Well monitoring by means of distributed sensing means

Patent metadata

Field	Value
Publication number	US-9689254-B2
Application number	US-201514816456-A
Country	US
Kind code	B2
Filing date	Aug 3, 2015
Priority date	May 27, 2009
Publication date	Jun 27, 2017
Grant date	Jun 27, 2017

Abstract

Methods and apparatus for downhole monitoring are provided by interrogating an unmodified optic fiber ( 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 fiber. 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.

First claim

The invention claimed is:

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;
wherein processing said data includes detecting the response to an acoustic stimulus, and
wherein said parameter is a well condition profile.

2. A method according to claim 1 , wherein said acoustic stimulus comprises a perforation event, and the step of determining said well condition profile comprises determining 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 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;
wherein said data analyser is configured to detect the response to an acoustic stimulus, and determine a well condition profile.

20. A system according to claim 19 adapted to detect multiple event types.

21. A system according to claim 19 , adapted to detect both fracture events and fluid inflow.

Assignees

• Optasense Holdings Ltd

Inventors

• Hill David John
• Mcewen-King Magnus
• Tindell Patrick

Classifications

• E21B47/135

  using light waves, e.g. infrared or ultraviolet waves · CPC title

• E21B47/107 Primary

  using acoustic means · CPC title

• E21B43/11857 Primary

  firing indication systems · CPC title

• G01V1/50

  Analysing data · CPC title

• G01V2210/1429

  Subsurface, e.g. in borehole or below weathering layer or mud line · CPC title