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 permanent magnet motor comprising:
 a rotor, comprising:
 a central shaft; and 
 a plurality of permanent magnets having axial ends; 
 a carrier sleeve mounted on the shaft and bearing the magnets; 
 a retention sleeve extending over the magnets; and 
 at least one stress-relieving radially outwardly extending abutment part on the carrier sleeve abutting an adjacent axial end of the magnets, 
 wherein the retention sleeve has at least one end portion turned in over the abutment part to retain the magnets in position on the carrier sleeve without damaging the axial end of the magnet. 
   
   
   
       2 . The motor according to  claim 1 , wherein:
 the rotor comprises a second outwardly extending abutment part on the carrier sleeve abutting an adjacent axial end of the magnets, and   a second end portion of the retention sleeve is turned in over the second abutment part to retain the magnets in position on the carrier sleeve.   
   
   
       3 . The motor according to  claim 1 , wherein the abutment part comprises a ring engaging a shoulder on the carrier sleeve. 
   
   
       4 . The motor according to  claim 1 , wherein the rotor further comprises a plurality of tubular elements supporting the permanent magnets and spaced axially along the shaft. 
   
   
       5 . The motor according to  claim 1 , further comprising:
 a stator coaxial with the rotor and comprising:
 a stack of laminations; and 
 radially spaced coils wound around the stack. 
   
   
   
       6 . The motor according to  claim 1 , wherein the motor is an AC synchronous permanent magnet motor. 
   
   
       7 . The motor according to  claim 1 , wherein the motor is capable of reliably operating at speeds greater than 4,500 rpm. 
   
   
       8 . The motor according to  claim 1 , wherein:
 the carrier sleeve is loosely fitted on the shaft, and   the rotor further comprises support rings closely engaging the shaft and supporting the carrier sleeve.   
   
   
       9 . The motor according to  claim 8 , wherein the carrier sleeve is keyed to the shaft to prevent relative rotation between the carrier sleeve and the shaft. 
   
   
       10 . The motor according to  claim 9 , wherein a key extends outwardly from the shaft and engages 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. 
   
   
       11 . The motor according to  claim 1 , wherein the plurality of permanent magnets is equiangularly spaced about the shaft. 
   
   
       12 . The motor according to  claim 1 , wherein the permanent magnets incorporate axially laminated parts to reduce eddy current losses. 
   
   
       13 . 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.   
   
   
       14 . The motor according to  claim 13 , wherein the projection is provided on the outer of the stator and the bearing, and the receiver is provided on the inner of the stator and the bearing. 
   
   
       15 . 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.   
   
   
       16 . The motor according to  claim 1 , wherein the abutment part comprises a snap ring disposed within a groove in the carrier sleeve. 
   
   
       17 . The motor according to  claim 1 , wherein the retention sleeve is deformed into a detent on the outer surface of the abutment part. 
   
   
       18 . An electric submersible pump incorporating a permanent magnet motor according to  claim 1 .