Variable Rate Pumping System

Abstract

A pumping system comprising a motor, wherein the motor has an operating speed, a pump coupled to the motor, wherein the pump has a volumetric displacement, a fluid end coupled to the pump, wherein the fluid end is operable to draw fluid from an input and provide fluid to an output, and a control system operable to regulate the motor and the pump in order to provide fluid to the output at a selected pressure and flow rate within a continuous range of pressures and flow rates between the peak horsepower output and peak torque output of the motor.

1 . A method comprising:
 operating a pumping system to provide a fluid at a pressure and a flow rate within a continuous range of pressures and flow rates between a peak horsepower and a peak torque of the pumping system;   monitoring the pressure and the flow rate of the fluid provided by the pumping system;   controlling the pumping system to provide non-discrete variations in the pressure and the flow rate of the fluid; and   pumping the fluid into a subterranean wellbore.   
   
   
       2 . The method of  claim 1 , wherein the pumping system does not comprise a transmission. 
   
   
       3 . The method of  claim 2 , wherein the pumping system comprises a pump and a motor, wherein changes in the pressure and the flow rate are controlled by varying a speed of a motor. 
   
   
       4 . The method of  claim 3 , wherein a stroke of the pump is varied by axial translation of a rotating pump shaft. 
   
   
       5 . The method of  claim 2 , wherein the pumping system comprises a pump and a motor, and wherein the pressure and the flow rate are controlled by varying a displacement of the pump. 
   
   
       6 . The method of  claim 5 , wherein a ratio of a rotational speed of the motor to a rotational speed of the pump is fixed. 
   
   
       7 . The method of  claim 5 , wherein the displacement of the pump can be adjusted by varying a stroke of the pump. 
   
   
       8 . A method comprising:
 controlling a plurality of operating parameters of a pump to provide a fluid output at any combination of pressure and flow rate within a range defined by a peak hydraulic horsepower, a peak torque, a maximum pressure, and a maximum flow rate of the pump;   monitoring the pressure and the flow rate of the fluid output; and   adjusting at least one of the operating parameters of the pump to provide a desired pressure and flow rate of the fluid output,   wherein the fluid is a wellbore servicing fluid.   
   
   
       9 . The method of  claim 8 , wherein the pump is not coupled to a transmission. 
   
   
       10 . The method of  claim 8 , wherein the adjusted operating parameter comprises a speed of the pump. 
   
   
       11 . The method of  claim 10 , wherein the speed of the pump is adjusted by adjusting the speed of a motor operating the pump. 
   
   
       12 . The method of  claim 11 , wherein the speed of the pump is related to the speed of the motor by a fixed ratio. 
   
   
       13 . The method of  claim 8 , wherein the adjusted operating parameter comprises a displacement of the pump. 
   
   
       14 . The method of  claim 13 , wherein the displacement of the pump is determined by the axial position of a rotating shaft. 
   
   
       15 . The method of  claim 14 , wherein the axial position of the rotating shaft is regulated by a displacement controller comprising a coupling engaged with the rotating shaft and a hydraulic cylinder operable to engage the coupling so as to axially translate the rotating shaft. 
   
   
       16 . A method comprising:
 operating a pumping system comprising a pump and a motor to provide a fluid at a pressure and a flow rate within a continuous range of pressures and flow rates between a peak horsepower and a peak torque of the pumping system, wherein the pumping system does not comprise a transmission; and   pumping the fluid into a subterranean wellbore.   
   
   
       17 . The method of  claim 16 , wherein the pressure and the flow rate are determined by operating parameters consisting essentially of: a displacement of the pump and a speed of the motor. 
   
   
       18 . The method of  claim 17 , wherein the displacement of the pump is determined by the axial position of a rotating shaft. 
   
   
       19 . The method of  claim 18 , wherein the axial position of the rotating shaft is regulated by a displacement controller comprising a coupling engaged with the rotating shaft and a hydraulic cylinder operable to engage the coupling so as to axially translate the rotating shaft. 
   
   
       20 . The method of  claim 16 , wherein the fluid comprises fracturing fluid, drilling mud, barite, cement, liquid CO 2 , or combinations thereof.