Method and apparatus to control water migration into electrical submersible pump motors

Abstract

A seal assembly for an electrical submersible pumping system that communicates downhole pressure to a pump motor and seals wellbore fluids from the motor. The seal assembly includes a chamber circumscribing a pump shaft and a bladder in the chamber. The outer surface of the bladder is in fluid communication with the wellbore fluid. The inside of the bladder contains dielectric fluid that is ported to the pump motor in an annulus between the pump shaft and a sleeve. A water absorbing elastomer is disposed inside of the bladder for absorbing water that may migrate into the bladder from the wellbore.

1 . An electrical submersible pump assembly disposable within a wellbore comprising:
 a motor having dielectric fluid;   a pump coupled to the motor;   a seal section having dielectric fluid that is in communication with the dielectric fluid in the motor; and   an absorption assembly disposed in the seal section, so that when moisture migrates into the seal section, the moisture is absorbed by the absorption assembly.   
     
     
         2 . The electrical submersible pump assembly of  claim 1 , further comprising a bladder in the seal section that defines a barrier between fluid from the wellbore and dielectric fluid in the seal and in the motor. 
     
     
         3 . The electrical submersible pump assembly of  claim 1 , wherein the absorption assembly comprises an elastomer secured to a mount. 
     
     
         4 . The electrical submersible pump assembly of  claim 3 , wherein the absorbing material comprises a hydrophilic elastomer. 
     
     
         5 . The electrical submersible pump assembly of  claim 3 , wherein the absorbing material circumscribes a shaft coupling the pump and motor and defines an annular shape. 
     
     
         6 . The electrical submersible pump assembly of  claim 1 , further comprising a composite bladder made up of hydrophobic elastomer on an outer surface of the bladder, and hydrophilic elastomer on an inner surface of the bladder. 
     
     
         7 . The electrical submersible pump assembly of  claim 1 , wherein the absorption assembly comprises a hydrophilic elastomer and is strategically located in an expected flow path of moisture from fluid from the wellbore and the motor. 
     
     
         8 . An electrical submersible pump assembly disposable within a wellbore comprising:
 a housing;   a motor;   a pump coupled to the motor by a shaft;   a seal section comprising a flexible bladder with an outer surface in pressure communication with pressure ambient to the housing and an inner surface in pressure communication with the motor; and   a moisture absorbing material disposed in the seal section for absorbing moisture in the seal section.   
     
     
         9 . The electrical submersible pump assembly of  claim 8 , wherein the bladder circumscribes an elongated sleeve coaxially mounted around the shaft, and wherein an annulus is defined between the shaft and sleeve. 
     
     
         10 . The electrical submersible pump assembly of  claim 9 , further comprising a port formed radially through a sidewall of the sleeve, and wherein a flow path is defined between the seal through the port and the annulus. 
     
     
         11 . The electrical submersible pump assembly of  claim 8 , further comprising a cylindrical bulkhead inside the housing, and wherein the moisture absorbing material comprises an annular member coupled to the bulkhead. 
     
     
         12 . A method of pumping fluid from a wellbore comprising:
 a. providing a submersible pumping system comprising a motor, a pump coupled with the motor, a seal section for equalizing pressure in the motor with pressure ambient to the motor, and dielectric fluid in the seal, in the motor, and in a passage extending between the seal and the motor; and   b. providing a moisture absorbing material in the dielectric fluid and in a location that is in an expected path of moisture flow from ambient to the housing and to the motor, so that when wellbore fluid from the wellbore leaks into the dielectric fluid, moisture in the wellbore fluid is absorbed in the moisture absorbing material; and   c. inserting the submersible pumping system into the wellbore and activating the motor to operate the pump.   
     
     
         13 . The method of  claim 12 , wherein the moisture absorbing material is mounted to a bulkhead in the housing and circumscribes the shaft. 
     
     
         14 . The method of  claim 12 , wherein the moisture absorbing material is provided on an inner surface of a flexible bladder in the seal section, and wherein the inner surface of the bladder is in contact with the dielectric fluid and an outer surface of the bladder is in contact with the wellbore fluid. 
     
     
         15 . The method of  claim 14 , wherein a moisture repelling material is provided on an outer surface of the bladder.