft 52 via an internal retaining ring 110 or other suitable retaining mechanism. In some embodiments, the thrust bearing runner 108 also may be rotationally secured via a suitable mechanism such as a key and keyway 84 arrangement. In the example illustrated, the thrust bearing runner 108 is held in position longitudinally via a cooperating two-piece ring 112 which, in turn, may be secured longitudinally along shaft 52 via a retaining ring 114.

[0040] Depending on the parameters of a given application and / or environment, embodiments described herein may utilize various structures to achieve the desired handling of thrust loads. For example, the number and arrangement of stage thrust bearing assemblies 58 may vary and may be positioned through some or all of the pump stages 48. In some embodiments, one or more of the additional thrust bearing assemblies 96 may be employed to assist in handling the thrust loading produced during operation of the submersible pump 20.

[0041] Additionally, the overall size and structure of pump 20 and / or submersible pumping system 22 may be adjusted to accommodate many types of pumping applications. For example, the submersible pumping system 22 may be in the form of an electric submersible pumping system combined with other components for use in a wellbore or other type of borehole. Similarly, the number and arrangement of pump stages 48 of submersible pump 20 may vary. The style of pump stages 48 may be in the form of axial flow stages, radial flow stages, mixed flow stages, or other suitable pump stage styles to achieve the desired flow in a given pumping environment.

[0042] Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.

Claims

1. A system for pumping, comprising:a submersible pump constructed for use in an electric submersible pumping system, the submersible pump comprising a plurality of pump stages disposed within an outer pump housing, individual pump stages of the plurality of pump stages each comprising an impeller and a diffuser, the impeller being rotatable relative to the diffuser via a shaft, the individual pump stages each comprising a stage thrust bearing assembly to handle thrust loads generated during operation of the submersible pump.

2. The system as recited in claim 1, wherein all of the plurality of pump stages comprise the individual pump stages incorporating the stage thrust bearing assemblies.

3. The system as recited in claim 1, wherein the stage thrust bearing assembly comprises a thrust bearing and a thrust bearing runner rotatable against the thrust bearing.

4. The system as recited in claim 3, wherein the stage thrust bearing assembly further comprises a sleeve disposed within the thrust bearing, the thrust bearing working in cooperation with the sleeve to serve as both a radial bushing and a downthrust bearing.

5. The system as recited in claim 3, wherein the thrust bearing is secured to the diffuser.

6. The system as recited in claim 5, wherein the thrust bearing runner is secured to the shaft.

7. The system as recited in claim 3, wherein the thrust bearing runner comprises lubrication grooves.

8. The system as recited in claim 1, wherein the stage thrust bearing assembly comprises bearing surfaces formed of cladding disposed on at least a surface of the impeller.

9. The system as recited in claim 1, wherein the submersible pump comprises an additional integral thrust bearing assembly separate from the stage thrust bearing assemblies of individual pump stages.

10. A system for pumping, comprising:a submersible pump, the submersible pump having:an outer housing;a plurality of pump stages located within the outer housing, each pump stage having an impeller rotatable within a diffuser;a shaft extending longitudinally through the outer housing, the shaft being coupled to the impeller of each pump stage; anda plurality of stage thrust bearing assemblies arranged such that an individual stage thrust bearing assembly is located in each pump stage of the plurality of pump stages.

11. The system as recited in claim 10, wherein the plurality of pump stages comprises all pump stages located within the outer housing.

12. The system as recited in claim 10, wherein the individual stage thrust bearing assemblies handle downthrust loading, upthrust loading, and radial loading.

13. The system as recited in claim 10, wherein the submersible pump is part of an electric submersible pumping system comprising a submersible motor for powering the submersible pump.

14. The system as recited in claim 10, wherein each stage thrust bearing assembly comprises a thrust bearing and a thrust bearing runner rotatable against the thrust bearing.

15. The system as recited in claim 14, wherein the thrust bearing is secured to the diffuser.

16. The system as recited in claim 14, wherein the stage thrust bearing assembly further comprises a sleeve disposed within the thrust bearing, the thrust bearing working in cooperation with the sleeve to serve as both a radial bushing and a downthrust bearing.

17. The system as recited in claim 14, wherein the thrust bearing runner is secured to the shaft.

18. The system as recited in claim 14, wherein the thrust bearing runner comprises lubrication grooves.

19. The system as recited in claim 10, wherein the stage thrust bearing assembly comprises bearing surfaces formed of cladding disposed on at least a surface of the impeller.

20. The system as recited in claim 10, wherein the submersible pump comprises an additional integral thrust bearing assembly separate from the stage thrust bearing assemblies of individual pump stages.

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