Motor controller for electrical submersible pumps

• US 5,015,151 A
• Filed: 05/14/1990
• Issued: 05/14/1991
• Est. Priority Date: 08/21/1989
• Status: Expired due to Term

• Current Assignee: Shell Oil Company (Shell Plc)
• Original Assignee: Shell Oil Company (Shell Plc)
• Inventors: Snyder, Dale R. Jr., Haws, Joe H.
• Primary Examiner(s): Smith, Leonard E.
• Assistant Examiner(s): Scheuermann, David W.
• Application Number:
  US07/523,296
• Time in Patent Office: 365 Days
• Field of Search: 417/12, 417/17, 417/18, 417/44, 417/45, 417/53
• US Class Current: 417/18
• CPC Class Codes: E21B 43/128 Adaptation of pump systems with down-hole electric drives
• CPC Class Codes: E21B 47/008 Monitoring of down-hole pump systems, e.g. for the detection of "pumped-off" conditions
• CPC Class Codes: F04B 47/06 having motor-pump units situated at great depth
• CPC Class Codes: F04B 49/065 and making use of computers
• CPC Class Codes: F04D 13/10 adapted for use in mining bore holes
• CPC Class Codes: F04D 15/0254 the condition being speed or load
• CPC Class Codes: F04D 9/001 Preventing vapour lock F04D9/041 takes precedence

Abstract

Differential motor load drops are employed to indicate gas lock or pump off of an electrical submersible pump.

Claims

1. A method for measuring differential pump fluid power output comprising:

(a) measuring pump motor power consumption at timed intervals;

(b) determining a recent pump motor power consumption from the measurements;

(c) determining a previous pump motor power consumption from the measurements;

(d) deriving the difference between steps (b) and (c), the difference being indicative of differential pump fluid power output; and

(e) shutting the pump down when said differential exceeds a predetermined amount for a predetermined length of time.

2. A method for detecting loss of pump fluid power output comprising:

(a) measuring pump motor power consumption at timed intervals;

(b) determining a recent pump motor power consumption from the measurements;

(c) determining a previous pump motor power consumption from the measurements;

(d) deriving the difference between steps (b) and (c), the difference being indicative of loss of pump fluid power output when said difference exceeds a predetermined quantity; and

(e) shutting the pump motor down when said difference is detected which exceeds a predetermined quantity for a predetermined length of time.

3. Apparatus for measuring differential pump fluid power output comprising:

(a) means for measuring pump motor power consumption at timed intervals;

(b) means for determing a recent pump motor power consumption from the measurements;

(c) means for determing a previous pump motor power consumption from the measurements;

(d) means for deriving the difference between steps (b) and (c), the difference being indicative of loss of differential pump fluid power output when said difference exceeds a predetermined quantity; and

(e) means for shutting the pump motor down when said difference exceeds said predetermined quantity.

5. The apparatus of claim 3 or 4 wherein the pump motor drive is selected from (1) an electric motor and (2) a hydraulic motor.

6. The apparatus of claim 3 or 4 wherein the pump is utilized with a motor drive selected from one of the following combinations:

(1) a centrifugal pump with an electric motor, (2) a centrifugal pump with an hydraulic motor, (3) a positive displacement pump with an electric motor drive, (4) a positive displacement pump with a hydraulic motor drive.

4. (Twice amended) Apparatus for detecting loss of pump fluid power output comprising:

(a) means for measuring pump motor power consumption at timed intervals;

(b) means for determining a recent pump motor power consumption from the measurements;

(c) means for determining a previous pump motor power consumption from the measurements;

(d) means for deriving the difference between steps (b) and (c), the difference being indicative of loss of pump fluid power output when said difference exceeds a predetermined quantity; and

(e) means for shutting the pump motor down when said loss of pump fluid power output is detected which exceeds a predetermined quantity for a predetermined length of time.

7. A method for detecting electrical submersible pump motor underload, comprising:

(a) measuring pump motor loads at timed intervals;

(b) determining a recent pump motor load from the measurements;

(c) determining a previous pump motor load from the measurements;

(d) deriving the difference between steps (b) and (c), the difference being indicative of pump motor underloaded when said difference exceeds a predetermined quantity; and

(e) shutting the pump motor down when said under-load is detected.

9. The method of claim 7 wherein said motor loads are monitored from apparent power utilized by said pump motor.

10. The method of claim 7 wherein said motor loads are monitored from actual power utilized by said pump motor.

11. The method of claim 7 wherein said motor loads are monitored from reactive power utilized by said pump motor.

12. The method of claim 7 wherein said motor loads are monitored from power factor utilized by said pump motor.

13. The method of claim 7 wherein said recent motor load is an average of measurements computed over a selected time interval.

14. The method of claim 7 wherein step (d) is based on a computation of the differential of motor load with respect to time.

15. The method of claim 7 wherein step (d) is based on integration of motor load with respect to time.

16. The method of claim 7 wherein step (d) is based on statistical analysis.

17. The method of claim 7 wherein said motor loads are monitored from current utilized by said pump motor.

18. The method of claim 17 wherein voltage accompanying said current is utilized to screen out corresponding current fluctuations which are the result of voltage spikes or sags and not pumpoff or gas locking.

19. The method of claim 7 wherein the most recent motor load measurement is used in step (b).

20. The method of claim 19 wherein said most recent motor load measurement is based on more than one measurement.

21. The method of claim 7 or 20 wherein said previous motor load is based on more than one measurement.

22. The method of claim 7 or 13 wherein said previous motor load is an average of measurements computed over a selected time interval.

8. A method for detecting electrical submersible pump motor underloaded, comprising:

(a) measuring pump motor loads at timed intervals;

(b) determining a recent pump motor load from the measurements;

(c) determining a previous pump motor load from the measurements;

(d) deriving the difference between steps (b) and (c), the difference being indicative of pump motor underload when said difference exceeds a predetermined quantity; and

(e) shutting the pump motor down when said underload is detected which exceeds a predetermined length of time.

23. A method for detecting electrical submersible pump motor underload, comprising:

(a) measuring motor current at timed intervals;

(b) determining the most recent motor current from the measurements;

(c) determining a moving average of the previous motor current from the measurements;

(d) derving the difference between steps (b) and (c), the difference being indicative of pump motor underload when said difference exceeds a predetermined quantity; and

(e) shutting the pump motor down when said difference exceeds one percent and wherein oil is being pumped in a non-gassy pumping condition.

24. A method for detecting electrical submersible pump motor underload, comprising:

(a) measuring motor current at timed intervals;

(b) determining the most recent motor current from the measurements;

(c) determining a moving average of the previous motor current from the measurements;

(d) deriving the difference between steps (b) and (c), the difference being indicative of pump motor underload when said difference exceeds a predetermined quantity; and

(e) shutting the pump motor down when said difference exceeds one percent for more than two seconds and wherein oil is being pumped in a gassy pumping condition.

25. An apparatus for detecting electrical submersible pump motor underload, comprising:

(a) means for measuring pump motor loads at timed intervals;

(b) means for determining a recent pump motor load from the measurements;

(c) means for determining a previous pump motor load from the measurements;

(d) means for deriving the difference between steps (b) and (c), the difference being indicative of pump motor underload when said difference exceeds a predetermined quantity; and

(e) means for shutting the pump motor down when said underload is detected.

27. The apparatus of claim 25 including means for monitoring said motor load from apparent power utilized by said pump motor.

28. The apparatus of claim 25 including means for monitoring said motor loads from actual power by said pump motor.

29. The apparatus of claim 25 including means for monitoring said motor loads from reactive power utilized by said pump motor.

30. The apparatus of claim 25 including means for monitoring said motor loads from a power factor indicated by said pump motor.

31. The apparatus of claim 25 including means for monitoring said motor loads from current utilized by said pump motor.

33. The apparatus of claims 25 or 32 applied as a controller subassembly wired in series with a motor controller, said controller subassembly being functional to augment or replace underload functions of said motor controller.

34. The apparatus of claims 25 or 32 applied as an integrated motor controller package functional to replace underload functions of a motor controller with gas lock/pump off controller functions.

35. The apparatus of claims 25 or 32 applied as an integrated intelligent remote terminal unit functional to excercise motor control functions to include pump off/gas lock control and have capabilities of monitoring electrical submersible pump operation parameters, storing operation data and communication with a central computer.

26. An apparatus for detecting electrical submersible pump motor underload, comprising:

(a) means for measuring pump motor loads at timed intervals;

(b) means for determining a recent pump motor load from the measurements;

(c) means for determining a previous pump motor load from the measurements;

(d) means for deriving the difference between steps (b) and (c), the difference being indicative of pump motor underload when said difference exceeds a predetermined quantity; and

(e) means for shutting the pump motor down when said underload is detected which exceeds a predetermined length of time.

32. An apparatus for detecting electrical submersible pump motor underload, comprising:

(a) means for measuring motor current at timed intervals;

(b) means for determining the most recent motor current from the measurements;

(c) means for determining a moving average of the previous motor current from the measurements;

(d) means for deriving the difference between steps (b) and (c), the difference being indicative of pump motor underload when said difference exceeds a predetermined quantity; and

(e) means for shutting the pump motor down when said difference exceeds one percent and wherein oil is being pumped in a non-gassy pumping condition.

36. An apparatus for detecting electrical submersible pump motor underload, comprising:

(a) means for measuring motor current at timed intervals;

(b) means for determining the most recent motor current from the measurements;

(c) means for determining a moving average of the previous motor current from the measurements;

(d) means for deriving the difference between steps (b) and (c), the difference being indicative of pump motor underload when said difference exceeds a predetermined quantity; and

(e) means for shutting the pump motor down when said difference exceeds one percent for more than two seconds and wherein oil is being pumped in a gassy pumping condition.