Submersible pumping system with heat transfer mechanism

Abstract

A submersible pumping system for downhole use in extracting fluids containing hydrocarbons from a well. In one embodiment, the pumping system comprises a rotary induction motor, a motor casing, one or more pump stages, and a cooling system. The rotary induction motor rotates a shaft about a longitudinal axis of rotation. The motor casing houses the rotary induction motor such that the rotary induction motor is held in fluid isolation from the fluid being extracted. The pump stages are attached to the shaft outside of the motor casing, and are configured to impart fluid being extracted from the well with an increased pressure. The cooling system is disposed at least partially within the motor casing, and transfers heat generated by operation of the rotary induction motor out of the motor casing.

What is claimed is: 
     
         1 . A submersible pumping system for downhole use in extracting fluids from a well, the pumping system comprising:
 a rotary induction motor, the rotary induction motor including:
 a rotor; and 
 a stator disposed about the rotor and configured to generate a magnetic field within the rotary induction motor that drives the rotor; 
   a motor casing that houses the rotary induction motor such that the rotary induction motor is held in fluid isolation from the fluid being extracted;   a shaft extending from the motor casing, the shaft being formed with or coupled to the rotor such that the rotor drives the shaft to rotate about an axis of rotation that runs longitudinally through the pumping system;   one or more pump stages attached to the shaft outside of the motor casing, the one or more pump stages being configured to impart fluid being extracted from the well with an increased pressure; and   a fluid pump disposed within the motor casing, the fluid pump being configured to circulate a reservoir of internal fluid within the motor casing to form a convective thermal coupling between working components of the rotary induction motor and the motor casing,   wherein the reservoir of internal fluid is held internally within the motor casing, and   wherein the stator and the motor casing are configured such that multiple flow channels are formed between the motor casing and the stator, the flow channels being formed at least in part by an internal surface of the motor casing and an outer surface of the stator, and the flow channels convey flows of the internal fluid generated by the fluid pump between the stator and the motor casing.   
     
     
         2 . The pumping system of  claim 1 , wherein the flow channels run transverse to a plane that is perpendicular to the axis of rotation. 
     
     
         3 . The pumping system of  claim 2 , wherein the flow channels run generally parallel to the axis of rotation. 
     
     
         4 . The pumping system of  claim 1 , wherein the flow channels are formed along predetermined convective pathways designed to enhance the transfer of heat from the stator to the motor casing. 
     
     
         5 . The pumping system of  claim 1 , wherein the flow channels are further formed at least on part by one or more structures that secure the stator in place with respect to the motor casing. 
     
     
         6 . The pumping system of  claim 1 , wherein the flow channels are formed such that an effective convective heat transfer coupling is formed between the circulating internal fluid and the portions of the motor casing that bound on the flow channels. 
     
     
         7 . The pumping system of  claim 1 , further including a reservoir for the internal fluid formed within the motor casing apart from the stator, the reservoir being of sufficient volume to act as a heat sink for heat generated around the rotor and the stator as the heat is carried away from the rotor and the stator by the internal fluid flowing through the flow channels. 
     
     
         8 . The pumping system of  claim 7 , wherein the volume of the reservoir of internal fluid is at least about 1 liter. 
     
     
         9 . The pumping system of  claim 7 , wherein the volume of the reservoir of internal fluid is at least about 2 liters. 
     
     
         10 . The pumping system of  claim 7 , wherein the volume of the reservoir of internal fluid is at least about 3 liters.