Well Stimulation Pump Control and Method

• US 20170226998A1
• Filed: 02/04/2016
• Published: 08/10/2017
• Est. Priority Date: 02/04/2016
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Zhang, Yanchai, Dong, Zhaoxu, Hu, Xuefei
• Granted Patent: US 10,247,182 B2
• Time in Patent Office: Days
• CPC Class Codes: F04B 17/03 driven by electric motors
• CPC Class Codes: F04B 2205/02 Pressure in the inlet chamber
• CPC Class Codes: F04B 47/00 Pumps or pumping installations specially adapted for raising fluids from great depths, e.g. well pumps by using positive or negative pressurised fluid medium acting directly on the liquid to be pumped F04F1/00
• CPC Class Codes: F04B 49/065 and making use of computers
• CPC Class Codes: F04B 49/20 by changing the driving speed
• CPC Class Codes: F04B 49/22 by means of valves F04B49/03 takes precedence
• CPC Class Codes: F04B 51/00 Testing machines, pumps, or pumping installations

Abstract

A pumping system for use in a well stimulation application includes a pump controlled by a controller, the controller operating to monitor operation of the pump and determine when cavitation is present or imminent in the pump. When cavitation is present, the controller automatically adjusts an operating condition of the pump reduce pump speed or increase a fluid pressure at the pump inlet.

Claims

1. A pumping system for use in a well stimulation application, comprising:

a pump having an inlet and at least one pumping element, each pumping element including a piston reciprocally disposed in a bore, an inlet check valve in fluid communication with the inlet and an outlet check valve associated with a variable volume defined in a bore;

a pressure sensor disposed to measure a fluid pressure at a location between the inlet check valve and the inlet of the pump;

a drive mechanism for driving a reciprocal motion of the piston;

a speed sensor disposed to measure a speed of the pump at the drive mechanism; and

a controller associated with the pump and disposed to receive signals indicative of the fluid pressure and the speed of the pump;

wherein the controller is programmed to;

determine an operating point of the pump based on the fluid pressure and the speed of the pump;

compare the operating point of the pump with a cavitation map that is predefined;

determine whether cavitation is present in the at least one pumping element based on a result of the comparison between the operating point and the cavitation map; and

when cavitation is present, at times, adjust an operation of the drive mechanism to reduce a speed of the pump.

2. The pumping system of claim 1, wherein the cavitation map includes a two dimensional array of operating points with respect to the fluid pressure and the speed of the pump, and wherein a cavitation area is defined by a collection of operating points in the cavitation map at which cavitation occurs or is imminent.

3. The pumping system of claim 2, wherein the controller is further programmed to interpolate the operating point of the pump onto the cavitation map, and to determine whether the operating point of the pump falls within the cavitation area.

4. The pumping system of claim 1, wherein the drive mechanism includes a driver connected to an input drive shaft of the pump via a transmission device.

5. The pumping system of claim 4, wherein the controller adjusts the operation of the drive mechanism by commanding a change in a gear ratio of the transmission.

6. The pumping system of claim 4, wherein the driver includes an internal combustion engine connected to an electrical power generator, and an electric motor that is connected to the input drive shaft of the pump and wherein, during operation, the internal combustion engine operates the electrical power generator to produce electrical power, which electrical power is provided to operate the electric motor.

7. The pumping system of claim 6, wherein the controller adjusts the operation of the drive mechanism by commanding a change in a rotational speed of the electric motor.

8. The pumping system of claim 1, wherein the inlet of the pump is adapted to be connected to a source of stimulation fluid via a valve, the valve being responsive to commands from the controller for adjusting at least one of a flow rate and a pressure of stimulation fluid provided to the inlet of the pump.

9. The pumping system of claim 8, wherein the controller is further programmed to, at times when cavitation is present, adjust a position of the valve to increase the pressure of stimulation fluid provided to the inlet of the pump.

10. The pumping system of claim 8, wherein the source of stimulation fluid is a mixer device that is configured to provide a fluid in mixture with an aggregate as a slurry to the inlet of the pump, and wherein the mixer device is responsive to commands to adjust a composition of the slurry.

11. The pumping system of claim 10, wherein the controller is further programmed to provide an indication of a desired slurry composition when cavitation is present.

12. The pumping system of claim 1, wherein the controller is programmed to store in a database a plurality of predefined cavitation maps, and to select an appropriate cavitation map based on system operating parameters, the system operating parameters including physical characteristics of the stimulation fluid provided to the inlet of the pump and flow characteristics of piping associated with the pump.

13. The pumping system of claim 1, further including a second pump connected in parallel flow arrangement with the pump, wherein the controller is further programmed to adjust operation of the second pump when cavitation is present in the pump.

14. A method for operating a pump for use in a hydraulic fracturing system, comprising:

in a controller, selecting one appropriate cavitation map from a plurality of cavitation maps stored in the controller, the selecting being based on operating parameters of the hydraulic fracturing system;

using the controller, monitoring operation of the hydraulic fracturing system with regard to at least a pressure of stimulation fluid at an inlet of a pump, and a speed of the pump, to determine an operating condition of the pump;

in the controller, comparing the operating condition of the pump with the selected one appropriate cavitation map;

by use of the controller, determining whether cavitation is present or imminent in the pump based on a result of the comparison; and

when cavitation is present, using the controller to adjust the operating condition of the pump, in real time.

15. The method of claim 14, wherein adjusting the operating condition of the pump includes increasing a pressure of the stimulation fluid at the inlet of the pump.

16. The method of claim 14, wherein adjusting the operating condition of the pump includes reducing the speed of the pump.

17. The method of claim 14, wherein reducing the speed of the pump includes at least one of changing a gear ratio in a transmission device disposed between a power unit used to operate the pump and an input shaft of the pump, reducing a speed of an internal combustion engine used to operate the pump, and reducing an amount of electrical power provided to a motor operating the pump.

18. The method of claim 14, further comprising connecting the inlet of the pump to a source of stimulation fluid via a valve, the valve being responsive to commands from the controller for adjusting at least one of a flow rate and a pressure of stimulation fluid provided to the inlet of the pump, and adjusting a position of the valve to increase the pressure of stimulation fluid provided to the inlet of the pump.

19. The method of claim 18, wherein the source of stimulation fluid is a mixer device that is configured to provide a fluid in mixture with an aggregate as a slurry to the inlet of the pump, wherein the mixer device is responsive to commands to adjust a composition of the slurry, and wherein the controller is disposed to provide an indication of a desired slurry composition when cavitation is present.

20. The method of claim 14, wherein the system further includes a second pump connected in parallel flow arrangement with the pump, and wherein adjusting the operating condition of the pump is accomplished at least in part by adjust a corresponding operating condition of the second pump.