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 . An electric submersible pump, comprising:
 a permanent magnet motor, comprising:
 a rotor comprising:
 a central shaft; 
 a plurality of tubular elements spaced axially along the shaft; 
 a plurality of support rings spaced axially along the shaft between the tubular elements and serving to support the tubular elements on the shaft so that the tubular elements are rotatable with the shaft; 
 a plurality of permanent magnets spaced about a circumferential outer surface of each of the tubular elements; 
 a respective retention sleeve tightly fitted over the permanent magnets on each tubular element so as to retain the permanent magnets on the tubular element; and 
 
 a stator coaxial with the rotor, comprising:
 a stack of laminations; and 
 radially spaced coils wound around the stack. 
 
   
   
   
       2 . The pump according to  claim 1 , wherein the motor is an AC synchronous permanent magnet motor. 
   
   
       3 . The pump according to  claim 1 , wherein the motor is capable of reliably operating at speeds greater than 4,500 rpm. 
   
   
       4 . The pump according to  claim 1 , wherein the shaft of the motor is supported with respect to the stator by bearings located between the support rings and the stator. 
   
   
       5 . The pump according to  claim 4 , wherein the shaft of the motor incorporates lubricating passages for supplying lubricating fluid to the bearings. 
   
   
       6 . The pump according to  claim 4 , wherein the bearings incorporate spiral grooves for promoting the flow of lubricating fluid through the grooves to increase the bearing pressure. 
   
   
       7 . The pump according to  claim 1 , wherein each retention sleeve has turned in end portions for holding the retention sleeve in position on the tubular element. 
   
   
       8 . The pump according to  claim 7 , wherein at least one of the turned in end portions of the retention sleeve is turned in over a stress-relieving radially outwardly extending abutment part comprising a ring engaging a shoulder on the end of the tubular element. 
   
   
       9 . The pump according to  claim 1 , wherein each of the tubular elements is a loose fit on the shaft and is supported on the shaft by the support rings closely engaging the shaft. 
   
   
       10 . The pump according to  claim 1 , wherein each of the tubular elements is keyed to the shaft to prevent relative rotation between the tubular elements and the shaft. 
   
   
       11 . The pump according to  claim 10 , wherein a key extending outwardly from the shaft engages complementary locating portions of the tubular elements and associated support rings to prevent relative rotation between the tubular elements, the support rings and the shaft. 
   
   
       12 . The pump according to  claim 1 , wherein the permanent magnets incorporate axially laminated parts to reduce eddy current losses. 
   
   
       13 . The pump 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 pump according to  claim 13 , 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. 
   
   
       15 . The pump 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.