Well Monitoring by Means of Distributed Sensing Means

• US 20120063267A1
• Filed: 05/27/2010
• Published: 03/15/2012
• Est. Priority Date: 05/27/2009
• Status: Abandoned Application

• Current Assignee: Optasense Holdings Limited (Luna Innovations, Inc.)
• Original Assignee: Qinetiq Limited (QinetiQ Group PLC)
• Inventors: Hill, David John, McEwen-King, Magnus, Tindel, Patrick
• Application Number:
  US13/320,877
• Publication Number:
  US 20120063267A1
• Time in Patent Office: Days
• US Class Current: 367/82
• CPC Class Codes: E21B 43/11857 firing indication systems
• CPC Class Codes: E21B 43/26 by forming crevices or fractures
• CPC Class Codes: E21B 47/107 using acoustic means
• CPC Class Codes: E21B 47/135 using light waves, e.g. infrared or ultraviolet waves
• CPC Class Codes: E21B 47/16 through the drill string or casing , e.g. by torsional acoustic waves
• 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: G01V 1/50 Analysing data
• CPC Class Codes: G01V 2210/1429 Subsurface, e.g. in borehole or below weathering layer or mud line
• CPC Class Codes: G01V 2210/646 Fractures

Abstract

Methods and apparatus for downhole monitoring are provided by interrogating an unmodified optic fibre (102) arranged along the path of a well bore (106) to provide a distributed acoustic sensor and sampling data gathered from a plurality of contiguous sensing portions of the fibre. The sampled data is processed to determine one or more well bore parameters. The well bore parameters may comprise a well condition profile, and may be obtained in response to an acoustic stimulus.

Claims

1. A method for downhole monitoring comprising:

interrogating an unmodified optic fibre arranged along the path of a well bore to provide distributed acoustic sensing;

simultaneously sampling data gathered from a plurality of contiguous portions of said fibre; and

processing said data to determine one or more well bore parameters.

2. A method according to claim 1, wherein processing said data includes detecting a perforation event, and said parameters include the speed of an acoustic pulse in the well bore casing.

3. A method according to claim 1, wherein processing said data includes detecting at least one fracture event, and said parameters include at least one of:

depth of fracture, rate of fracturing, range of fracture, and fracture density.

4. A method according to claim 1, wherein processing said data includes detecting well fluid flow, and said parameters include flow rate and depth of flow.

5. A method according to claim 1, wherein processing comprises detecting multiple event types.

6. A method according to claim 1, wherein the sampling rate is greater than or equal to 1 kHz.

7. A method according to claim 1, wherein the sampling rate is greater than or equal to 5 kHz.

8. A method according to claim 1, wherein at least 100 channels are sampled simultaneously.

9. A method according to claim 1, wherein at least 250 channels are sampled simultaneously.

10. A method according to claim 1, wherein said channels correspond to contiguous portions of fibre less than or equal to 10 m in length.

11. A method according to claim 1, wherein processing said data comprises performing transient detection.

12. A method according to claim 11, wherein transient detection includes maintaining a measure of mean absolute deviation.

13. A method according to claim 12, wherein said measure of mean absolute deviation is updated by exponential averaging using a decay term, N.

14. A method according to claim 13, wherein said decay term N is adaptively varied.

15. A method according to claim 1, wherein processing said data comprises frequency analysis.

16. A method according to claim 1, wherein said data is processed in real time.

17. A method according to claim 1, further comprising adjusting interrogation parameters to vary the contiguous portions of fibre from which data is sampled.

18. A method according to claim 17, wherein said interrogation parameters are adjusted adaptively in response to detected events.

19. A method according to claim 1, wherein processing said data includes detecting the response to an acoustic stimulus, and wherein said parameter is a well condition profile.

20. A system for downhole monitoring, said system comprising:

a fibre optic interrogator adapted to provide distributed acoustic sensing on an unmodified fibre arranged along the path of a well bore;

a sampler arranged to sample a plurality of channels output from said interrogator simultaneously to provide acoustic data from a plurality of contiguous portions of said fibre at each of a plurality of times; and

a data analyser adapted to process said sampled data to detect well events and output parameters associated with detected events.

21. A system according to claim 20 adapted to detect multiple event types.

22. A system according to claim 20, adapted to detect both fracture events and fluid inflow.