Electric submersible pumps

Abstract

A method of pumping wellbore fluid, comprising the steps of: installing an electric submersible pump in a wellbore; and operating the pump at more than 4,500 rpm to pump the wellbore fluid. Pumping in this manner provides a number of advantages in use in that the required high-speed motor and pump is shorter for a given power than existing arrangements, and provides increased reliability due to reduced complexity. A much shorter motor/pump combination also allows such equipment to be used in deviated boreholes with a reduction in damage due to mishandling and bending, as well as facilitating assembly and testing in the manufacturer's plant.

1 . A motor, comprising:
 a rotor comprising:
 a central shaft; 
 a carrier sleeve ( 203 ) loosely fitted on the central shaft ( 201 ); and 
 support rings closely engaging the shaft and supporting the carrier sleeve; and 
   a stator coaxial with the rotor, comprising:
 a stack of laminations; and 
 radially spaced coils wound around the stack. 
   
   
   
       2 . The motor according to  claim 1 , wherein the carrier sleeve is keyed to the shaft to prevent relative rotation between the carrier sleeve and the shaft. 
   
   
       3 . The motor according to  claim 2 , wherein the rotor further comprises a key extending outwardly from the shaft and engaging complementary locating portions of the carrier sleeve and associated support ring to prevent relative rotation between the carrier sleeve, the support ring, and the shaft. 
   
   
       4 . The motor according to  claim 3 , wherein the key is of relatively short length by comparison with the length of the carrier sleeve. 
   
   
       5 . The motor according to  claim 1 , wherein the rotor further comprises a plurality of carrier sleeves provided at axially spaced locations along the shaft, the carrier sleeves rotationally locked to the shaft. 
   
   
       6 . The motor according to  claim 5 , wherein:
 the carrier sleeves are supported on the shaft by the support rings,   the carrier sleeves and the support rings alternate on the shaft, and   the rotor further comprises a retainer constraining the carrier sleeves and support rings on the shaft.   
   
   
       7 . The motor according to  claim 1 , further comprising:
 a tubular housing; and   bearings disposed in the housing,   wherein the shaft is supported by the bearings.   
   
   
       8 . The motor according to  claim 7 , wherein the bearings are disposed between the support rings and an inside bore wall of the stator. 
   
   
       9 . The motor according to  claim 1 , wherein the rotor further comprises a plurality of permanent magnets mounted on the carrier sleeve and equiangularly spaced about the shaft. 
   
   
       10 . The motor according to  claim 1 , further comprising
 a bearing mounting the rotor to the stator;   a resiliently biased projection disposed on one of the stator and the bearing; and   a receiver disposed on the other of the stator and the bearing,   wherein the projection is operable, by rotation of the rotor, to engage the receiver, thereby rotationally coupling the bearing and the stator.   
   
   
       11 . The motor according to  claim 10 , wherein the projection is provided on the outer of the stator and the bearing and the receiver is provided in the inner of the stator and the bearing. 
   
   
       12 . The motor according to  claim 1 , further comprising:
 a housing, wherein the stator is mounted in the housing;   an axial groove formed in one of the stator and the housing; and   an axial key engaging the axial groove, thereby rotationally coupling the housing and the stator.   
   
   
       13 . The motor according to  claim 1 , wherein the motor is an AC synchronous permanent magnet motor. 
   
   
       14 . The motor according to  claim 1 , wherein the motor is capable of reliably operating at speeds greater than 4,500 rpm. 
   
   
       15 . An electric submersible pump incorporating a motor according to  claim 1 . 
   
   
       16 . A motor comprising:
 a rotor;   a stator coaxial with the rotor;   a bearing mounting the rotor to the stator;   a resiliently biased projection disposed on one of the stator and the bearing; and   a receiver disposed on the other of the stator and the bearing,   wherein the projection is operable, by rotation of the rotor, to engage the receiver, thereby rotationally coupling the bearing and the stator.   
   
   
       17 . The motor according to  claim 16 , wherein the projection is provided on the outer of the stator and the bearing, and the receiver is provided in the inner of the stator and the bearing. 
   
   
       18 . A motor comprising:
 a rotor;   a housing;   a stator coaxial with the rotor and mounted in the housing;   an axial groove formed in one of the stator and the housing; and   an axial key engaging the axial groove, thereby rotationally coupling the housing and the stator.   
   
   
       19 . A motor comprising:
 an annular stator;   a bearing disposed within the stator and having a peripheral outer surface and an axial groove formed in the peripheral outer surface;   a rotor mounted in the bearing and disposed within the stator;   a resiliently biased projection extending from an inner peripheral surface of the stator;   wherein the projection is operable, by rotation of the rotor, to engage the groove, thereby rotationally coupling the bearing and the stator.   
   
   
       20 . The motor according to  claim 19 , wherein the projection is provided within a recess in the inner peripheral surface of the stator. 
   
   
       21 . The motor according to  claim 19 , further comprising a retainer rotationally coupling the projection and the stator. 
   
   
       22 . The motor according to  claim 19 , wherein the projection is resiliently biased so as to be capable of being retracted against a spring force to allow insertion of the bearing. 
   
   
       23 . The motor according to  claim 19 , wherein the projection is a spring clip. 
   
   
       24 . The motor according to  claim 19 , wherein the projection is an open circular spring. 
   
   
       25 . The motor according to  claim 19 , wherein the projection is a spring loaded pin. 
   
   
       26 . The motor according to  claim 19 , wherein the projection is a cantilever. 
   
   
       27 . The motor according to  claim 19 , wherein the projection is disposed within a solid block disposed between laminations of the stator. 
   
   
       28 . The motor according to  claim 19 , wherein the rotor and the bearing are mounted on a central shaft coaxial with the rotor and the stator. 
   
   
       29 . The motor according to  claim 28 , wherein the rotor comprises a plurality of rotor parts spaced along the shaft with bearings therebetween. 
   
   
       30 . The motor according to  claim 19 , wherein the rotor comprises a plurality of permanent magnets. 
   
   
       31 . The motor according to  claim 19 , further comprising:
 a housing, wherein the stator is mounted in the housing;   an axial groove formed in one of the stator and the housing; and   an axial key engaging the axial groove, thereby rotationally coupling the housing and the stator.   
   
   
       32 . The motor according to  claim 19 , wherein the motor is an AC synchronous permanent magnet motor. 
   
   
       33 . The motor according to  claim 19 , wherein the motor is capable of reliably operating at speeds greater than 4,500 rpm. 
   
   
       34 . An electric submersible pump incorporating the motor according to  claim 19 . 
   
   
       35 . A downhole elongate motor adapted to fit within an elongate bore, the motor comprising:
 a rotor;   a stator coaxial with the rotor, and comprising:
 a tubular housing; 
 a stator core disposed in the housing and comprising:
 a stack of laminations having slots; and 
 windings formed on the laminations; 
 
 a groove formed in the housing and extending along the length of the housing; and 
 an axial key engaging the groove, thereby rotationally coupling the housing and the stator core. 
   
   
   
       36 . The downhole elongate motor according to  claim 35 , wherein axial grooves are provided in both the stator core and the housing, and the axial key engages within both axial grooves. 
   
   
       37 . The downhole elongate motor according to  claim 35 , wherein the axial key is in the form of an integral raised feature on the stator core that engages within the axial groove in the housing. 
   
   
       38 . The downhole elongate motor according to  claim 35 , wherein the stator core is locked within the housing by a series of axial keys engaging within the groove in the housing. 
   
   
       39 . The downhole elongate motor according to  claim 38 , wherein the stator core comprises a series of stator sections axially spaced within the housing, each stator section being locked within the housing by a respective one of the axial keys engaging within the axial groove. 
   
   
       40 . The downhole elongate motor according to  claim 35 , wherein the stator core comprises a series of stator sections axially spaced within the housing ( 202 ) and separated by bearing surfaces, the bearing surfaces being provided to support the rotor within the stator. 
   
   
       41 . The downhole elongate motor according to  claim 35 , wherein the motor is an AC synchronous permanent magnet motor. 
   
   
       42 . The downhole elongate motor according to  claim 35 , wherein the motor is capable of operating at speeds greater than 4,500 rpm. 
   
   
       43 . The downhole submersible pump incorporating an elongate motor according to  claim 35 . 
   
   
       44 . A method of fabricating a stator of an elongate downhole motor adapted to fit within an elongate bore, the motor having a rotor and a stator coaxial with the rotor, the method comprising:
 forming a stator core by installing windings within slots in a stack of laminations; and   coaxially inserting the stator core with the windings thereon into a tubular housing, wherein the stator core is locked within the housing by an axial key engaging a groove formed in the housing and extending along the length of the housing, thereby preventing the laminations from turning relative to the housing during operation of the motor.   
   
   
       45 . The method according to  claim 44 , wherein an outside surface of the stator core is ground prior to being inserted into the housing. 
   
   
       46 . The method according to  claim 44 , wherein the windings are formed within the slots in the stack of laminations by threading wire through the slots. 
   
   
       47 . The method according to  claims 46 , wherein a mandrel incorporating rebates is inserted within a bore in the stator core to centre the laminations prior to the windings being formed within the slots in the stack of laminations. 
   
   
       48 . The method according to any one of  claims 44 , wherein the elongate motor is incorporated into a downhole submersible pump.