Method and apparatus for optical sensing

• US 9,804,021 B2
• Filed: 02/19/2016
• Issued: 10/31/2017
• Est. Priority Date: 05/27/2009
• Status: Active Grant

• Current Assignee: Silixa Limited
• Original Assignee: Silixa Limited
• Inventors: Farhadiroushan, Mahmoud, Parker, Tom Richard, Shatalin, Sergey
• Primary Examiner(s): Radkowski, Peter
• Application Number:
  US15/048,315
• Publication Number:
  US 20160169712A1
• Time in Patent Office: 620 Days
• CPC Class Codes: E21B 47/002 by visual inspection
• CPC Class Codes: E21B 47/0025 generating an image of the borehole wall using down-hole measurements, e.g. acoustic or electric
• CPC Class Codes: E21B 47/107 using acoustic means
• CPC Class Codes: G01D 5/35303 using a reference fibre, e.g. interferometric devices
• CPC Class Codes: G01D 5/35306 using an interferometer arrangement
• CPC Class Codes: G01D 5/35325 using interferometer with two arms in reflection, e.g. Mickelson interferometer
• CPC Class Codes: G01D 5/35335 Aspects of emitters or receivers used by an interferometer in an optical fibre sensor arrangement using multiple sensor devices using multiplexing techniques G01D5/35383
• CPC Class Codes: G01D 5/35358 using backscattering to detect the measured quantity
• CPC Class Codes: G01D 5/35364 using inelastic backscattering to detect the measured quantity, e.g. using Brillouin or Raman backscattering
• CPC Class Codes: G01D 5/35377 Means for amplifying or modifying the measured quantity
• CPC Class Codes: G01D 5/35383 using multiple sensor devices using multiplexing techniques
• CPC Class Codes: G01F 1/66 by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
• CPC Class Codes: G01F 1/661 using light
• CPC Class Codes: G01F 1/662 Constructional details
• CPC Class Codes: G01F 1/666 by detecting noise and sounds generated by the flowing fluid
• CPC Class Codes: G01F 1/667 Arrangements of transducers for ultrasonic flowmeters; Circuits for operating ultrasonic flowmeters
• CPC Class Codes: G01H 9/004 using fibre optic sensors light guides per se G02B6/00, acousto-optical devices specially adapted for gating or modulating in optical wave guides G02F1/125
• CPC Class Codes: G01M 11/085 the optical fiber being on or near the surface of the DUT
• CPC Class Codes: G01M 11/331 by using interferometer
• CPC Class Codes: G01M 3/24 using infrasonic, sonic, or ultrasonic vibrations
• CPC Class Codes: G01M 5/0058 : of elongated objects, e.g. pipes, masts, towers or railways
• CPC Class Codes: G01M 5/0066 : by exciting or detecting vibration or acceleration vibration testing of structures G01M7/00
• CPC Class Codes: G01M 5/0091 : by using electromagnetic excitation or detection
• CPC Class Codes: G01V 1/226 : Optoseismic systems
• CPC Class Codes: G01V 1/40 : specially adapted for well-logging

Abstract

Apparatus and methods for fast quantitative measurement of perturbation of optical fields transmitted, reflected and/or scattered along a length of an optical fibre can be used for point sensors as well as distributed sensors or the combination of both. In particular, this technique can be applied to distributed sensors while extending dramatically the speed and sensitivity to allow the detection of acoustic perturbations anywhere along a length of an optical fibre while achieving fine spatial resolution. Advantages of this technique include a broad range of acoustic sensing and imaging applications. Typical uses are for monitoring oil and gas wells such as for distributed flow metering and/or imaging, seismic imaging, monitoring long cables and pipelines, imaging within large vessel as well as for security applications.

Claims

1. An apparatus, comprising:

a distributed acoustic sensor (DAS) system having a fibre optic cable deployed in use along a pipe to be monitored, the distributed acoustic sensor system receiving backscattered and/or reflected light from along the optical fibre and determining acoustic signals incident along the fibre optic cable therefrom;

wherein the distributed acoustic sensor system is arranged to monitor fluid flow in the pipe by determining the speed of sound in one or both directions of fluid flow.

2. An apparatus according to claim 1, wherein the determined speed of sound is used to determine the flow profile along the pipe.

3. An apparatus according to claim 1, wherein the fluid flow monitoring comprises tracking vortices induced pressure waves.

4. An apparatus according to claim 1, wherein the fluid flow monitoring comprises tracking acoustic waves generated and propagated along the pipe.

5. An apparatus according claim 1, wherein the fluid flow monitoring further comprises tracking eddies generated within the flow to determine the flow rate.

6. An apparatus according to claim 1, wherein the DAS system further comprises an interferometer arranged to receive the backscattered and/or reflected light from along the optical fibre, the interferometer comprising at least two optical paths with a path length difference therebetween, the backscattered and/or reflected light interfering in the interferometer to produce interference components, the DAS system further comprising plural photodetectors to measure the interference components, and a processor arranged to determine the optical phase angle data therefrom.

7. A method of distributed acoustic sensing, comprising:

determining acoustic signals incident along a pipe using a distributed acoustic sensor (DAS) system having a fibre optic cable deployed in use along the pipe, the distributed acoustic sensor system receiving backscattered and/or reflected light from along the optical fibre; and

monitoring fluid flow in the pipe using the distributed acoustic sensor system by determining the speed of sound in one or both directions of fluid flow.

8. A method according to claim 7, wherein the determined speed of sound is used to determine the flow profile along the pipe.

9. A method according to claim 7, wherein the fluid flow monitoring further comprises tracking vortices induced pressure waves.

10. A method according to claim 7, wherein the fluid flow monitoring further comprises tracking acoustic waves generated and propagated along the pipe.

11. A method according to claim 7, wherein the fluid flow monitoring further comprises tracking eddies generated within the flow to determine the flow rate.

12. A method according to claim 7, wherein the DAS system further comprises an interferometer arranged to receive the backscattered and/or reflected light from along the optical fibre, the interferometer comprising at least two optical paths with a path length difference therebetween, the backscattered and/or reflected light interfering in the interferometer to produce interference components, the DAS system further comprising plural photodetectors to measure the interference components, and a processor arranged to determine the optical phase angle data therefrom.

13. An apparatus, comprising:

a distributed acoustic sensor (DAS) system having a fibre optic cable deployed in use along a pipe to be monitored, the distributed acoustic sensor system receiving backscattered and/or reflected light from along the optical fibre and determining acoustic signals incident along the fibre optic cable therefrom;

wherein the distributed acoustic sensor system is arranged to monitor fluid flow in the pipe by tracking eddies generated within the flow over a section of the pipe to determine the flow rate.

14. An apparatus according to claim 13, wherein the fluid flow monitoring comprises tracking acoustic waves generated and propagated along the pipe.

15. An apparatus according to claim 13, wherein the fluid flow monitoring further comprises determining the speed of sound in one or both directions of fluid flow.

16. An apparatus according to claim 15, wherein the determined speed of sound is used to determine the flow profile along the pipe.

17. An apparatus according to claim 13, wherein the fluid flow monitoring further comprises noise spectrum correlation techniques over a section of the pipe.

18. An apparatus according to claim 13, wherein the DAS system further comprises an interferometer arranged to receive the backscattered and/or reflected light from along the optical fibre, the interferometer comprising at least two optical paths with a path length difference therebetween, the backscattered and/or reflected light interfering in the interferometer to produce interference components, the DAS system further comprising plural photodetectors to measure the interference components, and a processor arranged to determine the optical phase angle data therefrom.

19. A method of distributed acoustic sensing, comprising:

determining acoustic signals incident along a pipe using a distributed acoustic sensor (DAS) system having a fibre optic cable deployed in use along the pipe, the distributed acoustic sensor system receiving backscattered and/or reflected light from along the optical fibre; and

monitoring fluid flow in the pipe using the distributed acoustic sensor system by tracking eddies generated within the flow over a section of the pipe to determine flow rate.

20. A method according to claim 19, wherein the fluid flow monitoring comprises tracking acoustic waves generated and propagated along the pipe.

21. A method according to claim 19, wherein the fluid flow monitoring further comprises determining the speed of sound in one or both directions of fluid flow.

22. A method according to claim 21, wherein the determined speed of sound is used to determine the flow profile along the pipe.

23. A method according to claim 19, wherein the fluid flow monitoring further comprises noise spectrum correlation techniques over a section of the pipe.

24. A method according to claim 19, wherein the DAS system further comprises an interferometer arranged to receive the backscattered and/or reflected light from along the optical fibre, the interferometer comprising at least two optical paths with a path length difference therebetween, the backscattered and/or reflected light interfering in the interferometer to produce interference components, the DAS system further comprising plural photodetectors to measure the interference components, and a processor arranged to determine the optical phase angle data therefrom.