Method and apparatus for detecting torsional vibration with a downhole pressure sensor

• US 20040206170A1
• Filed: 04/15/2003
• Published: 10/21/2004
• Est. Priority Date: 04/15/2003
• Status: Active Grant

• Current Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Original Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Inventors: Chen, Chen-Kang David, Beene, Paul D.
• Granted Patent: US 7,082,821 B2
• Time in Patent Office: Days
• US Class Current: 73/152.49
• CPC Class Codes: E21B 44/00 Automatic control systems specially adapted for drilling operations, i.e. self-operating systems which function to carry out or modify a drilling operation without intervention of a human operator, e.g. computer-controlled drilling systems; Systems specially adapted for monitoring a plurality of drilling variables or conditions

Abstract

A method and apparatus for detecting torsional vibration, or stick-slip, in a drill string while drilling is described. The method comprises sampling a downhole pressure sensor and using embedded filter schemes and algorithms to determine, based on the pressure samples, whether torsional vibration is occurring in the drill string. The method may also include sending a warning signal to the surface of the well. The apparatus comprises a downhole assembly having a downhole receiver and a master controller. The downhole receiver comprises a pressure sensor, filter schemes, and algorithms for detecting torsional vibration. The downhole assembly may also include a downhole transmitter for sending a warning signal to the surface of the well.

Claims

1. A method of detecting torsional vibration in a drillstring while conducting a drilling operation in a subterranean well, the method comprising:

sampling a downhole pressure sensor to obtain a data set; and

determining whether the data set indicates torsional vibration in the drillstring.

2. The method of claim 1 further comprising sending a warning signal to the surface of the well if the data set indicates torsional vibration.

3. The method of claim 2 further comprising changing at least one drilling parameter of the drilling operation in response to the warning signal.

4. The method of claim 2 further comprising changing a downlink signal frequency in response to the warning signal.

5. The method of claim 2 further comprising removing a portion of the data set that indicates torsional vibration.

6. A method of detecting torsional vibration in a drillstring while conducting a drilling operation in a subterranean well, the drillstring being part of a drilling assembly having a mud pulse telemetry system capable of sending uplink or downlink signals, the method comprising:

sampling a downhole pressure sensor to obtain a first data set;

analyzing the first data set; and

determining whether the data set indicates torsional vibration in the drillstring.

7. The method of claim 6 wherein the sampling step occurs at a frequency of at least 1 Hertz.

8. The method of claim 6 wherein the sampling step occurs within a bore of the drillstring.

9. The method of claim 6 wherein the sampling step occurs within an annulus between the drillstring and the subterranean well.

10. The method of claim 6 wherein the analyzing step includes sub-steps, the sub-steps comprising:

applying a first filter to the first data set to obtain a second data set;

applying a second filter to the second data set to obtain a third data set; and

cross-correlating the third data set to obtain a fourth data set.

11. The method of claim 10 wherein the first filter comprises a median filter.

12. The method of claim 10 wherein the second filter comprises an FIR filter.

13. The method of claim 10 wherein the determining step further comprises peak-detecting the fourth data set.

14. The method of claim 13 wherein the peak-detecting step comprises sub-steps, the sub-steps comprising.

pre-determining a threshold peak value;

applying the threshold peak value to the fourth data set; and

marking peak amplitude values exceeding the threshold value.

15. The method of claim 14 further comprising sending a warning signal to the surface of the well if a significant number of the marked peak amplitude values occur for more than a predetermined amount of time.

16. The method of claim 15 wherein the predetermined amount of time comprises the range of five to ten cycles.

17. The method of claim 6 further comprising sending a warning signal to the surface of the well if torsional vibration is indicated.

18. The method of claim 17 further comprising changing at least one drilling parameter of the drilling operation in response to the warning signal.

19. The method of claim 18 wherein the at least one drilling parameter comprises a rotations per minute value of the drillstring.

20. The method of claim 18 wherein the at least one drilling parameter comprises a weight-on-bit value.

21. The method of claim 17 further comprising changing the downlink signal frequency in response to the warning signal.

22. A method of reducing noise caused by torsional vibration in a drillstring while drilling in a subterranean well, the drillstring being part of a drilling assembly having a mud pulse telemetry system capable of sending uplink or downlink signals, the method comprising:

detecting torsional vibration in the drillstring; and

changing the downlink signal frequency such that the torsional vibration frequency does not interfere with the downlink signal frequency.

23. A method of detecting torsional vibration in a drillstring while drilling in a subterranean well, the drillstring being part of a drilling assembly having a mud pulse telemetry system capable of sending uplink or downlink signals, the method comprising:

sampling a downhole pressure sensor at a frequency of at least 1 Hertz to obtain a first data set;

cross-correlating the first data set using a reference signal to obtain a second data set;

peak-detecting the second data set to determine whether the second data set indicates torsional vibration in the drillstring; and

sending a warning to the surface of the well if torsional vibration is indicated.

24. The method of claim 23 wherein the reference signal comprises a step function.

25. The method of claim 23 wherein the reference signal comprises a sinusoidal function.

26. The method of claim 23 further comprising:

calculating the torsional vibration frequency; and

filtering out the torsional vibration frequency.

27. The method of claim 26 wherein the filtering step further comprises using a hand pass filter.

29. The drilling assembly of claim 23 wherein the scheme further comprises:

a median filter;

an FIR filter;

a cross-correlation algorithm; and

a peak-detect algorithm for applying a pre-determined value to the pressure samples.

30. The drilling assembly of claim 24 further comprising a downhole transmitter for sending a warning signal to the surface of the well when a significant number of the pressure sample values exceed the predetermined value for a pre-determined amount of time.

31. The drilling assembly of claim 25 wherein the pre-determined amount is in the range of five to ten cycles.

28. A drilling assembly for detecting torsional vibration in a drillstring located in a subterranean well, the assembly comprising:

a pressure sensor for sampling the pressure in a flow of fluid being pumped downhole;

a control system for sampling the pressure sensor without stopping the fluid pumping; and

a scheme for detecting pressure samples caused by torsional vibration in the drillstring.