Linear Hydraulic Pump for Submersible Applications

Abstract

A submersible pumping system has an electric motor, a rotary hydraulic pump driven by the electric motor, and a linear hydraulic pump that is configured to move a production fluid. The rotary hydraulic pump produces a pressurized working fluid that drives the linear hydraulic pump. In another aspect, a method is disclosed for controlling the temperature of an electric motor within a submersible pumping system disposed in a wellbore. The method includes the steps of circulating motor lubricant through a hydraulically driven production pump to reduce the temperature of the motor lubricant.

What is claimed is: 
     
         1 . A submersible pumping system comprising:
 an electric motor;   a rotary hydraulic pump driven by the electric motor, wherein the rotary hydraulic pump produces a pressurized working fluid; and   a linear hydraulic pump that is configured to move a production fluid, wherein the linear hydraulic pump is driven by the pressurized working fluid.   
     
     
         2 . The submersible pumping system of  claim 1 , wherein the rotary hydraulic pump comprises:
 a rotatable pump shaft driven the electric motor;   a plurality of linearly reciprocating piston assemblies; and   a tilt disc assembly connected to the rotatable pump shaft and to the plurality of linearly reciprocating piston assemblies.   
     
     
         3 . The submersible pumping system of  claim 2 , wherein the tilt disc assembly further comprises:
 a drive plate; and   a rocker plate.   
     
     
         4 . The submersible pumping system of  claim 1 , wherein the rotary hydraulic pump comprises:
 a rotatable pump shaft driven the electric motor;   a plurality of linearly reciprocating piston assemblies; and   a camshaft assembly connected to the rotatable pump shaft and to the plurality of linearly reciprocating piston assemblies.   
     
     
         5 . The submersible pumping system of  claim 4 , wherein the camshaft assembly comprises:
 a camshaft;   a plurality of lobes on the camshaft; and   a plurality of connecting rods, wherein each of the plurality of connecting rods is connected to a different one of the plurality of linearly reciprocating piston assemblies.   
     
     
         6 . The submersible pumping system of  claim 5 , wherein the lobes on the camshaft have a stepped profile that causes the plurality of linearly reciprocating piston assemblies to sequentially reciprocate in a manner that produces a progressive cavity within each of the plurality of manifolds. 
     
     
         7 . The submersible pumping system of  claim 1 , wherein the linear hydraulic pump comprises:
 a master cylinder in fluid communication with the pressurized working fluid;   a master piston within the master cylinder;   a slave cylinder in fluid communication with the production fluid; and   a slave piston within the slave cylinder, wherein the slave piston is operably connected to the master piston.   
     
     
         8 . The submersible pumping system of  claim 7 , wherein the linear hydraulic pump further comprises:
 upper and lower injection ports in fluid communication with the master cylinder;   upper and lower vents in fluid communication with the master cylinder;   a lower valve plate; and   an upper valve plate.   
     
     
         9 . The submersible pumping system of  claim 7 , further comprising a pushrod connected between the master piston and the slave piston. 
     
     
         10 . The submersible pumping system of  claim 1 , further comprising a seal section positioned between the pump and the motor. 
     
     
         11 . The submersible pumping system of  claim 1 , further comprising a one or more working fluid lines connected between the rotary hydraulic pump and the linear hydraulic pump, wherein the working fluid lines provide a conduit for the pressurized working fluid. 
     
     
         12 . The submersible pumping system of  claim 11 , wherein the working fluid lines are internal working fluid lines. 
     
     
         13 . The submersible pumping system of  claim 11 , wherein the working fluid lines are external working fluid lines. 
     
     
         14 . A submersible pumping system disposed in a wellbore, the submersible pumping system comprising:
 an electric motor, wherein the electric motor is filled with a motor lubricant fluid;   a hydraulic pump driven by the electric motor, wherein the hydraulic pump increases the pressure of the motor lubricant fluid; and   a production pump configured to produce a production fluid from the wellbore, wherein the production is driven by the pressurized motor lubricant fluid.   
     
     
         15 . The submersible pumping system of  claim 14 , wherein the production pump comprises:
 a master cylinder in fluid communication with the pressurized motor lubricant fluid;   a master piston configured for linear reciprocating movement within the master cylinder;   a slave cylinder in fluid communication with the production fluid; and   a slave piston within the slave cylinder, wherein the slave piston moves in response to the movement of the master piston.   
     
     
         16 . The submersible pumping system of  claim 15 , wherein the production pump further comprises:
 upper and lower injection ports in fluid communication with the master cylinder;   upper and lower vents in fluid communication with the master cylinder;   a lower valve plate; and   an upper valve plate.   
     
     
         17 . The submersible pumping system of  claim 15 , wherein the production pump further comprises a pushrod connected between the master piston and the slave piston. 
     
     
         18 . A method for controlling the temperature of an electric motor within a submersible pumping system disposed in a wellbore, the method comprising the steps of:
 providing an electric motor that is filled with motor lubricant fluid at a first temperature;   driving a hydraulic pump with the electric motor;   pumping the motor lubricant fluid with the hydraulic pump from the electric motor to a production pump;   driving the production pump with the motor lubricant fluid to evacuate a production fluid from the wellbore; and   providing the return of the motor lubricant fluid from the production pump to the electric motor at second temperature that is lower than the first temperature.   
     
     
         19 . The method of  claim 18 , wherein the step of pumping the motor lubricant to the production pump further comprises pumping the motor lubricant to the linear hydraulic pump through an external working fluid line. 
     
     
         20 . The method of  claim 18 , wherein the step of pumping the motor lubricant to the linear hydraulic pump further comprises pumping the motor lubricant to the linear hydraulic pump through an internal working fluid line.