WO2025264690A1

WO2025264690A1 - System and method having an induction motor artificial lift pump

Info

Publication number: WO2025264690A1
Application number: PCT/US2025/033999
Authority: WO
Inventors: Raju Ekambaram; Stanislav Konstantinovich IVANOV; Vignesh AMUTHA NILAVAZHAGAN; Pradeep MAHADEVAN; You Cheng JEE; Sethuraj ARUMUGAM; Preethi KODURU; Chee Shuan CHAN
Original assignee: Schlumberger Canada Ltd; Services Petroliers Schlumberger SA; Schlumberger Technology BV; Schlumberger Technology Corp
Current assignee: Schlumberger Canada Ltd; Services Petroliers Schlumberger SA; Schlumberger Technology BV; Schlumberger Technology Corp
Priority date: 2024-06-18
Filing date: 2025-06-17
Publication date: 2025-12-26
Anticipated expiration: 2026-12-18

Abstract

A system includes an induction motor configured to drive an electric submersible pump (ESP). The induction motor includes a one or more rotors disposed about a rotational axis, and a plurality of bearings disposed about the rotational axis. Each bearing of the plurality of bearings is disposed axially between a pair of rotors of the one or more rotors. The induction motor further includes one or more stators disposed about the one or more rotors.

Description

SYSTEM AND METHOD HAVING AN INDUCTION MOTOR ARTIFICIAL

LIFT PUMP

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to and benefit of Singapore Provisional Patent Application No. 10202401764V, filed June 18, 2024, which is herein incorporated by reference in its entirety for all purposes.

BACKGROUND

[0002] The present disclosure relates generally to an induction motor artificial lift pump.

[0003] This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

[0004] Certain wells may utilize artificial means to increase the flow of liquids (e.g., crude oil or water) to lift the liquids from the reservoir to the surface. The use of artificial means to increase the flow of liquids may be due to insufficient pressure in the reservoir, or a need to increase the liquid flow rate. Various types of equipment and methods are available for such artificial lift purposes, such as electric submersible pumps (ESPs).

[0005] ESPs may operate at a speed of 3500 rpm to generate lift in reservoirs. Unfortunately, the operating speed of existing ESPs may result in a limited lift capacity, a long pump string, a limited setting depth, and a limited ability to handle well deviations. Additionally, the existing ESPs may include permanent magnet motors for reasons of efficiency. Unfortunately, the permanent magnet motors may be costly and difficult to operate. For at least these reasons, a need exists for an induction motor ESP system that is able to achieve high operating speeds BRIEF DESCRIPTION

[0006] Certain embodiments commensurate in scope with the originally claimed invention are summarized below. These embodiments are not intended to limit the scope of the claimed invention, but rather these embodiments are intended only to provide a brief summary of possible forms of the invention. Indeed, the invention may encompass a variety of forms that may be similar to or different from the embodiments set forth below.

[0007] In certain embodiments, a system includes an induction motor configured to drive an electric submersible pump (ESP). The induction motor includes a one or more rotors disposed about a rotational axis, and a plurality of bearings disposed about the rotational axis. Each bearing of the plurality of bearings is disposed axially between a pair of rotors of the one or more rotors. The induction motor further includes one or more stators disposed about the one or more rotors.

[0008] In certain embodiments, a method includes driving an electric submersible pump (ESP) with an induction motor. The induction motor includes a one or more rotors disposed about a rotational axis and a plurality of bearings disposed about the rotational axis, wherein each bearing of the plurality of bearings is disposed axially between a pair of rotors of the one or more rotors. The induction motor further includes one or more stators disposed about the one or more rotors.

[0009] In certain embodiments, a system includes a rotor of a plurality of rotors of an induction motor configured to drive an electric submersible pump (ESP). The rotor includes a lamination, a plurality of copper bars disposed in the lamination, and first and second copper end rings coupled to the plurality of copper bars at axially opposite ends of the rotor. The rotor has an axial length that is less than or equal to 12 inches.

DRAWINGS

[0010] These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: [0011] FIG. 1 is a side view of an embodiment of an ESP system having a pump section, a protector section, and a motor section, in accordance with the present disclosure;

[0012] FIG. 2 is a perspective cutaway view of an embodiment of an induction motor of the motor section of the ESP system of FIG. 1, in accordance with the present disclosure;

[0013] FIG. 3 is a side view of an embodiment of a rotor of the induction motor of the ESP system of FIGS. 1 and 2, illustrating the length and diameter of the rotor, in accordance with the present disclosure;

[0014] FIG. 4 is a side view of an embodiment of a shaft of the induction motor of the ESP system of FIGS. 1 and 2, illustrating keyways disposed along a length of the shaft, in accordance with the present disclosure;

[0015] FIG. 5 is a schematic cross-sectional view of an embodiment of the induction motor of the ESP system of FIG. 4, further illustrating the key ways, in accordance with the present disclosure;

[0016] FIG. 6 is a schematic cross-sectional view of the induction motor of the ESP system of FIGS. 1-5, further illustrating internal components of the ESP system, in accordance with the present disclosure; and

[0017] FIG. 7 is a schematic cross-sectional view of a head of the induction motor of FIG. 6, further illustrating bearings and a lubrication system.

DETAILED DESCRIPTION

[0018] One or more specific embodiments of the present disclosure will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers’ specific goals, such as compliance with system- related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

[0019] When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Any examples of operating parameters and/or environmental conditions are not exclusive of other parameters/conditions of the disclosed embodiments.

[0020] Illustrative examples of the subject matter claimed below will now be disclosed. In the interest of clarity, not all features of an actual implementation are described in this specification. It will be appreciated that in the development of any such actual implementation, numerous implementation-specific decisions may be made to achieve the developers’ specific goals, such as compliance with system -related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort, even if complex and time-consuming, would be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

[0021] Embodiments of the present disclosure are directed towards an induction motor for electronic or electric submersible pump (ESP) systems, with the capability of achieving high operating speeds. The ESP system with the induction motor is configured to operate at speeds up to 12,000 rpm or more, thereby generating higher lift capabilities. Specifically, the operation speed may be greater than or equal to 4,000 rpm. For example, the operation speed may be greater than or equal to 5,000 rpm, greater than or equal to 6,000 rpm, greater than or equal to 7,000 rpm, greater than or equal to 8,000 rpm, greater than or equal to 9,000 rpm greater than or equal to 10,000 rpm, or greater than or equal to 11,000 rpm. Additionally, the ESP system with the induction motor may provide reduced costs, a shorter pump string, a greater setting depth, and the ability to handle greater well deviations. The ESP system with the induction motor also may enable improved operations and controllability, thereby improving the efficiency and performance of the ESP system. As discussed in further detail below, the ESP system may include various improvements to enable high operating speeds, including shorter and/or smaller diameter rotors, more closely spaced bearings, and tighter tolerance between the rotors and surrounding stators. For example, a length-to-diameter ratio of the rotors may be adjusted to provide a desired spacing of the bearings to reduce vibration at the high operating speeds. The ESP system also may include high temperature materials used for the magnet wires. The ESP system also may include one or more mass balance adjustments of the rotors (e.g., dual keyways), such that the mass is uniform circumferentially around and axially along the rotors to reduce vibration at the high operating speed.

[0022] Turning now to the figures, FIG. 1 is a side view of an embodiment of an ESP system 10 having various enhancements to enable high operating speeds. The ESP system 10 may include at least a pump section 12, a protector section 14, a motor section 16, and a power cable 18 connected to the motor section 16. However, in some embodiments, the ESP system 10 may also include a multiphase gas handling system (MGHS), a vortex gas separator assembly (VGSA), or a combination thereof. An MGHS may be beneficial in assisting pumps to operate with multiphase fluid flows having a high gas-volume fraction (GVF) up to 75% free gas. For example, the MGHS may include helicoaxial, multiphase stages. Further, the VGSA may efficiently separate gas from liquid in the multiphase fluid flow. In embodiments in which the ESP system 10 includes an MGHS, or a VGSA and an MGHS, the VGSA and MGHS may be located between the pump section 12 and the protector section 14. While the illustrated ESP system 10 may be greater than 30 feet long, an ESP system 10 with a MGHS or an MGHS and VGSA may be anywhere from 3 to 12 feet longer, based on the size of the MGHS and VGSA.

[0023] The pump section 12 may include a centrifugal pump configured to rotate to pump fluid through the ESP system 10. The centrifugal pump may be made up of a rotating impeller and stationary diffuser. Further, the centrifugal pump may have stages stacked incrementally until the ESP system 10 reaches a desired pressure and flow rate. In each stage of the pump section 12, the production fluid may travel through a rotating impeller and diffuser.

[0024] The protector section 14 may serve multiple protection purposes. One benefit of the protector section 14 is that the motor section 16 contains oil, which expands as the motor heats up at high speeds. As such, the protector section 14 may accommodate the expanded oil volume and contracted oil volume. Further, the protector section 14 may protect the motor section 16 from the downward force generated by the pump section 12. Additionally, the protector section 14 may act as a seal to protect the producing fluid moving in the ESP system 10 from the oil in the motor section 16.

[0025] The motor section 16 may provide power to the pump section 12 of the ESP system 10. In the present disclosure, the motor section 16 may be configured to handle high rates of shaft spinning speed. The configuration of the motor section 16 that provides adequate support for a high operating speed (e.g., up to 12,000 rpm) is described in more detail in FIG. 2-5. In certain embodiments, the motor section 16 includes an induction motor 20, shorter and/or smaller diameter rotors, more closely spaced bearings, and tighter tolerance between the rotors and surrounding stators. The ESP system also may include one or more mass balance adjustments of the rotors (e.g., dual keyways) to reduce vibration at the high operating speed.

[0026] The power cable 18 delivers power to the motor section 16 from the surface of the borehole. The power cable 18 may be banded or strapped to production tubing in intervals from below the wellhead to the motor section 16 to minimize mechanical wear on the power cable 18. Further, the power cable 18 may be connected to the motor section 16 via a 3-phase connector (e.g., quick-plug motor connector) as described more in FIG. 2.

[0027] FIG. 2 is a perspective cutaway view of an embodiment of the induction motor 20 of the motor section 16 of the ESP system 10 of FIG. 1. The illustrated embodiment shows an electromagnetic 2-pole configuration of the induction motor 20. The induction motor 20 may include a housing 50 (e.g., annular housing) for a one or more rotors 52 (e.g., annular rotor) arranged in series about an extended shaft 54 (e.g., cylindrical shaft), wherein each rotor 52 has a corresponding stator 56 (e.g., annular stator). In some embodiments, the stator 56 extends about multiple or all of the rotors 52. For example, the induction motor 20 may include a single stator 56 (e.g., one stack of laminated stators) supporting all of the rotors 52. The induction motor 20 may include a plurality of the rotors 52 (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or more) arranged within the stator(s) 56 to define a plurality of induction motor sections 22. As discussed in further detail below, the induction motor sections 22 include bearings 70 on opposite axial ends of each rotor 52, wherein the rotors 52 are sized to position the bearings 70 at a relatively short axial spacing to enable a high rotational speed of the induction motor 20. Further, the housing 50 may include a gauge housing portion 68, which houses one or more sensors configured to monitor the motor speed, motor temperature, motor fluid temperature and pressure, motor vibration, and other parameters relevant to the operation of the induction motor 20. The sensors provide sensor feedback (e.g., motor speed, motor temperature, motor fluid temperature and pressure, motor vibrations, and other parameters) to a controller 72 coupled to the induction motor 20. The controller 72 includes a processor 74, memory 76, and instructions stored on the memory 76 and executable by the processor 74 to control operation of the induction motor 20 in response to the sensor feedback. For example, if the induction motor 20 has a pressure, temperature, or vibration level above a threshold, then the controller 72 may reduce a rotational speed to protect the motor section 16, particularly when operating the induction motor 20 at a high rotational speed.

[0028] Each rotor 52 in the one or more rotors 52 may be designed with various high speed improvements, thereby enabling a reliable high speed operation of the induction motor 20 and the entire ESP system 10 for continuous long-term operation. For example, the high speed improvements may include features to reduce friction via the bearings 70, improve balancing and reduce vibration of the rotors 52, and increase structural integrity to endure the high speed operation. As such, in one or more embodiments, each rotor 52 may include a rotor lamination 57, rotor copper cage 58, and rotor snap rings 60. For example, each rotor 52 may include the rotor copper cage 58 having a plurality of rotor copper bars (e.g., axial copper bars) coupled to axially opposite copper end rings 59, wherein the rotor copper cage 58 is embedded or supported by the rotor lamination 57. The rotor lamination 57 may be a cylindrical core of steel laminations, and the rotor copper bars may be formed (e.g., cast) within axial slots in the rotor lamination 57. The rotor lamination 57 may be magnetized and demagnetized to assist the induction motor 20 with rotating the rotors 52 around the shaft 54. Further, each rotor 52 may be sandwiched between the copper end rings 59 on each axial end of each rotor 52. The rotor copper cage 58 may assist the induction motor 20 with the creation of the magnetic field used to operate the ESP system 10. Each rotor 52 may have one or more snap rings 60 used to attach the rotor copper cage 58 or other rotor components to the rotor 52, which may be beneficial at high rotational speeds. Further, the snap rings 60 may secure the rotor 52 in place in the induction motor 20 and separate the rotors 52, so the rotors 52 do not stack on top of each other at the high rotational speed. The rotors 52 also may be dynamically balanced to maintain equilibrium as the rotors 52 rotate at the high rotational speed. As such, the rotors 52 may be short (e.g., less than 12 inches long), but there may be more rotors 52 to counteract the small size of the rotors 52.

[0029] One or more stators 56 surround the rotors 52. In some embodiments, the induction motor 20 may include one stator 56 for each rotor 52. In other embodiments, the induction motor 20 includes one stator 56 shared by all of the rotors 52. Each stator 56 may include a stator lamination 62 and a stator copper wire 66 (e.g., a stator winding). In operation, the controller 72 is configured to control a supply of AC power to the stator copper wire 66 to provide a rotating magnetic field, which induces an electrical current in the rotors 52 to create magnetic fields that react against the rotating magnetic field from the stator 56. These opposing magnetic fields result in rotation of the rotors 52. Thus, the induction motor 20 creates torque solely by induction.

[0030] In the illustrated embodiment, the induction motor 20 includes the bearings 70 at axially opposite ends of each rotor 52, such that the bearings 70 are between each pair of adjacent rotor 52 and at the axially opposite ends of the series of rotors 52. The bearings 70 may include a rolling element bearing, a fluid bearing, a self-lubricating bearing, a magnetic bearing, a composite bearing, or a combination thereof. The rolling element bearing may include a plurality of rolling elements (e.g., balls, cylindrical rollers, tapered rollers, etc.) between inner and outer annular raceways. The fluid bearing provides a layer of fluid between inner and outer annular bodies. The selflubricating bearing includes a lubricant material embedded or impregnated into sliding annular surfaces (e.g., bearing surfaces) of inner and outer annular bodies. The lubricant material may include a liquid and/or a solid lubricant, such as oil, graphite, lead, molybdenum disulfide (MoS2), polymer, or any combination thereof. For example, the self-lubricating bearing may include an oil impregnated metal bearing or a metal-polymer low friction bearing, wherein the metal may include sintered bronze, copper, aluminum alloy, lead, or sintered iron and copper. The polymer of the metal- polymer low friction bearing may include Polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), Nylon, Polyoxymethylene (POM), polyester, ultra-high molecular weight polyethylene (UHMWPE), or any combination thereof. For example, an embodiment of the metal-polymer low friction bearing includes a sintered bronze impregnated and/or covered with PTFE for the inner and/or outer annular bodies of the bearing 70.

[0031] In certain embodiments, the bearings 70 may include a cylindrical bearing, a tri-low bearing, offset bearings, bearing with axial grooves, a modified tri-low to trilobe bearing, or a combination thereof. In other embodiments, bearings 70 may include a DB4 bearing with a carbon steel (CS) sleeve. Further, in some embodiments, each bearing 70 may have a low friction sleeve. Each bearing 70 has a stationary portion and a mobile portion. There may be smaller running clearances (e.g. tolerances, space between) between the stationary portion of the bearing 70 and the mobile portion of the bearing 70. The limited clearances on the bearings 70 may minimize vibrations of the rotor 52 or induction motor 20 during high speed operations. The minimization of vibrations at high speed operations may limit wear on the induction motor 20 and its parts, while also increasing the energy efficiency of the motor section 16, as less energy will go into the vibrations or counteracting the vibrations.

[0032] Further, the induction motor 20 may include the controller 72 coupled to the various sensors and the windings of the stator 56. The controller 72 is configured to operation of the ESP system 10, and particularly the pumping parameters (e.g., flow rate, pressure, etc.) of the pump section 12 via control of the induction motor 20 of the motor section 16. For example, the controller 72 is configured to control the torque provided by the induction motor 20 by actuating each of the rotors 52 via the stator 56. In some embodiments, the controller 72 is configured to independently and selectively control operation of the rotors 52 to provide the torque needed to operate the pump section 12 of the ESP system 10. The controller 72 is configured to monitor sensor feedback associated with the motor section 16 and the pump section 12, and adjust the induction motor 20 to vary the pumping parameters of the pump section 12. For example, the controller 72 may be configured to increase a rotational speed of the induction motor 20 if the rotational speed is below a lower threshold or decrease the rotational speed of the induction motor 20 if the rotational speed is above an upper threshold. By further example, the controller 72 may be configured to maintain or increase a rotational speed of the induction motor 20 if a motor temperature, a motor fluid pressure, a motor fluid temperature, a motor vibration, or any combination thereof, is within an acceptable range (e.g.,. between upper and lower thresholds). However, the controller 72 may be configured to decrease a rotational speed of the induction motor 20 if a motor temperature, a motor fluid pressure, a motor fluid temperature, a motor vibration, or any combination thereof, is outside of an acceptable range (e.g.,. temperature, pressure, or vibration above an upper threshold). In certain embodiments, the controller 72 may be configured to monitor sensors feedback of bearing parameters (e.g., temperature, vibration, etc.) of the bearings 70 and rotor parameters of the rotors 52 (e.g., temperature, vibration, etc.) individually and collectively to help identify any undesirable trends or real-time issues in health conditions of the bearings 70 and rotors 52. Accordingly, the controller 72 may be configured to enable real-time detection of health conditions and initial real-time remedial actions to help reduce or eliminate the health conditions, such as automatically reducing the rotational speed, flushing the bearing 70 with a cleaning fluid and/or lubricant, and scheduling a maintenance operation.

[0033] As such, the controller 72 may adjust operation of the motor section 16 based on parameters monitored by the sensors coupled to the gauge housing portion 68, such as temperature, speed, pressure, and the like, to help ensure reliable operation at the high rotational speed while also providing a wide range of rotational speeds. In certain embodiments, the controller 72 may be configured to operate the induction motor 20 of the ESP system 10 at a high rotational speed of at least equal to or greater than 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, or 12000 rpm. In certain embodiments, the controller 72 may be configured to operate the induction motor 20 of the ESP system 10 at a rotational speed range between 1000 and 12000 rpm, thereby providing flexible operation at low, medium, and high rotational speeds.

[0034] On an axial end portion of the motor section 16 towards the protector section 14, which may also be referred to as a head 90 of the motor section 16, the motor section 16 may include a quick-plug motor lead extension (MLE) connector 80 (e.g., quick connector). The quick connector 80 may connect the power cable 18 (e.g., three-phase conductors) to the windings of the stator 56 of the motor section 16. The quick connector 80 may include a MaxLok connector and a Maxjoint ESP flange connection made by SLB of Houston, TX. Further, the axial end portion of the motor section 16 towards the protector section 14 may also include a high/low thrust bearing 82, which provides for smooth rotation of the rotors 52 in the induction motor 20. In certain embodiments, the axial end portion of the motor section 16 also includes bolt holes 84 configured to hold wedge-type block washers, which may minimize disconnection at high speeds.

[0035] The motor section 16 may connect to the protector section 14 via the extended shaft 54. The connecting end of the protector section 14 may include a shaftlip seal 86 to minimize oil leakage. To further minimize oil leakage, the connecting end of the protector section 14 may include an oil communication valve 88. In one or more embodiments, the size of electrical windings and conductors of the induction motor 20 is optimized for maximum efficiency. In one or more embodiments, the induction motor 20 may further include components rated for high-temperature usage.

[0036] FIG. 3 is a side view of an embodiment of a rotor of the induction motor 20 of the ESP system of FIGS. 1 and 2, illustrating a length 100 (L) and a diameter 102 (D) of the rotor configured to help enable a high rotational speed of the induction motor 20. The diameter 102 of each rotor may include an outer diameter. The outer diameter may be less than or equal to 3 inches. The length 100 (L) of each rotor may be less than or equal to 17 inches. In particular, the length 100 (L), the diameter 102 (D), and/or a length-to-diameter ratio (L/D) of the rotor 52 is optimized so that bearing spacing within the rotor is improved to produce lower vibration during high-speed operations. Specifically, the L/D ratio may be between 3.5 and 9, for example, 3.5, 3.6, 3.7, 3.75, 3.80, 3.9, 4, 4.5, 5, 5.50, 6, 6.25, 6.5, 7, 7.5, 8, 8.5, 8.75, 9. In the illustrated embodiment, which focuses on a rotor 52 and the rotor copper cage 58 and bearings 70, which accompany the rotor 52, the length 100 to diameter 102 ratio (L/D) is central to the improvements for high-speed operations. Specifically, smaller diameters 102 of the rotors 52 may minimize vibrations at high rotational speeds. Further, the length 100 of the rotors 52 may be relatively small as compared with conventional rotors 52 of ESP systems, as multiple rotors 52 are utilized in series, rather than having one or more long rotors 52 with a large diameter 102.

[0037] In certain embodiments, the length 100 (L) may be less than or equal to about 12 inches, such that the bearings 70 may be spaced apart from one another by the same length 100 (L). In some embodiments, the length 100 (L) may be less than or equal to about 10, 11, 12, 13, 14, or 15 inches, or in a range of 8 to 16 inches, 9 to 15 inches, 10 to 14 inches, or 11 to 13 inches. Thus, the bearings 70 are more closely spaced together (e.g., close axial spacing) as compared with a rotor having a longer length of 18, 20, 22, or 24 inches. The relatively close axial spacing of the bearings 70 (e.g., length 100) results in greater stability and lower vibration at a high rotational speed. Additionally, the bearings 70 are designed for high speed operation, such that the bearings 70 also reduce friction and vibration during the high speed operation.

[0038] In certain embodiments, the diameter 102 (D) may be less than or equal to about 2.25 inches, such that rotor 52 has a reduced mass as compared with a larger diameter rotor 52. However, the diameter 102 (D) may be less than or equal to about 2, 2.25, 2.5, 2.7, or 3 inches, or in a range of 2.75 to 3.00, 2.50 to 3.00, 2.25 to 3.00, 2.25-2.50, 1.75 to 2.75, 2 to 2.5, or 2.15 to 2.35 inches. In certain embodiments, the combination of the shorter length 100 (L) and the smaller diameter 102 (D) helps to reduce the overall mass of the rotor 52 for improved acceleration, reduced vibration, and improved stability at high-speed operations. Additionally, the rotor 52 may include mass balancing to ensure a uniform distribution of mass along the length 100 and around a circumference of the rotor 52, including grooves and keys for coupling the rotor 52 with the shaft 54, as discussed in further detail below.

[0039] FIG. 4 is a side view of an embodiment of the shaft 54 of the induction motor 20 of the ESP system 10 of FIGS. 1 and 2, illustrating keyways 120 disposed along the length 100 of the shaft 54. In one or more embodiments, the induction motor 20 may include keyways 120 (e.g., axial slots) on opposing sides along the length 100 of the shaft 54. This includes dual keyways 120A, 120B over some portion of the shaft length where there would be no keys assembled during operation. The keyways 120 assist the shaft 54 in remaining mechanically balanced during high-speed operations. The keyways 120 provide a location for keys (e.g., axial bars or keys) to be inserted prior to operation to mechanically balance the motor section 16 during high speed operations. In some embodiments, the keyways 120 may be a similar length along the shaft 54. However, in other embodiments, the key ways 120 may be different lengths based on the existing weight distribution of the shaft 54 and rotors 52 and the intended operation speed of the motor section 16. In the illustrated embodiment, the keyways 120 (e.g., 120A, 120B) are disposed on diametrically opposite sides of the shaft 54. Additionally, the keyways 120 (e.g., 120A, 120B) may include keyway entry portions 121 (121A, 121B) have a greater size (e.g., radial depth) than the keyways 120 (e.g., 120A, 120B) to facilitate insertion or removal of keys into the keyways 120 (e.g., 120 A, 120B). As illustrated, the keyway entry portions 121 (121 A, 121B) may be axially offset from one another to provide different axial positions for insertion of keys. In certain embodiments, the shaft 54 and the rotor 52 are further balanced for high-speed operation by providing a substantially equal mass along the keyways 120 (e.g., 120A, 120B) and/or the keyway entry portions 121 (121 A, 121B) as discussed in further detail below with reference to FIG. 5.

[0040] FIG. 5 is a schematic cross-sectional view of an embodiment of the induction motor 20 of the motor section 16 of the ESP system 10 of FIG. 4, further illustrating the keyways 120 (e.g., 120A, 120B) disposed along a length of the shaft 54 of the motor section 16. The illustrated embodiment is a radial cross-section of the rotor 52 disposed about the shaft 54 to illustrate the different keyways 120A, 120B. As discussed in detail below, the illustrated embodiment provides a substantially equal mass in the shaft 54 and the rotor 52 to counter differences in keys and keyways between the shaft 54 and the rotor 52.

[0041] The keyways 120 may operate differently in the illustrated embodiment. One key way 120 A may align with and extend axially along a corresponding key way 122 A in the rotor 52, thereby defining a full size keyway 124A (e.g., both 120A, 122A) to accept a full size key 126A (e.g., a driving key). The full size key 126A within the full size key ways 124 A enables a mechanical coupling between the shaft 54 and rotor 52, thereby enabling torque transfer between the shaft 54 and the rotor 52. Specifically, the full size key 126 A may fit inside the full size key way 126 A along all or part of the length 100 of the rotor 52, such that there is a mechanical engagement between the shaft 54 and the rotor 52 along the length 100 of the rotor 52. Conversely, the key way 120B may not align with and extend axially along a corresponding keyway in the rotor 52, thereby defining a half size key way 124B (e.g., only the key way 120B) that accepts a half size key 126B (e.g., a filler key, non-driving key). Thus, the half size keyway 124B is approximately half of a radial dimension (e.g., depth) as compared with the full size keyway 124A, and the half size key 126B is approximately half of a radial dimension (e.g., thickness) as compared with the full size key 126A. While the full size keyway 124A and the full size key 126A are utilized to enable a mechanical connection between the rotor 52 and the shaft 54, the half size key way 124B and the half size key 126B are configured to hold weight to mechanically balance the rotor 52 and shaft 54 without providing any mechanical connection between the rotor 52 and the shaft 54. As such, the half size key way 124B and the half size key 126B may be on the opposite radial side of the rotor 52 and shaft 54 from the full size key way 124 A and the full size key 126A.

[0042] In certain embodiments, the keys (e.g., 126A, 126B) may include a spring key designed to provide a spring force in a radial direction to help retain the spring key in the corresponding keyway (e.g., 124A, 124B). For example, the spring key may be an axial key (e.g., an elongated bar of metal) having a curvature in the axial direction (e.g., concave key), thereby providing the spring force in the radial direction. In certain embodiments, the keys (e.g., 126A, 126) also may be sized to provide equal mass in the keyway entry portions 121 (121A, 121B) for improved mass balance. In some embodiments, the keyway entry portions 121 (121A, 121B) may be excluded to help provide an equal mass along the shaft 54 and the rotor 52.

[0043] FIG. 6 is a schematic cross-sectional view of the induction motor 20 of the motor section 16 of the ESP system 10 of FIGS. 1-5, further illustrating internal components of the ESP system 10. The motor section 16 may include a head 90, described more in FIG. 7, and a shaft section 130. The shaft section 130 may include the components described in FIG. 2, with the shaft 54 running through the axial length of the motor section 16. FIG. 6 further illustrates the arrangement of the bearings 70 and rotors 52 to enable high-speed operation of the induction motor 20.

[0044] Around the shaft 54 at various intervals or stages are rotors 52 (e.g., staged rotor section 132), which circumferentially surrounds the shaft 54 and drives rotation of the shaft 54 when the ESP system 10 is operable. The copper end rings 59 of the rotor copper cage 58 are disposed at the axially opposite ends of each rotor 52, wherein the rotor copper cage 58 is configured to induce a magnetic field to rotate the rotors 52 in the induction motor 20. The bearings 70 are disposed adjacent the copper end rings 59 of the rotors 52. In the illustrated embodiment, the bearings 70 are disposed at axially opposite ends of each of the rotors 52 (e.g., adjacent the copper end rings 59), such that the bearings 70 are both axially between adjacent rotors 52 and also at the axially opposite ends 134 of the staged rotor section 132. As further illustrated, the stator 56 surrounds the rotors 52 and bearings 70. In the illustrated embodiment, one stator 56 surrounds all of the rotors 52. However, in other embodiments, the induction motor 20 includes a plurality of stators 56, such as a stator 56 corresponding to each rotor 52. [0045] FIG. 7 is an illustrated embodiment of the head 90 of the motor section 16 of FIG. 6. The quick connector 80 may be located on the head 90 to direct power from the power cable 18 to the motor section 16 to power the induction motor 20. A power cable extends internally through the motor section 16 from the quick connector 80 to the stator 56. In the illustrated embodiment, the head 90 include various features to facilitate rotation, lubrication, and stability of the shaft 54.

[0046] For example, the head 90 includes a bearing 170 (e.g., annular bearing) disposed about the shaft 54 within a bearing support portion 174 (e.g., annular bearing support). The bearing 170 may include any type of bearing similar to the bearing 70 as described in detail above. The head 90 also includes a thrust bearing 176 disposed between an annular shoulder 178 of the bearing support portion 174 and a retainer 180 (e.g., annular retainer) coupled to an end portion 182 of the shaft 54. The retainer 180 may include a threaded nut coupled to external threads of the shaft 54, a lock ring, a lock pin, or any combination thereof.

[0047] The head 90 also includes a lubrication system 184 having a lubricant circuit 186 coupled to a lubricant port 188, wherein the lubricant circuit 186 includes lubricant passages 190, 192, and 194. The lubricant port 188 also includes a lubricant injection fitting 196 configured to seal the lubricant circuit 186 and enable injection of a lubricant into the lubricant circuit 186. The lubricant passage 190 extends to an internal rotor chamber 198 having the bearings 70 and the rotors 52. The lubricant passage 192 extends to the bearing 170. The lubricant passage 194 extends to the thrust bearing 176.

[0048] Technical effects of the disclosed embodiments include improvements in an induction motor 20 to enable high-speed operation, such as high rotational speeds up to 12,000 rpm, for reliable continuous operation of an ESP system 10. The induction motor 20 may include rotors 52 having a shorter length than conventional motors of ESP systems, thereby reducing the mass of each rotor 52 and enabling closer spacing of bearings 70. The reduced mass and closer spacing of bearings 70 helps to maintain stability and reduce vibration at the high rotational speeds. The bearings 70 also may be designed as self-lubricating bearings with improved high-speed operation. The induction motor 20 also may include tighter tolerances and improved mass balance of the rotors 52 and the shaft 54, such as by ensuring that substantially equal masses are within any keyways between the rotors 52 and the shaft 54. Additionally, the embodiments discussed herein include a controller 72 configured to monitor feedback from various sensors throughout the induction motor 20 for any issues during highspeed operation (e.g., high temperatures, high pressures, high vibration, etc.), and automatically execute one or more control actions to protect the induction motor 20 against any unnecessary wear or damage. Thus, the embodiments discussed herein substantially broaden the operational range of ESP systems 10 by enabling rotational speeds from low to high rotational speeds, such as 1000 to 12000 rpm.

[0049] The subject matter described in detail above may be defined by one or more clauses, as set forth below.

[0050] A system includes an induction motor configured to drive an electric submersible pump (ESP). The induction motor includes a one or more rotors disposed about a rotational axis, and a plurality of bearings disposed about the rotational axis. Each bearing of the plurality of bearings is disposed axially between a pair of rotors of the one or more rotors. The induction motor further includes one or more stators disposed about the one or more rotors.

[0051] The system of any preceding clause, including the ESP coupled to the induction motor.

[0052] The system of any preceding clause, wherein an axial length of each rotor of the one or more rotors is less than or equal to 15 inches.

[0053] The system of any preceding clause, wherein a length to diameter ratio of each rotor of the one or more rotors is between 3.5 and 9.

[0054] The system of any preceding clause, wherein an outer diameter of each rotor of the one or more rotors is less than or equal to 3 inches.

[0055] The system of any preceding clause, wherein the induction motor is configured to operate at a rotational speed up to a high speed of at least 4,000 rpm.

[0056] The system of any preceding clause, wherein the induction motor is configured to operate at a rotational speed from a low speed of 4,000 rpm to a high speed of 12,000 rpm.

[0057] The system of any preceding clause, wherein the one or more rotors includes at least ten rotors, and each rotor of the one or more rotors is disposed between first and second bearings of the plurality of bearings at opposite first and second axial ends of the respective rotor.

[0058] The system of any preceding clause, wherein the induction motor further includes a thrust bearing and an additional bearing at an axial distance away from the one or more rotors.

[0059] The system of any preceding clause, wherein each bearing of the plurality of bearings includes a metal-polymer low friction bearing.

[0060] The system of any preceding clause, wherein the one or more stators include a single stator disposed about all of the one or more rotors.

[0061] The system of any preceding clause, wherein the one or more stators include a plurality of stator stacks, and each of the plurality of stator stacks is disposed about one of the one or more rotors.

[0062] The system of any preceding clause, further including a shaft extending through the one or more rotors and the plurality of bearings. The system further includes a plurality of keyways extending along the shaft, wherein at least one first keyway of the plurality of keyways aligns with a corresponding keyway in a rotor of the one or more rotors, and at least one second key way of the plurality of key ways does not align with a corresponding keyway in a rotor of the one or more rotors. The system further includes a driving key disposed in a full keyway defined by the at least one first keyway and the corresponding keyway, wherein the driving key is configured to transfer torque between the rotor and the shaft. The system further includes a filler key disposed in a partial keyway defined only by the at least one second keyway, wherein the filler key is configured to improve a mass balance of the shaft and the one or more rotors.

[0063] The system of any preceding clause, wherein the driving key, the filler key, or both, includes a spring key configured to apply a radial spring force.

[0064] The system of any preceding clause, including a controller having a processor, a memory, and instructions stored on the memory and executable by the processor to operate the induction motor up to a high speed, monitor feedback from one or more sensors configured to monitor operation of the induction motor at the high speed, and adjust one or more operating parameters of the induction motor to protect the induction motor in response to the feedback.

[0065] A method includes driving an electric submersible pump (ESP) with an induction motor. The induction motor includes a one or more rotors disposed about a rotational axis and a plurality of bearings disposed about the rotational axis, wherein each bearing of the plurality of bearings is disposed axially between a pair of rotors of the one or more rotors. The induction motor further includes one or more stators disposed about the one or more rotors.

[0066] The method of the preceding clause, comprising controlling the induction motor to rotate at a high speed up to at least 10,000 rpm.

[0067] The method of any preceding clause, further including monitoring feedback from one or more sensors configured to monitor operation of the induction motor at the high speed, and adjusting one or more operating parameters of the induction motor to protect the induction motor in response to the feedback.

[0068] A system includes a rotor of a plurality of rotors of an induction motor configured to drive an electric submersible pump (ESP). The rotor includes a lamination, a plurality of copper bars disposed in the lamination, and first and second copper end rings coupled to the plurality of copper bars at axially opposite ends of the rotor. The rotor has an axial length that is less than or equal to 20 inches.

[0069] The system of the preceding clause, further including a shaft extending through the rotor. The system further includes a plurality of keyways extending along the shaft, wherein at least one first keyway of the plurality of keyways aligns with a corresponding keyway in the rotor, and at least one second keyway of the plurality of keyways does not align with a corresponding keyway in the rotor. The system further includes a driving key disposed in a full keyway defined by the at least one first keyway and the corresponding key way, wherein the driving key is configured to transfer torque between the rotor and the shaft. The system further includes a filler key disposed in a partial keyway defined only by the at least one second keyway, wherein the filler key is configured to improve a mass balance of the shaft and the rotor.

[0070] An induction motor for an electronic submersible pump (ESP) system, including a one or more rotors disposed along a length of a shaft, each rotor of the one or more rotors having a corresponding stator. [0071] The induction motor of the preceding clause, wherein a length-to-diameter ratio of each rotor of the one or more rotors is optimized to produce low vibration during operation.

[0072] The induction motor of any preceding clause, further including keyways on opposing sides along the length of the shaft for balancing the shaft during operation.

[0073] While only certain features have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the disclosure.

[0074] The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for (perform)ing (a function)...” or “step for (perform)ing (a function)...”, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).

Claims

1. A system, comprising: an induction motor configured to drive an electric submersible pump (ESP), wherein the induction motor comprises: one or more rotors disposed about a rotational axis; a plurality of bearings disposed about the rotational axis, wherein each bearing of the plurality of bearings is disposed axially between a pair of rotors of the one or more rotors; and one or more stators disposed about the one or more rotors.

2. The system of claim 1, comprising the ESP coupled to the induction motor.

3. The system of claim 1, wherein an axial length of each rotor of the one or more rotors is less than or equal to 15 inches.

4. The system of claim 1, wherein a length to diameter ratio of each rotor of the one or more rotors is between 3.5 and 9.

5. The system of claim 4, wherein an outer diameter of each rotor of the one or more rotors is less than or equal to 3 inches.

6. The system of claim 1, wherein the induction motor is configured to operate at a rotational speed up to a high speed of at least 4,000 rpm.

7. The system of claim 1, wherein the induction motor is configured to operate at a rotational speed from a low speed of 4,000 rpm to a high speed of 12,000 rpm.

8. The system of claim 1, wherein one or more rotors includes one or more rotors, and each rotor of the one or more rotors is disposed between first and second bearings of the plurality of bearings at opposite first and second axial ends of the respective rotor.

9. The system of claim 8, wherein the induction motor further comprises a thrust bearing and an additional radial bearing at an axial distance away from the one or more rotors.

10. The system of claim 1, wherein each bearing of the plurality of bearings comprises a metal-polymer low friction bearing.

11. The system of claim 1, wherein the one or more stators comprise a single stator disposed about all of the one or more rotors.

12. The system of claim 1, wherein the one or more stators comprise a plurality of stators, and each of the plurality of stators is disposed about one of the one or more rotors.

13. The system of claim 1, comprising: a shaft extending through the one or more rotors and the plurality of bearings; a plurality of keyways extending along the shaft, wherein at least one first keyway of the plurality of keyways aligns with a corresponding keyway in a rotor of the one or more rotors, and at least one second key way of the plurality of key ways does not align with a corresponding key way in a rotor of the one or more rotors; a driving key disposed in a full keyway defined by the at least one first keyway and the corresponding key way, wherein the driving key is configured to transfer torque between the rotor and the shaft; a filler key disposed in a partial keyway defined only by the at least one second key way, wherein the filler key is configured to improve a mass balance of the shaft and the one or more rotors.

14. The system of claim 13, wherein the driving key, the filler key, or both, comprises a spring key configured to apply a radial spring force.

15. The system of claim 1, comprising a controller having a processor, a memory, and instructions stored on the memory and executable by the processor to operate the induction motor up to a high speed, monitor feedback from one or more sensors configured to monitor operation of the induction motor at the high speed, and adjust one or more operating parameters of the induction motor to protect the induction motor in response to the feedback.

16. A method, comprising: driving an electric submersible pump (ESP) with an induction motor, wherein the induction motor comprises: a one or more rotors disposed about a rotational axis; a plurality of bearings disposed about the rotational axis, wherein each bearing of the plurality of bearings is disposed axially between a pair of rotors of the one or more rotors; and one or more stators disposed about the one or more rotors.

17. The method of claim 16, comprising controlling the induction motor to rotate at a high speed up to at least 10,000 rpm.

18. The method of claim 17, comprising: monitoring feedback from one or more sensors configured to monitor operation of the induction motor at the high speed; and adjusting one or more operating parameters of the induction motor to protect the induction motor in response to the feedback.

19. A system, comprising: a rotor of a plurality of rotors of an induction motor configured to drive an electric submersible pump (ESP), wherein the rotor comprises: a lamination; a plurality of copper bars disposed in the lamination; and first and second copper end rings coupled to the plurality of copper bars at axially opposite ends of the rotor, wherein an axial length of the rotor is less than or equal to 12 inches.

20. The system of claim 19, comprising: a shaft extending through the rotor; a plurality of keyways extending along the shaft, wherein at least one first keyway of the plurality of keyways aligns with a corresponding keyway in the rotor, and at least one second keyway of the plurality of keyways does not align with a corresponding keyway in the rotor; a driving key disposed in a full keyway defined by the at least one first keyway and the corresponding key way, wherein the driving key is configured to transfer torque between the rotor and the shaft; a filler key disposed in a partial keyway defined only by the at least one second key way, wherein the filler key is configured to improve a mass balance of the shaft and the rotor.