Hybrid magnetic thrust bearing in an electric submersible pump (ESP) assembly

An electric submersible pump (ESP) assembly. The ESP assembly comprises an electric motor, a centrifugal pump, and a hybrid magnetic thrust bearing, wherein the hybrid magnetic thrust bearing is disposed inside the electric motor or disposed inside the centrifugal pump.

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

BACKGROUND

Electric submersible pump (ESP) assemblies are used to artificially lift fluid to the surface in deep wells such as oil or water wells. A typical ESP assembly comprises, from bottom to top, an electric motor, a seal unit, a pump intake, and a centrifugal pump, which are all mechanically connected together with shafts and shaft couplings. The electric motor supplies torque to the shafts, which provides power to the centrifugal pump. The electric motor is isolated from a wellbore environment by a housing and by the seal unit. The seal unit acts as an oil reservoir for the electric motor. The oil functions both as a dielectric fluid and as a lubricant in the electric motor. The seal unit also may provide pressure equalization between the electric motor and the wellbore environment. The centrifugal pump transforms mechanical torque received from the electric motor via a drive shaft to fluid pressure to lift fluid up the wellbore. The electric motor is generally connected to a power source located at the surface of the well using a cable and a motor lead extension. The ESP assembly is placed into the well and usually is inside a well casing. In a cased completion, the well casing separates the ESP assembly from the surrounding formation. Perforations in the well casing allow well fluid to enter the well casing and flow to the pump intake.

DETAILED DESCRIPTION

As used herein, orientation terms “upstream,” “downstream,” “up,” and “down” are defined relative to the direction of flow of well fluid in the well casing. “Upstream” is directed counter to the direction of flow of well fluid, towards the source of well fluid (e.g., towards perforations in well casing through which hydrocarbons flow out of a subterranean formation and into the casing). “Downstream” is directed in the direction of flow of well fluid, away from the source of well fluid. “Down” is directed counter to the direction of flow of well fluid, towards the source of well fluid. “Up” is directed in the direction of flow of well fluid, away from the source of well fluid.

Rotating components of electric submersible pump (ESP) assemblies may be axially supported by thrust bearings. As used herein, axially supporting rotating ESP components means transferring at least part of an axial force (e.g., a force acting in a direction parallel to an axis of rotation of the rotating ESP components) exerted by the rotating components to a housing and/or non-rotating component of the ESP assembly. The axial force may be transferred from the rotating ESP components by one or more drive shafts via one or more thrust bearings to the housing and/or non-rotating components of the ESP assembly. The axial force may be directed downhole or uphole. The axial force may be developed in part by weight of rotating components. The axial force due to weight of rotating components may vary between different well completions according as the ESP assembly is disposed mostly vertically or mostly horizontally in the wellbore. The axial force may be developed in part by a thrust force developed by impellers of a centrifugal pump of the ESP assembly. In some operation regimes of a centrifugal pump the thrust force developed by the impellers may be such that a net uphole force is developed, but typically the net axial force is directed downhole.

Wear and tear on ESP assembly thrust bearings effect the longevity of the ESP assemblies. Premature wear of ESP assembly thrust bearings may entail pulling ESP assemblies for replacement more frequently and lead to increased non-producing down time as well as increased costs related to servicing the ESP assembly at the well site and increased equipment costs. The present disclosure teaches use of hybrid magnetic thrust bearings to extend the service life of thrust bearings and thereby extend the service life of the ESP assemblies. The hybrid magnetic thrust bearings taught herein augment traditional fluid film force with magnetic force. As a result, a surface smoothness tolerance can be relaxed for the bearing surfaces of the hybrid magnetic thrust bearings. This relaxed smoothness tolerance may reduce the cost of manufacturing the bearings. Additionally, clearances between bearing surfaces may be increased, which improves heat transfer due to a greater volume of fluid film between the bearing surfaces. This better heat transfer may allow the ESP assembly to be operated in higher temperature downhole environments than otherwise and/or may extend the service life of the ESP assembly. This greater clearance between the bearing surfaces may further reduce wear on the hybrid magnetic thrust bearings relative to conventional thrust bearings from abrasive particles encountered during ESP assembly operation, for example sand and metal particles entrained in the fluid flowing in the centrifugal pump. As described in more detail with reference toFIG. 5AandFIG. 5Bbelow, the hybrid magnetic thrust bearings taught herein may counteract oscillatory vibrations that sometimes develop in conventional thrust bearings as a result of eccentric wear and may in part correct any eccentric wear which may develop in the hybrid magnetic thrust bearings.

Turning now toFIG. 1, a producing well environment100is described. In an embodiment, the environment100comprises a wellhead101above a wellbore102located at the surface103. A casing104is provided within the wellbore102.FIG. 1provides a directional reference comprising three coordinate axes—an X-axis160where positive displacements along the X-axis160are directed into the sheet and negative displacements along the X-axis160are directed out of the sheet; a Y-axis162where positive displacements along the Y-axis162are directed upwards on the sheet and negative displacements along the Y-axis162are directed downwards on the sheet; and a Z-axis164where positive displacements along the Z-axis164are directed rightwards on the sheet and negative displacements along the Z-axis164are directed leftwards on the sheet. The Y-axis162is about parallel to a central axis of a vertical portion of the wellbore102.

An electric submersible pump (ESP) assembly106is deployed within the casing104and comprises an optional sensor unit108, an electric motor110, a motor head111, a seal unit112, an electric power cable113, a pump intake114, a centrifugal pump116, and a pump outlet118that couples the pump116to a production tubing120. In an embodiment, the ESP assembly106may employ hybrid magnetic thrust bearings in several places, for example in the electric motor110, in the seal unit112, and/or in the centrifugal pump116. While not shown inFIG. 1, in an embodiment, the ESP assembly106comprises a gas separator that may employ one or more hybrid magnetic thrust bearings. The motor head111couples the electric motor110to the seal unit112. The electric power cable113may connect to a source of electric power at the surface103and to the electric motor110. The casing104is pierced by perforations140, and reservoir fluid142flows through the perforations140into the wellbore102. The fluid142flows downstream in an annulus formed between the casing104and the ESP assembly106, is drawn into the pump intake114, is pumped by the centrifugal pump116, and is lifted through the production tubing120to the wellhead101to be produced at the surface103. The fluid142may comprise hydrocarbons such as oil and/or gas. The fluid142may comprise water. The fluid142may comprise both hydrocarbons and water.

Turning now toFIG. 2A, an electric motor200is supported axially by a hybrid magnetic thrust bearing. The electric motor200comprises a rotor202, a stator204, a housing208, and a hybrid magnetic thrust bearing209. The electric motor200may be the electric motor110of the ESP assembly106. The hybrid magnetic thrust bearing209comprises a thrust transfer plate210and a thrust support plate212. The thrust transfer plate210is coupled to the drive shaft206and turns with the drive shaft206. The thrust support plate212is supported by the housing208. Thrust force associated with weight of the rotor202(and possibly thrust force developed by other rotating components of the ESP assembly106) is transferred to the drive shaft206, from the drive shaft206to the thrust transfer plate210, from the thrust transfer plate to the thrust support plate213, and from the thrust support plate212to the housing208.

While a single hybrid magnetic thrust bearing209is illustrated inFIG. 2A, in an embodiment, another hybrid magnetic thrust bearing209may be located in the electric motor200at the top of the motor200. In this case, the hybrid magnetic thrust bearing209would be flipped, with the thrust transfer plate210located closest to the rotor202and the thrust support plate212located away from the rotor202(e.g., above the thrust transfer plate). In this alternate embodiment, the rotor202would be sandwiched between two hybrid magnetic thrust bearings, one hybrid magnetic thrust bearing disposed to support axial thrust directed downhole (e.g., directed axially downwards parallel to the central axis of the drive shaft206) and the other hybrid magnetic thrust bearing disposed to support axial thrust directed uphole (e.g., directed axially upwards parallel to the central axis of the drive shaft206).

The electric motor110may be implemented similar to the electric motor200. In an embodiment, the electric motor200(and electric motor110) may comprise a plurality of rotor and stator stages, whereby to produce more mechanical torque than would be produced by a single rotor and stator pair. In this case, an electric motor110,200comprising a plurality of rotor and stator stages may be associated with a single hybrid magnetic thrust bearing209located at a downhole end of the plurality of rotor and stator stages. Alternatively, the plurality of rotor and stator stages may be associated with a single hybrid magnetic thrust bearing located at a downhole end of the plurality of rotor and stator stages and a single hybrid magnetic thrust bearing located at an uphole end of the plurality of rotor and stator stages.

Turning now toFIG. 2B, a seal unit240is described. In an embodiment, the seal unit240comprises a pump coupling242, a motor coupling244, a drive shaft246, a radial bearing241, a first chamber243, a second chamber245, and a housing248. The pump coupling242mechanically couples the drive shaft246to a drive shaft of the centrifugal pump116, and the motor coupling244mechanically couples the drive shaft246to the electric motor110. In an embodiment, the seal unit240may be the seal unit112ofFIG. 1. In an embodiment, the seal unit240comprises a hybrid magnetic thrust bearing209comprising a thrust transfer plate210and a thrust support plate212. The thrust support plate212is retained by the housing248and held stationary. The thrust transfer plate210is coupled to and hence rotates with the drive shaft246. Down thrust on the drive shaft246, transferred from the drive shaft of the centrifugal pump116, may be supported at least in part by the hybrid magnetic thrust bearing209, transferring downwards directed thrust from the drive shaft246to the housing248via the thrust support plate212. In an embodiment, the seal unit240may have more than one hybrid magnetic thrust bearing209. In an embodiment, the seal unit240may have a hybrid magnetic thrust bearing209that is located within the seal unit240so as to support upthrust forces. In this case, the upthrust hybrid magnetic thrust bearing209would be flipped, with the thrust transfer plate210located downhole relative to the thrust support plate212.

Turning now toFIG. 3, is a cross-sectional view of a multi-stage centrifugal pump300showing a plurality of hybrid magnetic thrust bearings: a first hybrid magnetic thrust bearing309a, a second hybrid magnetic thrust bearing309b, and a third hybrid magnetic thrust bearing309c. In an embodiment, the multi-stage centrifugal pump300may comprise any number of hybrid magnetic thrust bearings309. The pump comprises a plurality of impellers302, a plurality of diffusers304, and a drive shaft306. The impellers302are coupled to the drive shaft306and turn with the drive shaft306. The drive shaft306may be turned by the electric motor110. The impellers302provide uplift to fluid301in the pump300. A downwards directed axial thrust associated with the drive shaft306and/or the impeller302may be transferred to the first hybrid magnetic thrust bearing309aand to the second hybrid magnetic thrust bearing309b. The first and second hybrid magnetic thrust bearings309a,309bmay be configured to transfer downwards directed axial thrust from the drive shaft306and/or the impeller302to the diffuser304. An upwards directed axial thrust associated with the drive shaft306and/or the impeller302may be transferred to the third hybrid magnetic thrust bearing309c. The third hybrid magnetic thrust bearing309cmay be configured to transfer upwards directed axial thrust from the drive shaft306and/or the impeller302to the diffuser304. The centrifugal pump300may generate axial thrust directed downhole in a first operating regime and generate axial thrust directed uphole in a second operating regime.

Turning now toFIG. 4A, details of the thrust transfer plate210are described. In an embodiment, the thrust transfer plate210comprises a thrust transfer plate magnetic element402, a bearing surface404, and a support plate406having a shoulder407. The thrust transfer plate210defines a through-hole405to accommodate the drive shaft206,306. The shoulder407may be used to secure the thrust transfer plate210to the drift shaft206,246and to stabilize the thrust transfer plate210. The magnetic element402produces a magnetic field440.

Turning now toFIG. 4B, a cross-section of the magnetic element402is described. In an embodiment, the magnetic element402comprises a plurality of permanent magnets408. The permanent magnets408may be press fit into slots in the magnetic element402. The permanent magnets408may be secured with attachment hardware such as screws, brackets, retaining rings, or other attachment hardware. The permanent magnets408may be secured with glue, epoxy, or another adhesive. The permanent magnets408are each positioned with their magnetic fields oriented in the same direction, for example with their north magnetic poles directed towards the bearing surface404or with their south magnetic poles directed towards the bearing surface404.

Turning now toFIG. 4C, details of the thrust support plate212are described. In an embodiment, the thrust support plate212comprises a thrust support plate magnetic element422, a bearing surface424, and a support plate426. The thrust support plate212defines a through-hole425to accommodate the drive shaft206,246. The magnetic element422produces a magnetic field442.

Turning now toFIG. 4D, a cross-section of the magnetic element422is described. In an embodiment, the magnetic element422comprises a plurality of permanent magnets428. The permanent magnets428may be press fit into slots in the magnetic element422. The permanent magnets428may be secured with attachment hardware such as screws, brackets, retaining rings, or other attachment hardware. The permanent magnets428may be secured with glue, epoxy, or another adhesive. The permanent magnets428are each positioned with their magnetic fields oriented in the same direction, for example with their north magnetic poles directed toward the bearing surface424or with their south magnetic poles directed toward the bearing surface424. If the north magnetic fields of the permanent magnets408are directed toward the bearing surface404, the north magnetic fields of the permanent magnets428are directed toward the bearing surface424. If the south magnetic fields of the permanent magnets408are directed toward the bearing surface404, the south magnetic fields of the permanent magnets428are directed toward the bearing surface424. In this way, the fields of the permanent magnets408are directed contrary to the fields of the permanent magnets428.

Turning now toFIG. 4E, the relationship between magnetic fields440produced by the thrust transfer plate210and magnetic fields442produced by the thrust support plate212is discussed. The magnetic fields440,442are directed to oppose each other and to thereby produce a force of opposition between the magnetic elements402,422. This force is inversely related to the distance between the magnetic elements402,422. As a separation between the thrust transfer plate210and the thrust support plate212is decreased, the opposing force developed between the magnetic elements402,422increases, and as the separation between the thrust transfer plate210and the thrust support plate212is increased, the opposing force developed between the magnetic elements402,422decreases.

Turning now toFIG. 4F, details of a thrust transfer plate450are described. In an embodiment, the thrust transfer plate450comprises a thrust transfer plate magnetic element462, a bearing surface464, and a support plate466. The thrust transfer plate450defines a through-hole465to accommodate structure of the impeller302and/or diffuser304of the centrifugal pump300. The magnetic element462produces a magnetic field468.

Turning now toFIG. 4G, a cross-section of the magnetic element462is described. In an embodiment, the magnetic element462comprises a plurality of permanent magnets469. The permanent magnets469may be press fit into slots in the magnetic element462. The permanent magnets469may be secured with attachment hardware such as screws, brackets, retaining rings, or other attachment hardware. The permanent magnets469may be secured with glue, epoxy, or another adhesive. The permanent magnets469are each positioned with their magnetic fields oriented in the same direction, for example with their north magnetic poles directed towards the bearing surface464or with their south magnetic poles directed towards the bearing surface464.

Turning now toFIG. 4H, details of a thrust support plate452are described. The hybrid magnetic thrust bearing309may comprise the thrust transfer plate450and the thrust support plate452. In an embodiment, the thrust support plate452comprises a thrust support plate magnetic element472, a bearing surface474, and a support plate476. The thrust support plate452defines a through-hole475to accommodate structure of the impeller302and/or of the diffuser304. The magnetic element472produces a magnetic field478.

Turning now toFIG. 4I, a cross-section of the magnetic element472is described. In an embodiment, the magnetic element472comprises a plurality of permanent magnets479. The permanent magnets479may be press fit into slots in the magnetic element472. The permanent magnets479may be secured with attachment hardware such as screws, brackets, retaining rings, or other attachment hardware. The permanent magnets479may be secured with glue, epoxy, or another adhesive. The permanent magnets479are each positioned with their magnetic fields oriented in the same direction, for example with their north magnetic poles directed toward the bearing surface474or with their south magnetic poles directed toward the bearing surface474. If the north magnetic fields of the permanent magnets469are directed toward the bearing surface464, the north magnetic fields of the permanent magnets479are directed toward the bearing surface474. If the south magnetic fields of the permanent magnets469are directed toward the bearing surface464, the south magnetic fields of the permanent magnets479are directed toward the bearing surface474. In this way, the fields of the permanent magnets4469are directed contrary to the fields of the permanent magnets479.

Turning now toFIG. 4J, the relationship between magnetic fields468produced by the thrust transfer plate450and magnetic fields478produced by the thrust support plate452is discussed. The magnetic fields468,478are directed to oppose each other and to thereby produce a force of opposition between the magnetic elements462,472. This force is inversely related to the distance between the magnetic elements462,472. As a separation between the thrust transfer plate450and the thrust support plate452is decreased, the opposing force developed between the magnetic elements462,472increases, and as the separation between the thrust transfer plate450and the thrust support plate452is increased, the opposing force developed between the magnetic elements462,472decreases.

With reference now toFIG. 4A,FIG. 4B,FIG. 4C,FIG. 4D,FIG. 4E,FIG. 4F,FIG. 4G,FIG. 4H,FIG. 4I, andFIG. 4J, in an embodiment the permanent magnets408,428,469,479are rare earth permanent magnets. In an embodiment, the permanent magnets408,428.469.479are samarium-cobalt rare earth permanent magnets. In an embodiment, the permanent magnets408,428,469,479are neodymium rare earth permanent magnets. Samarium-cobalt rare earth magnets may retain desirable magnetic properties better than neodymium rare earth magnets in a high temperature downhole environment. Neodymium rare earth magnets may provide higher magnetic force than samarium-cobalt rare earth magnets when they are used in a moderate temperature downhole environment. The permanent magnets408,428,469,479produce a substantially constant magnetic field strength and may be referred to as passive magnets in contrast to other magnetic devices (e.g., an electro magnet) that may produce a controllable magnetic field strength or where the position of the magnets may be controlled by a feedback control loop (e.g., active control system). For this reason, in some contexts, the hybrid magnetic thrust bearings taught herein may be referred to as passive hybrid magnetic thrust bearings.

The hybrid magnetic thrust bearing209(or309) supports axial thrust with fluid film mechanical force operating between the bearing surfaces404,424(or464,474) augmented by magnetic forces operating between the opposing magnetic fields440,442(or468,478). The contribution of the magnetic forces may permit some of the tolerances of the bearing surfaces404,424(or464,474) to be relaxed, whereby manufacturing costs may be reduced. Additionally, the contribution of the magnetic forces to the fluid film mechanical forces in the hybrid magnetic thrust bearing209(or309) may promote maintaining a greater separation between the bearing surfaces404,424(or464,474) which can reduce bearing surface wear in the presence of abrasive particles.

The hybrid magnetic thrust bearing209,309can be installed with a first orientation (in the orientation illustrated inFIG. 4E,FIG. 4Jin the ESP assembly106to support thrust force directed axially downwards, for example thrust force transferred by the drive shaft206,246,306directed axially downwards. When the hybrid magnetic thrust bearing209,309is installed in the ESP assembly106(in the electric motor110, in the seal unit112, in the centrifugal pump116) in the first orientation, the hybrid magnetic thrust bearing209,309may be said to exert magnetic force on a rotating component (e.g., the drive shaft206,246,306, the rotor202, or the impeller302) directed axially upwards parallel to the central axis of the rotating component and to exert fluid film mechanical force on the rotating component directed axially upwards parallel to the central axis of the rotating component (e.g., the magnetic force augments the fluid film mechanical force). The rotating component can be said to be axially supported by magnetic force applied by the magnetic elements402,422,462,472(e.g., magnetic force developed by the opposing magnetic fields440,442,468,478repelling each other) and by fluid film force applied by the thrust transfer plate210,450and by the thrust support plate212,452of the hybrid magnetic thrust bearing209,309disposed in the first orientation.

The hybrid magnetic thrust bearing209,309can be installed with a second orientation (the orientation ofFIG. 4EorFIG. 4Jrotated 180 degrees—e.g., ‘flipped’) in the ESP assembly106to support thrust force directed axially upwards, for example thrust force transferred by the drive shaft206,246,306directed axially upwards. When the hybrid magnetic thrust bearing209,309is installed in the ESP assembly106(in the electric motor110, in the seal unit112, in the centrifugal pump116) in the second orientation, the hybrid magnetic thrust bearing209,309may be said to exert magnetic force on a rotating component (e.g., the drive shaft206,246,306, the rotor202, or the impeller302) directed axially downwards parallel to the central axis of the rotating component and to exert fluid film mechanical force on the rotating component directed axially downwards parallel to the central axis of the rotating component (e.g., the magnetic force augments the fluid film mechanical force). The rotating component can be said to be axially supported by magnetic force applied by the magnetic elements402,422,462,472(e.g., magnetic force developed by the opposing magnetic fields440,442,468,478repelling each other) and by fluid film force applied by the thrust transfer plate210,450and by the thrust support plate212,452of the hybrid magnetic thrust bearing209,309disposed in the second orientation.

In an embodiment, a separation between the bearing surfaces404,424,464,474is about 3 mils to 10 mils. In another embodiment, however, the separation between the bearing surfaces404,424,464,474may have a value outside the range of 3 mils to 10 mils. In an embodiment, the separation between the bearing surfaces404,424,464,474is greater than the separation maintained in conventional thrust bearings. The surface roughness of the bearing surfaces404,424,464,474may be about 20 millionths of an inch of surface variation, while conventional thrust bearings may have a surface roughness of about 10 millionths of an inch in surface variation. In an embodiment, the surface finish of the bearing surfaces404,424,464,474have a roughness of between 8 micro inches and 22 micro inches.

Turning now toFIG. 5AandFIG. 5B, further details of the hybrid magnetic thrust bearing209are described. It is noted that the same observations here made with reference to the hybrid magnetic thrust bearing209apply also to the hybrid magnetic thrust bearing309. In an embodiment, the magnetic operation of the hybrid magnetic thrust bearing209may contribute to stabilizing the bearing209and deterring or mitigating a wobble that may occur. InFIG. 5A, the hybrid magnetic bearing209is illustrated as having raised a left side of the thrust transfer plate210relative to the thrust support plate212, and having lowered a right side of the thrust transfer plate210relative to the thrust support plate212. Because the right sides of the plates210,212are closer together, the magnetic force502applied to the thrust transfer plate210at the right side is increased, and because the left sides of the plates210,212are further apart, the magnetic force504applied to the thrust transfer plate210at the left side is reduced. InFIG. 5B, the hybrid magnetic bearing209is illustrated as having raised a right side of the thrust transfer plate210relative to the thrust support plate212, and having lowered a left side of the thrust transfer plate210relative to the thrust support plate212. Because the left sides of the plates210,212are closer together, the magnetic force512applied to the thrust transfer plate210at the left side is increased, and because the right side of the plates210,212are further apart, the magnetic force514applied to the thrust transfer plate210at the right side is reduced. These imbalanced forces tend to urge the plates210,212to return to a steady state, level orientation. It is understood that the tilting of the plates210,212relative to each other depicted inFIG. 5AandFIG. 5Bis greatly exaggerated to illustrate this stabilizing feature.

In traditional thrust bearings that operate solely using fluid film mechanical forces, wear of bearing surfaces can result in oscillatory vibration that may establish an eccentric gap between the bearing surfaces. This eccentric gap promotes yet more wear of the bearing surface. The eccentric gap increases the infiltration of particles into the gap which disrupts operation of the thrust supporting fluid film mechanical forces and further accelerates wear of the bearing surfaces. The thrust supporting force of the magnetic field interactions of the hybrid magnetic thrust bearings209,309taught herein, by contrast, act so as to offset and compensate against uneven wear. As uneven wear occurs on a bearing surface, the bearing surfaces at the point of wear tend to bring the magnetic elements closer together, increasing the opposing magnetic forces, thereby offsetting the lost fluid film mechanical force at the point of wear. This can promote more even wear and avoidance of the oscillatory vibration mentioned above, thereby reducing the rate of wear of the bearing surfaces. The hybrid magnetic thrust bearings209,309taught herein may counteract oscillatory vibrations that sometimes develop in conventional thrust bearings as a result of eccentric wear and may in part correct any eccentric wear which may develop in the hybrid magnetic thrust bearings209,309.

Turning now toFIG. 6, a method600is described. In an embodiment, method600is a method of operating in an electric submersible pump (ESP) assembly. At block602, the method600comprises providing electric power to an ESP assembly disposed in a wellbore. At block604, the method600comprises exerting magnetic force on a rotating component of the ESP assembly directed axially upwards parallel to a central axis of the rotating component. In an embodiment, the method600comprises exerting fluid film force on the rotating component directed axially upwards parallel to the central axis of the rotating component. In an embodiment, the method600comprises exerting magnetic force on the rotating component directed axially downwards parallel to the central axis of the rotating component.

Turning now toFIG. 7, a method700is described. In an embodiment, the method700is a method of lifting fluid in a wellbore. At block702, the method700comprises providing electric power to an electric motor of an electric submersible pump (ESP) assembly, wherein the electric motor is supported axially at least in part by at least one hybrid magnetic thrust bearing disposed inside the electric motor. In an embodiment, the electric motor is axially supported by magnetic force applied by a magnetic element of the at least one hybrid magnetic thrust bearing disposed inside the electric motor and by fluid film force applied by a thrust transfer plate and a thrust support plate of the at least one hybrid magnetic thrust bearing disposed inside the electric motor interacting with a fluid provided inside the electric motor. In an embodiment, the electric motor comprises a plurality of rotor and stator stages.

At block704, the method700comprises providing mechanical torque by the electric motor to a centrifugal pump of the ESP assembly, wherein a drive shaft of the centrifugal pump is supported axially at least in part by at least one hybrid magnetic thrust bearing disposed inside the centrifugal pump. In an embodiment, the centrifugal pump comprises a plurality of pump stages. In an embodiment, the drive shaft of the centrifugal pump is axially supported by magnetic force applied by a magnetic element of the at least one hybrid magnetic thrust bearing disposed inside the centrifugal pump and by fluid film force applied by a thrust transfer plate and a thrust support plate of the at least one hybrid magnetic thrust bearing disposed inside the centrifugal pump interacting with the fluid. The magnetic element comprises a plurality of permanent magnets, for example a plurality of rare earth permanent magnets or other kind of permanent magnets. In an embodiment, a drive shaft of a seal unit of the ESP assembly is axially supported at least in part by at least one hybrid magnetic thrust bearing disposed inside the seal unit, wherein the drive shaft of the seal unit provides the mechanical torque from the electric motor to the drive shaft of the centrifugal pump.

At block706, the method700comprises lifting a fluid in a wellbore by the centrifugal pump. The fluid may comprise one or more hydrocarbons. The fluid may comprise water. The fluid may comprise a mixture of oil and gas. The fluid may comprise a mixture of hydrocarbons and water. The fluid may comprise a mixture of oil, gas, and water.

ADDITIONAL DISCLOSURE

A first embodiment, which is an electric submersible pump (ESP) assembly, comprising an electric motor, a centrifugal pump, and a hybrid magnetic thrust bearing, wherein the hybrid magnetic thrust bearing is disposed inside the electric motor or disposed inside the centrifugal pump.

A second embodiment, which is the ESP assembly of the first embodiment, wherein the hybrid magnetic thrust bearing comprises a thrust transfer plate that is coupled to a drive shaft of the ESP assembly and a thrust support plate that is coupled to a housing of the ESP assembly, the thrust transfer plate comprises a thrust transfer plate magnetic element, the thrust support plate comprises a thrust support plate magnetic element, and a magnetic field of the thrust transfer plate magnetic element is directed opposite to a magnetic field of the thrust support plate magnetic element.

A third embodiment, which is the ESP assembly of the second embodiment, wherein the thrust transfer plate magnetic element comprises a plurality of permanent magnets and the thrust support plate magnetic element comprises a plurality of permanent magnets.

A fourth embodiment, which is the ESP assembly of the third embodiment, wherein the permanent magnets of both the thrust transfer plate magnetic element and the thrust support plate magnetic element are rare earth permanent magnets.

A fifth embodiment, which is the ESP assembly of the fourth embodiment, wherein the rare earth permanent magnets comprise samarium-cobalt rare earth permanent magnets or neodymium rare earth permanent magnets.

A sixth embodiment, which is the ESP assembly of any of the first, the second, the third, the fourth, or the fifth embodiment, further comprising a seal unit located between the electric motor and the centrifugal pump, wherein the seal unit comprises at least one hybrid magnetic thrust bearing.

A seventh embodiment, which is the ESP assembly of the sixth embodiment, wherein the seal unit comprises at least one hybrid magnetic thrust bearing disposed to support downward thrust of a drive shaft of the seal unit and at least one hybrid magnetic thrust bearing disposed to support upward thrust of the drive shaft of the seal unit.

An eighth embodiment, which is the ESP assembly of any of the first, the second, the third, the fourth, the fifth, the sixth, or the seventh embodiment, wherein the hybrid magnetic thrust bearing is disposed in the electric motor.

A ninth embodiment, which is the ESP assembly of any of the first, the second, the third, the fourth, the fifth, the sixth, the seventh, or the eighth embodiment, wherein the hybrid magnetic thrust bearing is disposed in the centrifugal pump.

A tenth embodiment, which is a method of operating an electric submersible pump (ESP) assembly, comprising providing electric power to an ESP assembly disposed in a wellbore and exerting magnetic force on a rotating component of the ESP assembly directed axially upwards parallel to a central axis of the rotating component.

An eleventh embodiment, which is the method of the tenth embodiment, comprising exerting fluid film force on the rotating component directed axially upwards parallel to the central axis of the rotating component.

A twelfth embodiment, which is the method of the eleventh embodiment, comprising exerting magnetic force on the rotating component directed axially downwards parallel to the central axis of the rotating component.

A thirteenth embodiment, which is the method of lifting fluid in a wellbore, comprising providing electric power to an electric motor of an electric submersible pump (ESP) assembly, wherein the electric motor is supported axially at least in part by at least one hybrid magnetic thrust bearing disposed inside the electric motor, providing mechanical torque by the electric motor to a centrifugal pump of the ESP assembly, wherein a drive shaft of the centrifugal pump is supported axially at least in part by at least one hybrid magnetic thrust bearing disposed inside the centrifugal pump, and lifting a fluid in a wellbore by the centrifugal pump.

A fourteenth embodiment, which is the method of the thirteenth embodiment, wherein the fluid lifted in the wellbore is a hydrocarbon or water.

A fifteenth embodiment, which is the method of the thirteenth or the fourteenth embodiment, wherein the drive shaft of the centrifugal pump is axially supported by magnetic force applied by a magnetic element of the at least one hybrid magnetic thrust bearing disposed inside the centrifugal pump and by fluid film force applied by a thrust transfer plate and a thrust support plate of the at least one hybrid magnetic thrust bearing disposed inside the centrifugal pump interacting with the fluid.

A sixteenth embodiment, which is the method of the fifteenth embodiment, wherein the magnetic element comprises a plurality of permanent magnets.

A seventeenth embodiment, which is the method of any of the thirteenth, the fourteenth, the fifteenth, or the sixteenth embodiment, wherein a drive shaft of a seal unit of the ESP assembly is axially supported at least in part by at least one hybrid magnetic thrust bearing disposed inside the seal unit, wherein the drive shaft of the seal unit provides the mechanical torque from the electric motor to the drive shaft of the centrifugal pump.

An eighteenth embodiment, which is the method of any of the thirteenth, the fourteenth, the fifteenth, the sixteenth, or the seventeenth embodiment, wherein the electric motor is axially supported by magnetic force applied by a magnetic element of the at least one hybrid magnetic thrust bearing disposed inside the electric motor and by fluid film force applied by a thrust transfer plate and a thrust support plate of the at least one hybrid magnetic thrust bearing disposed inside the electric motor interacting with a fluid provided inside the electric motor.

A nineteenth embodiment, which is the method of any of the thirteenth, the fourteenth, the fifteenth, the sixteenth, the seventeenth, or the eighteenth embodiment, wherein the electric motor comprises a plurality of rotor and stator stages.

A twentieth embodiment, which is the method of any of the thirteenth, the fourteenth, the fifteenth, the sixteenth, the seventeenth, the eighteenth, or the nineteenth embodiment, wherein the centrifugal pump comprises a plurality of pump stages.