Method for pumping fluids

Abstract

The production rate, useful life and operating efficiency of electric submergible pumping systems (ESP) is improved by operating the system so that the motor is cooled by two passes of production. The two passes of production fluid are achieved by employing a shroud with the inlet at the opposite end of the production fluid intake or by installing the motor below the perforations that allow production fluids to enter a well. The motor is designed with an internal conduit through which the production fluids are pumped. Production fluids remove waste heat from the motor by passing in fluid contact with the exterior of the motor and again by passing through the internal conduit of the motor. The improved cooling permits the motor to be operated at a lower temperature improving life and efficiency, and/or to be operated at higher power at a similar temperature. Additionally, oversized and excess equipment is not required, further improving performance and economics for the user. In another aspect, the invention is a method of pumping fluids using a motor having vortex generators on its exterior surfaces or on the interior surfaces of a surrounding shroud, and a method for determining optimum well operating conditions.

What is claimed is:  
     
         1 . A method of pumping a fluid with a submergible pumping system including a pump and an electrical motor, wherein 
 (a) the electrical motor has an internal conduit and said pumping system is adapted to pump said fluid through said internal conduit, and    (b) the pumping system is submerged in said fluid such that production fluids entering the pumping system pass in fluid contact with exterior portions of the electrical motor and remove heat therefrom before entering the pumping system, and said liquid production fluids then pass through the internal conduit of the electrical motor as the fluid is pumped, and remove additional heat from the motor.    
     
     
         2 . A method for producing fluids from a well having a casing that contains perforations through which production fluids enter the well, comprising 
 (a) positioning an electrical submergible pumping system including an electric motor within said casing such that the electric motor is at or below or downstream of at least some of said perforations, and    (b) pumping production fluids from the well with said pumping system,    wherein 
 (1) the pumping system includes a pump, an electrical motor having an internal conduit and production fluid intakes located below said electrical motor, said pumping system being adapted to pump said production fluids through said internal conduit of the electrical motor,  
 (2) production fluids entering the well through at least some of the perforations in the casing pass in fluid contact with exterior portions of the electrical motor and remove heat therefrom before entering the production fluid intakes, and  
 (3) production fluids pass through the internal conduit of the electrical motor as the fluid travels to the wellhead, and remove additional heat from the motor.  
   
     
     
         3 . The method of  claim 2  wherein the production fluids pass through the internal conduit of the electrical motor under conditions of turbulent flow.  
     
     
         4 . The method of  claim 3  wherein the internal conduit takes the form of a hollow drive shaft.  
     
     
         5 . The method of  claim 4  wherein the electrical motor is located between the wellhead and the pump.  
     
     
         6 . The method of  claim 5  wherein production fluids entering the well through the perforations in the casing travel downward in fluid contact past exterior portions of the electrical motor to an intake, and the liquid production fluids are subsequently pumped upwardly through the internal conduit of the electrical motor and then to the wellhead.  
     
     
         7 . The method of  claim 6 , wherein the flow of production fluid through the internal conduit is characterized by a Reynolds number of at least 2300.  
     
     
         8 . The method of  claim 7 , wherein the motor contains a motor fluid at a positive pressure to the exterior of the motor, and has seals which allow motor fluid to leak into the production fluid.  
     
     
         9 . The method of  claim 7 , wherein conditions are selected such that heat transfer from at least one of the internal conduit and the exterior surfaces of the motor to the production fluid is characterized by a Nusselt number of at least 10.  
     
     
         10 . The method of  claim 7  wherein the internal conduit is the drive shaft of the motor, and conditions are selected so as to generate a Brinkmann number of less than 2.  
     
     
         11 . The method of  claim 7  wherein the internal conduit is the drive shaft of the motor, and conditions are selected so as to generate a Rossby number of more than 0.5.  
     
     
         12 . The method of  claim 4  wherein the pump is located between the wellhead and the electric motor.  
     
     
         13 . The method of  claim 4  wherein electrical submergible pumping system contains two pumps, one of which is located above the electric motor and one of which is located below the electric motor.  
     
     
         14 . A method of pumping fluids with a submergible pumping system including a pump and an electrical motor, wherein the pumping system is submerged in production fluids such that said fluids flow across vortex generators adapted to impart streamwise vorticity to the production fluids as the pass in fluid contact with the exterior portions of the electrical motor.  
     
     
         15 . The method of  claim 14  wherein the vortex generators are attached to the exterior portions of the electric motor.  
     
     
         16 . The method of  claim 14  wherein the vortex generators are attached to the interior surface of a motor shroud.