Electric submersible motor oil expansion compensator

Abstract

An electric submersible pumping system includes a motor that is filled with motor lubricant fluid and a pump driven by the motor. The electric submersible pumping system further includes a fluid expansion module connected to the motor that is designed to accommodate the expansion and contraction of the motor lubricant fluid in the motor. The fluid expansion module preferably includes a piston seal housing in fluid communication with the motor and a bag seal housing in fluid communication with the piston seal housing. The fluid expansion module further includes at least one axially movable barrier in the piston seal housing and at least one expansible barrier in the bag seal housing. The axially movable barrier and the expansible barrier cooperate to permit the expansion of the motor lubricant fluid without contaminating the motor lubricant fluid with fluids or and solids from the wellbore.

What is claimed is: 
     
         1 . An electric submersible pumping system for use in pumping fluids from a wellbore, the electric submersible pumping system comprising:
 a motor;   a pump driven by the motor; and   a fluid expansion module connected to the motor, wherein the fluid expansion module comprises:
 a piston seal housing; and 
 a first piston assembly contained within the piston seal housing, wherein the first piston assembly is configured for sliding engagement within the piston seal housing. 
   
     
     
         2 . The electric submersible pumping system of  claim 1 , wherein the fluid expansion module further comprises a second piston assembly contained within the piston seal housing, wherein the second piston assembly is configured for sliding engagement within the piston seal housing. 
     
     
         3 . The electric submersible pumping system of  claim 2 , wherein each of the first and second piston assemblies comprises:
 a piston; and   at least one seal positioned around the outside of the piston.   
     
     
         4 . The electric submersible pumping system of  claim 3 , wherein each seal further comprises:
 a body; and   an interior spring, wherein the interior spring is configured to exert an outward radial force against the body.   
     
     
         5 . The electric submersible pumping system of  claim 4 , wherein the piston seal housing includes a polymer liner. 
     
     
         6 . The electric submersible pumping system of  claim 1 , wherein the fluid expansion module further comprises:
 a bag seal housing; and   a bag seal assembly within the bag seal housing.   
     
     
         7 . The electric submersible pumping system of  claim 6 , wherein the bag seal assembly further comprises:
 a bag support; and   a bladder secured to the bag support.   
     
     
         8 . The electric submersible pumping system of  claim 7 , wherein the bag seal assembly further comprises one or more discharge ports and wherein each of the one or more discharge ports is configured as a one-way check valve that places the interior of the bladder in fluid communication with the wellbore when opened. 
     
     
         9 . The electric submersible pumping system of  claim 1 , wherein the fluid expansion module further comprises a fluid exchange assembly and wherein the fluid exchange assembly comprises:
 a solids screen;   exchange ports; and   wherein the fluid exchange assembly is configured to place the exterior of the bladder in fluid communication with the wellbore.   
     
     
         10 . The electric submersible pumping system of  claim 1 , further comprising a seal section between the motor and the pump, wherein the seal section comprises:
 a shaft;   one or more mechanical seals; and   one or more relief valves.   
     
     
         11 . The electric submersible pumping system of  claim 10 , wherein each of the one or more mechanical seals comprises:
 a runner connected to the seal section shaft; and   a stationary ring in contact with the runner.   
     
     
         12 . A system for accommodating the expansion of motor lubricant in a motor within an electric submersible pump used for removing fluids from a wellbore, the system comprising:
 a seal section connected to the motor; and   a fluid expansion module connected to the motor, wherein the fluid expansion module has a longitudinal axis and wherein the fluid expansion module comprises:
 at least one piston assembly, wherein the at least one piston assembly moves along the longitudinal axis of the fluid expansion module in response to an expansion of the motor lubricant; and 
 a bag seal assembly, wherein the bag seal assembly includes a bladder that expands in response to movement of the at least one piston assembly. 
   
     
     
         13 . The system of  claim 12 , wherein the fluid expansion module further comprises a fluid exchange assembly that places the exterior of the bladder in fluid communication with the wellbore. 
     
     
         14 . The system of  claim 12 , wherein the seal section comprises:
 a seal section shaft; and   one or more mechanical seals connected to the seal section shaft.   
     
     
         15 . The system of  claim 15 , wherein the seal section further comprises at least one relief valve that is configured to release motor lubricant to the wellbore. 
     
     
         16 . An electric submersible pumping system configured to pump fluids from a wellbore, the electric submersible pumping system comprising:
 a motor; wherein the motor is filled with motor lubricant fluid;   a pump driven by the motor; and   a fluid expansion module connected to the motor, wherein the fluid expansion module comprises:
 a piston seal housing in fluid communication with the motor; 
 a bag seal housing in fluid communication with the piston seal housing; 
 at least one axially movable barrier in the piston seal housing; and 
 at least one expansible barrier in the bag seal housing. 
   
     
     
         17 . The electric submersible pumping system of  claim 16 , wherein the at least one axially movable barrier in the piston seal housing comprises a piston assembly. 
     
     
         18 . The electric submersible pumping system of  claim 17 , wherein the at least one expansible barrier in the bag seal housing comprises a bladder. 
     
     
         19 . The electric submersible pumping system of  claim 18 , wherein the bladder has an interior that is in fluid communication with the piston seal housing and an exterior that is in fluid communication with the wellbore.