Submersible pumping systems and methods for deep well applications

Abstract

Submersible pumping systems, devices and methods for extracting liquids in deep well applications are disclosed. In the various embodiments, a submersible pumping system includes a power supply and a power converter coupled to the power supply. A subsurface unit may be coupled to the power converter and positioned in the well. The subsurface unit may include a subsurface controller, a motor and a pump portion operably coupled to the subsurface controller. The pump portion may further include a front shroud having an inlet, and a back shroud sealably coupled to the front shroud to define a volume. An orifice fluidly communicates with the volume and an annular fluid discharge space disposed about the subsurface unit. An impeller operably coupled to the motor and positioned within the volume may transport a liquid from the inlet to the annular fluid discharge space.

1 . A submersible pumping system for a well, comprising:
 a power supply;   a power converter coupled to the power supply; and   a subsurface unit coupled to the power converter and configured to be positioned in the well remote from the power supply and the power converter, wherein the subsurface unit includes a subsurface controller, and a motor and a pump portion operably coupled to the subsurface controller, the pump portion further comprising:   a front shroud having an inlet;   a back shroud sealably coupled to the front shroud to define a volume there between;   an orifice that fluidly communicates with the volume and an annular fluid discharge space at least partially disposed about the subsurface unit; and   an impeller operably coupled to the motor and positioned within the volume to transport a liquid from the inlet to the annular fluid discharge space.   
     
     
         2 . The system of  claim 1 , wherein the front shroud includes an axially disposed conical inner portion having a taper angle that ranges between approximately 45 degrees and approximately 60 degrees. 
     
     
         3 . The system of  claim 1 , wherein the front shroud comprises a strainer fluidly coupled to the inlet that is configured to restrict the entry of solid material into the volume. 
     
     
         4 . The system of  claim 1 , wherein the orifice comprises a constant diameter portion and a tapered portion coupled to the constant diameter portion, the tapered portion having an included angle that ranges between approximately five degrees, and approximately 50 degrees. 
     
     
         5 . The system of  claim 4 , wherein the constant diameter portion comprises a diameter that ranges between approximately 0.030 inches, and approximately 0.120 inches. 
     
     
         6 . The system of  claim 1 , wherein the impeller comprises a planar and circular disk that supports a plurality of outwardly extending vanes, and a centrally disposed impeller hub configured to be coupled to the motor. 
     
     
         7 . The system of  claim 6 , wherein the disk comprises a plurality of apertures extending through the disk and positioned between the outwardly extending vanes. 
     
     
         8 . The system of  claim 6 , wherein the outwardly extending vanes are spaced apart from the front shroud by a clearance distance that ranges between approximately 0.005 inch and approximately 0.040 inch. 
     
     
         9 . The system of  claim 6 , wherein the outwardly extending vanes are inclined at an angle that ranges between approximately 45 degrees and approximately 60 degrees. 
     
     
         10 . The system of  claim 6 , wherein the impeller hub is configured to fixedly retain a shaft extending from the motor using an interference fit. 
     
     
         11 . The system of  claim 1 , wherein the motor comprises a polyphase, brushless and sensor less DC motor. 
     
     
         12 . A submersible pumping system for a well, comprising:
 a power supply;   a power converter coupled to the power supply; and   a subsurface unit coupled to the power converter and configured to be positioned in the well remote from the power supply and the power converter, wherein the subsurface unit includes a pump portion and a motor operably coupled to the pump portion, and a subsurface controller, the subsurface controller further comprising:   a power compensation circuit operable to receive electrical power from the power converter configured to reduce at least one of a reactance introduced by the motor and reactive and resistive effects introduced by electrical leads coupling the power converter to the subsurface unit;   a motor controller coupled to the power compensation circuit that is configured to convert electrical power received from the power compensation circuit to polyphase electrical power that is communicated to the motor; and   a motor speed controller configured to control a rotational speed of the motor when the polyphase electrical power is first applied to the motor.   
     
     
         13 . The system of  claim 12 , wherein the power supply comprises one of an alternating current (AC) source and a direct current (DC) source. 
     
     
         14 . The system of  claim 13 , wherein the DC source comprises one of a storage battery, one or more photovoltaic panels, and a fuel cell device. 
     
     
         15 . The system of  claim 13 , wherein the power converter comprises a DC-to DC converter configured to receive a DC voltage at a first voltage level, and convert the DC voltage to a second voltage level. 
     
     
         16 . The system of  claim 15 , wherein the DC-to-DC converter comprises one of a buck-boost converter, a boost converter and a buck converter. 
     
     
         17 . The system of  claim 15 , wherein the DC-to-DC converter is coupled to an AC-to-DC converter that receives an AC voltage from the power supply, and converts the AC voltage to a DC voltage. 
     
     
         18 . The system of  claim 12 , wherein the power compensation circuit comprises one or more capacitors operably coupled to the power converter and the motor controller. 
     
     
         19 . The system of  claim 12 , wherein the motor controller comprises at least one inverter circuit configured to receive a DC voltage, and to convert the DC voltage to an AC voltage. 
     
     
         20 . The system of  claim 12 , wherein the motor controller comprises a speed sensing circuit that is operable to sense a back electromotive force from the motor and to regulate a speed of the motor based upon the sensed electromotive force. 
     
     
         21 . The system of  claim 12 , wherein the motor speed controller is configured to provide a motor speed distribution that is implemented during a time period that extends from a motor start value to a maximum speed value. 
     
     
         22 . The system of  claim 21 , wherein the time period is approximately one to three seconds. 
     
     
         23 . The system of  claim 21 , wherein the motor speed distribution extends linearly during the time period. 
     
     
         24 . The system of  claim 21 , wherein the motor speed distribution comprises one of a second-degree speed distribution and a third-degree speed distribution. 
     
     
         25 . A submersible pumping system for a well, comprising:
 a power supply;   a feedback system coupled to the power supply; and   a subsurface unit coupled to the feedback system and configured to be positioned in the well remote from the power supply and the feedback system, wherein the subsurface unit includes at least a pump portion and a motor operably coupled to the pump portion, the pump portion being operable to transport a volume of a liquid from the well to a flow meter, the feedback system further comprising:   a control mode unit configured to implement a predetermined control mode;   a power converter coupled to the control mode unit that is configured to receive electrical power from the power supply, and to controllably provide electrical power to the subsurface unit based upon an out\put from the control mode unit; and   a comparator that receives a feedback signal from the flow meter that provides an error signal to the control mode unit based upon a comparison of the feedback signal and a desired flow value.   
     
     
         26 . The system of  claim 25 , wherein the control mode unit is configured to implement one of a proportional (P) control mode, a derivative (D) control mode, a proportional-derivative (P-D) control mode, an integral (I) control mode, a proportional-integral (P-I) control mode, and a proportional-integral-derivative (P-I-D) control mode. 
     
     
         27 . The system of  claim 25 , wherein the power converter comprises a DC-to DC converter configured to receive a DC voltage at a first voltage level, and convert the DC voltage to a second voltage level. 
     
     
         28 . The system of  claim 27 , wherein the DC-to-DC converter comprises one of a buck-boost converter, a boost converter and a buck converter. 
     
     
         29 . The system of  claim 25 , wherein the DC-to-DC converter is coupled to an AC-to-DC converter that receives an AC voltage from the power supply, and converts the AC voltage to a DC voltage. 
     
     
         30 . The system of  claim 29 , wherein the AC-to-DC converter comprises a rectifier circuit. 
     
     
         31 . A method of removing a liquid from a well, comprising:
 positioning a subsurface unit into a well, the subsurface unit including at least a pump portion coupled to a motor configured to impart a rotational motion to the pump portion;   coupling the subsurface unit to a power supply and a power converter configured to controllably provide electrical power to the subsurface unit; and   starting the motor using a selected motor speed distribution.   
     
     
         32 . The method of  claim 31 , wherein starting the motor using a selected motor speed distribution comprises implementing the motor speed distribution over a time period that ranges between approximately one to three seconds. 
     
     
         33 . The method of  claim 31 , wherein starting the motor using a selected motor speed distribution comprises a linear motor speed distribution. 
     
     
         34 . The method of  claim 31 , wherein starting the motor using a selected motor speed distribution comprises a parabolic motor speed distribution. 
     
     
         35 . The method of  claim 31 , wherein starting the motor using a selected motor speed distribution comprises a motor speed distribution conforming to a third-order polynomial. 
     
     
         36 . The method of  claim 31 , further comprising:
 setting a desired speed for steady-state motor operation;   detecting a variation in the steady-state motor operation by sensing a back electromotive force from the motor; and   correcting at least one of a voltage and a current delivered to the motor to return the motor to the desired speed.   
     
     
         37 . The method of  claim 36 , wherein setting a desired speed for steady-state motor operation comprises providing a control input to the power converter. 
     
     
         38 . A method of removing a liquid from a well, comprising:
 positioning a subsurface unit into a well, the subsurface unit including at least a pump portion and a motor coupled to the pump portion, the subsurface unit being configured to transport a liquid from the well to a surface location;   coupling the subsurface unit to a power supply and a feedback system configured to controllably provide electrical power to the subsurface unit;   selecting a desired flow rate to be delivered by the subsurface unit;   setting a speed for the motor that delivers the desired flow rate;   measuring a delivered flow rate; and   if the delivered flow rate differs from the desired flow rate, then correcting the speed to attain the desired flow rate.