Pump control device, oil well with device and method

• US 20110097214A1
• Filed: 10/26/2009
• Published: 04/28/2011
• Est. Priority Date: 10/26/2009
• Status: Active Grant

• Current Assignee: Harold Wells Associates, Inc.
• Original Assignee: Harold Wells Associates, Inc.
• Inventors: Lamascus, Craig, Wentworth, Lloyd
• Granted Patent: US 9,234,517 B2
• Time in Patent Office: Days
• US Class Current: 417/44.1
• CPC Class Codes: F04B 47/02 the driving mechanisms being situated at ground level F04B47/12 takes precedence
• CPC Class Codes: F04B 49/02 Stopping, starting, unloading or idling control
• CPC Class Codes: F04B 49/06 Control using electricity regulating by means of floats actuating electric switches F04B49/04
• CPC Class Codes: F04B 49/103 Responsive to speed
• CPC Class Codes: F04B 49/12 by varying the length of stroke of the working members

Abstract

A method of operating an oil well comprises applying through a variable frequency drive AC electrical energy from a power grid to an AC electric motor to operate a drive mechanism of an oil well pump. The motor speed is regulated in a manner to optimize oil production and maximize the operational life of the drive mechanism, decreasing motor speed by transferring the electrical energy to the power grid and increasing motor speed by transferring the electrical energy from the power grid to the motor. The drive mechanism has a predetermined stroke cycle and, over the course of each stroke cycle, the motor is operated at different regulated speeds initiated when the drive mechanism is at a predetermined position in each stroke cycle.

Claims

1. An oil well including

a pump having a drive mechanism operably connected to an AC electric motor powered by AC electrical energy from a power grid, and

a variable frequency AC drive that controls the AC electrical energy in the motor to decrease motor speed by transferring the electrical energy to the power grid and to increase motor speed by transferring the electrical energy from the power grid to the motor,

said variable frequency AC drive regulating the motor speed in a manner to optimize oil production and maximize the operational life of the drive mechanism.

2. In an oil well where a pump driven by an AC electric motor moves a rod of the pump through a predetermined stroke cycle and a signal generator provides a signal when the rod is at a predetermined position in the stroke cycle of the rod,

an improvement wherein AC electricity from a power grid is transferred to the motor under the control of a variable frequency drive that regulates the instantaneous velocity of the motor based on a calculated position of the rod over the course of each stroke cycle with the calculation initiated when the rod is at said predetermined position as indicated by said signal, decreasing motor speed by transferring electrical energy to the power grid and increasing motor speed by transferring electrical energy from the power grid to the motor.

3. The oil well of claim 2 where the instantaneous velocity is regulated over the course of each stroke cycle, increasing and decreasing the motor speed to maximize oil production and minimize tension in the rod on the upstroke and maximize tension in the rod on the downstroke.

4. The oil well of claim 2 where the variable frequency drive includes a microprocessor that calculates rod position throughout the entire stroke cycle according to the equation

X=K∫

₀^ToVdt

where

X=rod position based on percent of cycle (0 to 100%)

V=motor speed (instantaneous revolutions per minute (rpm)

K=scaling constant,

T_o=time at which “

end of stroke”

signal is received.

5. An oil well comprising

a pumping system including a pump that has a rod extending below ground level into an oil well formation,

an AC electrical motor that moves the rod through a stroke cycle having an upstroke and a downstroke, said motor being operably connected to the rod through a mechanism that operably connects the motor to the rod and rotates through a known number of revolutions with each stroke cycle,

a first sensor that provides an end of stroke signal each time the rod is at an end of the downstroke during each stroke cycle,

an AC drive that provides electrical energy from an AC power grid to the motor, said AC drive being capable of decreasing motor speed by transferring electrical energy to the power grid and increasing motor speed by transferring electrical energy from the power grid to the motor,

a well manager control unit that controls the operation of the oil well in response to conditions of the oil well and provides for each stroke cycle a speed signal corresponding to an optimum average motor speed to maximize oil production under the then present well conditions,

said AC drive including a microprocessor with an input at which the speed signal is received and an input at which the end of stroke signal is received,

said microprocessor being programmed

to vary the instantaneous velocity of the motor based on (i) the speed signal and (ii) a calculated position of the rod over the course of each stroke cycle, increasing and decreasing the motor speed to maximize oil production and minimize tension in the rod on the upstroke and maximize tension in the rod on the downstroke, said calculation of rod position being initiated each time said end of stroke signal is received,

to set the motor at a predetermined minimum speed whenever the calculated rod position indicates a rotation greater than said known number of revolutions and the end of stroke signal has not been received, and

after setting the motor speed at said predetermined minimum speed and once again receiving the end of stroke signal, to vary the instantaneous velocity of the motor based on (i) the speed signal and (ii) a calculated rod position.

6. The oil well of claim 5 including a second sensor that monitors tension in the rod and provides a tension signal corresponding to the measured tension, and the microprocessor has an input that receives the tension signal and is programmed to take into account the measured tension.

7. An oil well having a pumping system comprising

a pump that has a rod extending below ground level into the oil well,

an AC electrical motor operably connected to the rod to drive the rod through a predetermined stroke cycle,

a sensor that provides a signal each time the rod is at a predetermined position during each stroke cycle, and

a pump control device that regulates the frequency and voltage of AC electrical power from an AC power grid that is transferred to the AC electrical motor,

said pump control device including a microprocessor that controls the speed of the motor, said microprocessor programmed to drive the electrical motor over the course of each stroke cycle at different speeds as a function of calculated the rod position, decreasing the motor speed by transferring electrical energy to the power grid and increasing the motor speed by transferring electrical energy from the power grid to the motor.

8. A control device for an AC electric motor adapted to be operably connected to a pump for an oil well to vary the speed of the motor as the pump moves through an entire stroke cycle, said control device including

a variable frequency drive that during each stroke cycle converts AC current at a standard frequency and voltage from an AC power grid to a variable AC current and applies the variable AC current to the motor to decrease motor speed by transferring electrical energy to the power grid and to increase motor speed by transferring electrical energy from the power grid to the motor,

said variable frequency drive having a microprocessor including an input to be placed in communication with a well manager unit that provides an average motor speed signal that indicates increasing and decreasing the speed of the motor based on conditions of the oil well and an input to be placed in communication with a sensor that provides a signal indicating a predetermined pump position that is the same for each stroke cycle,

said microprocessor programmed to provide at an output of the microprocessor a regulating signal for the variable AC current that modulates frequency and voltage of the variable AC current as a function of the motor speed signal and a calculated pump position over the course of each stroke cycle initiated each time the signal is received.

9. The pump control device of claim 8 where the position is calculated according to the equation

X=K∫

₀^ToVdt

where

X=position based on percent of cycle (0 to 100%)

V=motor speed (instantaneous revolutions per minute (rpm)

K=scaling constant,

T_o=time at which the signal is received.

10. The pump control device of claim 8 where the microprocessor is programmed to operate the motor at a predetermined minimum speed whenever said signal is not received during any stroke cycle.

11. The pump control device of claim 8 including a circuit that controls the waveform of the input AC current to reduce low order harmonic current drawn from the power grid.

12. The pump control device of claim 8 including IGBT transistors that are switched on and off in such a manner that results in current flow and voltage that is substantially sinusoidal.

13. The pump control device of claim 8 including an inductive and capacitive filter that reduces harmonic voltage distortion caused by switching of a converter circuit directly to the input AC current.

14. A pump control device that regulates the frequency and voltage of electrical energy from an AC power grid transferred to an AC electrical motor that drives a rod of an oil well pump having a predetermined stroke cycle, said device comprising

means during each stroke cycle for transferring electrical energy in both directions between the electrical motor and the AC power grid and for providing a controlled variable AC current for driving the electrical motor over the course of each stroke cycle at different speeds at least in part as a function of calculated the rod position, and

means for initiating operation of motor over the course of each stroke cycle at said different speeds in response to a signal generated each time the rod is at a predetermined rod position in each stroke cycle,

said motor speed being decreased by transferring electrical energy to the power grid and being increased by transferring electrical energy from the power grid to the motor and being operated at a predetermined minimum speed whenever said the signal is not received during in any stroke cycle.

15. A method of operating an oil well comprising the steps of

applying through a variable frequency drive AC electrical energy from a power grid to an AC electric motor operating a drive mechanism of a pump that pumps oil from the well, and

regulating the motor speed in a manner to optimize oil production and maximize the operational life of the drive mechanism, decreasing motor speed by transferring the electrical energy to the power grid and increasing motor speed by transferring the electrical energy from the power grid to the motor.

16. The method of claim 15 where the drive mechanism has a predetermined stroke cycle and, over the course of each stroke cycle, the motor is operated at different regulated speeds initiated when the drive mechanism is at a predetermined position in each stroke cycle.