Methods and systems for use with a positive displacement motor

Patent metadata

Field	Value
Publication number	US-11066918-B2
Application number	US-201716096829-A
Country	US
Kind code	B2
Filing date	Apr 19, 2017
Priority date	Apr 26, 2016
Publication date	Jul 20, 2021
Grant date	Jul 20, 2021

Abstract

A method for determining a rotational frequency of a positive displacement motor positioned in a downhole portion of a drill string, the method including: providing at least one measurement device for measuring a property of a part of the drill string; providing a processor for processing a signal output by the at least one measurement device; operating the positive displacement motor whilst the part of the drill string is in a non-driven state; receiving the signal at the processor; determining, using the processor, a frequency spectrum of the signal; and determining the rotational frequency of the positive displacement motor by: identifying a peak in the frequency spectrum in a pre-determined frequency range associated with an expected rotational frequency of the positive displacement motor; and/or identifying a peak in the frequency spectrum having a pre-determined peak width associated with an expected rotational frequency of the positive displacement motor.

First claim

The invention claimed is:

1. A method for determining a rotational frequency of a positive displacement motor positioned in a downhole portion of a drill string, the method comprising:
providing at least one measurement device for measuring a property of a part of the drill string;
providing a processor for processing a signal output by the at least one measurement device, the signal including measurements of the property;
operating the positive displacement motor while the part of the drill string is in a non-driven state;
receiving the signal at the processor;
determining, using the processor, a frequency spectrum of the measurements of the property in the signal; and
determining the rotational frequency of the positive displacement motor by identifying a peak in the frequency spectrum of the measurements of the property from the signal and based upon a comparison of one or more widths of peaks in the frequency spectrum compared to a pre-determined peak width.

2. The method of claim 1 , wherein the property is vibrational motion of the part of the drill string.

3. The method of claim 1 , wherein the property is lateral motion of the part of the drill string.

4. The method of claim 1 , wherein the property is axial motion of the part of the drill string.

5. The method of claim 1 , wherein the property is tangential motion of the part of the drill string.

6. The method of claim 1 , wherein the at least one measurement device is an accelerometer.

7. The method of claim 1 , wherein the property is angular motion of the part of the drill string.

8. The method of claim 7 , wherein the at least one measurement device is a rate gyroscope/gyrometer for sensing the rate of change of the angular motion.

9. The method of claim 7 , wherein the at least one measurement device is a magnetometer.

10. The method of claim 1 , wherein the property is deformation of the part of the drill string.

11. The method of claim 10 , wherein the least one measurement device is a strain gauge.

12. The method of claim 1 , further comprising:
providing a plurality of measurement devices for measuring different properties of the part of the drill string; and
selectively providing the processor with a signal output by one of the plurality of measurement devices.

13. The method of claim 1 , wherein the step of determining, using the processor, a frequency spectrum of the signal comprises performing on the signal one of a Fourier transform, a wavelet transform, a sine transform, or a cosine transform.

14. The method of claim 1 , comprising:
providing a section of pipe for connecting to the drill string above the positive displacement motor, wherein the section of pipe is asymmetric with respect to a longitudinal axis of the drill string.

15. The method of claim 1 , wherein the at least one measurement device is provided on the drill string.

16. A method for determining a rotational frequency of a positive displacement motor positioned in a downhole portion of a drill string, the method comprising:
receiving a signal from at least one measurement device for measuring a property of a part of the drill string during operation of the positive displacement motor while the part of the drill string is in a non-driven state;
determining a frequency spectrum of the measured property in the signal; and
determining the rotational frequency of the positive displacement motor by identifying a peak in the frequency spectrum associated with an expected rotational frequency of the positive displacement motor and by comparing one or more widths of peaks in the frequency spectrum to a pre-determined peak width.

17. The method of claim 16 , further comprising:
controlling the operation of one or more aspects of the drill string in response to the determined rotational frequency.

18. The method of claim 16 , further comprising:
determining whether the part of the drill string is in a non-driven state and outputting the rotational frequency of the positive displacement motor at a first rate when it is determined that the drill string is in a non-driven state and at a second rate when it is determined that the drill string is in a driven state, wherein the second rate is lower than the first rate.

19. A system for determining a rotational frequency of a positive displacement motor positioned in a downhole portion of a drill string configured to perform the method of claim 16 .

20. The method of claim 1 , wherein determining the rotational frequency of the positive displacement motor further includes identifying a peak in the frequency spectrum of the measurements of the property from the signal and within a pre-determined frequency range associated with an expected rotational frequency of the positive displacement motor.

Assignees

• Schlumberger Technology Corp

Inventors

• Jeffryes Benjamin Peter

Classifications

• E21B4/02 Primary

  Fluid rotary type drives · CPC title

• G01P3/44 Primary

  for measuring angular speed (G01P3/56 takes precedence) · CPC title

• G01P3/02

  Devices characterised by the use of mechanical means · CPC title

• E21B21/08

  Controlling or monitoring pressure or flow of drilling fluid, e.g. automatic filling of boreholes, automatic control of bottom pressure (valve arrangements therefor E21B21/10) · CPC title

• E21B47/00 Primary

  Survey of boreholes or wells (monitoring pressure or flow of drilling fluid E21B21/08) · CPC title