Electric motor and rod-driven rotary gear pumps

Abstract

A downhole pumping apparatus comprising a positive displacement rotary gear pump (RGP), driven by a rotating rod string or a submersible electric motor.

1 . A method for producing a fluid from a wellbore toward a ground surface, the method comprising the steps of:
 (a) deploying into the wellbore a pump system comprising:
 (i) a housing enclosing a rotary gear pump (RGP) with an input shaft; 
 (ii) a drive shaft coupled to the input shaft and comprising either: an output shaft of a submersible electric motor; or a rotating rod string; and wherein the drive shaft is aligned with the axial centerline of the housing and the RGP input shaft is offset from the axial centerline of the housing; and 
   (b) rotating the drive shaft to drive the RGP to pressurize fluid up the wellbore toward the ground surface.   
     
     
         2 . The method of  claim 1  wherein the drive shaft comprises the output shaft of the electric submersible motor, and the drive shaft is rotated by the electric submersible motor. 
     
     
         3 . The method of  claim 2  wherein the RGP input shaft is coupled to the motor output shaft by a gear box comprising a gear box input shaft aligned with the axial centerline of the housing and a gear box output offset from the axial centerline of the housing and aligned with the RGP input shaft. 
     
     
         4 . The method of  claim 2  wherein the RGP input shaft is coupled to the motor output shaft by a flex coupling. 
     
     
         5 . The method of  claim 4  wherein the flex coupling comprises:
 (a) a flex coupling input shaft aligned with the axial centerline of the housing; 
 (b) a flex coupling output shaft aligned with the RGP input shaft; 
 (c) a flex coupling connecting shaft comprising first and second enlarged ends; and 
 (d) a flex coupling first housing rigidly connected to the flex coupling input shaft, and rotationally connected to the first enlarged end; and a flex coupling second housing rigidly connected to the flex coupling output shaft, and rotationally connected to the second enlarged end. 
 
     
     
         6 . The method of  claim 5  wherein the flex coupling first housing and the first enlarged end define intermeshing splines that permit a limited amount of lateral displacement of the first enlarged end relative to the flex coupling first housing. 
     
     
         7 . The method of  claim 6  wherein the flex coupling second housing and the second enlarged end define intermeshing splines that permit a limited amount lateral displacement of the second enlarged end relative to the flex coupling second housing. 
     
     
         8 . The method of  claim 1  wherein the drive shaft comprises the rotating rod string, and the drive shaft is rotated by a prime mover at the ground surface. 
     
     
         9 . The method of  claim 8  wherein the RGP input shaft is removably coupled to the rotating rod string by a coupling defining a first splined connection with a bottom end of the rotating rod string, and a second splined connection with the RGP input shaft. 
     
     
         10 . The method of  claim 8  wherein the RGP input shaft is coupled to the rotating rod string by a gear box comprising a gear box input shaft aligned with the axial centerline of the housing and a gear box output offset from the axial centerline of the housing and aligned with the RGP input shaft. 
     
     
         11 . A pump system deployed in a wellbore for producing a fluid from the wellbore toward a ground surface, the pump system comprising:
 (a) a housing enclosing a rotary gear pump (RGP) with an input shaft;   (b) a drive shaft coupled to the input shaft and comprising either: an output shaft of a submersible electric motor; or a rotating rod string; wherein the drive shaft is aligned with the axial centerline of the housing and the RGP input shaft is offset from the axial centerline of the housing.   
     
     
         12 . The pump system of  claim 11  wherein the drive shaft comprises the output shaft of the electric submersible motor. 
     
     
         13 . The pump system of  claim 12  wherein the RGP input shaft is coupled to the motor output shaft by a gear box comprising a gear box input shaft aligned with the axial centerline of the housing and a gear box output offset from the axial centerline of the housing and aligned with the RGP input shaft. 
     
     
         14 . The pump system of  claim 12  wherein the RGP input shaft is coupled to the motor output shaft by a flex coupling. 
     
     
         15 . The pump system of  claim 14  wherein the flex coupling comprises:
 (a) a flex coupling input shaft aligned with the axial centerline of the housing; 
 (b) a flex coupling output shaft aligned with the RGP input shaft; 
 (c) a flex coupling connecting shaft comprising first and second enlarged ends; and 
 (d) a flex coupling first housing rigidly connected to the flex coupling input shaft, and rotationally connected to the first enlarged end; and a flex coupling second housing rigidly connected to the flex coupling output shaft, and rotationally connected to the second enlarged end. 
 
     
     
         16 . The pump system of  claim 15  wherein the flex coupling first housing and the first enlarged end define intermeshing splines that permit a limited amount of lateral displacement of the first enlarged end relative to the flex coupling first housing. 
     
     
         17 . The pump system of  claim 16  wherein the flex coupling second housing and the second enlarged end define intermeshing splines that permit a limited amount lateral displacement of the second enlarged end relative to the flex coupling second housing. 
     
     
         18 . The pump system of  claim 11  wherein the drive shaft comprises the rotating rod string. 
     
     
         19 . The pump system of  claim 18  wherein the RGP input shaft is removably coupled to the rotating rod string by a coupling defining a first splined connection with a bottom end of the rotating rod string, and a second splined connection with the RGP input shaft. 
     
     
         20 . The pump system of  claim 18  wherein the RGP input shaft is coupled to the rotating rod string by a gear box comprising a gear box input shaft aligned with the axial centerline of the housing and a gear box output offset from the axial centerline of the housing and aligned with the RGP input shaft.