Well Monitoring by Means of Distributed Sensing Means

• US 20120057432A1
• Filed: 05/27/2010
• Published: 03/08/2012
• Est. Priority Date: 05/27/2009
• Status: Active Grant

• Current Assignee: Optasense Holdings Limited (Luna Innovations, Inc.)
• Original Assignee: Qinetiq Limited (QinetiQ Group PLC)
• Inventors: Hill, David John, McEwen-King, Magnus, Tindel, Patrick
• Granted Patent: US 9,617,848 B2
• Time in Patent Office: Days
• US Class Current: 367/81
• 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

This application describes methods and apparatus for downhole monitoring in real-time. The method involves 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 sensing portions of the fibre. The sampled data is then processed to provide a real-time indication of the acoustic signals detected by the sensing portions of the fibre. The real-time indication provides information to an operator or controller of the downwell process with real-time feedback data regarding what is happening during the down-well process which allows the identification of any problems and adjustment of the process parameters.

Claims

1. A method of monitoring a downhole process comprising:

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

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

processing said data to provide a real-time indication of the acoustic signals detected by at least one longitudinal sensing portion of said fibre.

2. A method as claimed in claim 1 wherein the said optic fibre is arranged in the well bore in which said downhole process is being performed.

3. A method as claimed in claim 1 wherein said real-time indication comprises an audible signal representing the acoustic signals detected by at least one longitudinal portion of fibre in the vicinity of the downhole process.

4. A method as claimed in claim 1 wherein said real-time indication comprises an indication of the intensity of acoustic signals detected by at least one longitudinal sensing portion of fibre in the vicinity of the downhole process.

5. A method as claimed in claim 1 wherein said step of processing said data comprises performing frequency analysis.

6. A method as claimed in claim 5 wherein said real-time indication comprises an indication of the frequency of acoustic signals detected by at least one longitudinal portion of fibre in the vicinity of the downhole process.

7. A method as claimed in claim 1 wherein the step of processing said data comprises analysing the data to detect an event of interest and said real-time indication comprises an indication that said event has been detected.

8. A method as claimed in claim 7 wherein said step of analysing said data comprises analysing the data for at least one predefined acoustic characteristic.

9. A method as claimed in claim 1 wherein said downhole process comprises one of:

perforation charge placement;

perforation charge firing;

hydraulic fracturing;

tool deployment;

drilling of plugs; and

production flow.

10. A method as claimed in claim 1 wherein the steps of interrogating the fibre, sampling data and processing data comprise launching a series of optical pulses into said fibre and detecting radiation Rayleigh backscattered by the fibre;

and processing the detected Rayleigh backscattered radiation to provide a plurality of discrete longitudinal sensing portions of the fibre.

11. A method as claimed in claim 1 wherein said optic fibre is single mode fibre which is, absent of any external stimulus, free of any substantial change of optical properties along its length.

12. A method as claimed in claim 1 where the longitudinal sensing portions of fibre are 10 m or less in length.

13. A method according to claim 1 wherein said sampling is performed at a sampling rate greater than or equal to 5 kHz.

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

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

16. A method of controlling a downhole process comprising:

performing said downhole process;

monitoring said downhole process using the method as claimed in any preceding claim; and

adjusting the operation of said process as appropriate in response to said real-time indication.

17. A method as claimed in claim 16 wherein said method comprises automatically adjusting at least one parameter of said downhole process in response to said real-time indication.

18. A computer program product which, when run on a suitably programmed computer connected to or embodied within a controller for an optical interrogator or a downhole fibre optic, performs the method of claim 1.

19. A method of downhole operation comprising;

performing a downhole process;

receiving real-time acoustic data feedback from a downhole distributed acoustic sensor regarding the operation of said process; and

controlling said downhole process based on said acoustic data feedback.

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

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

a sampler arranged to sample a plurality of channels output from said interrogator to provide real-time acoustic data from a plurality of longitudinal portions of said fibre; and

an interface device configured to output a real-time indication of the acoustic signals detected by at least one longitudinal sensing portion of said fibre.

21. A system according to claim 20 wherein said interface device comprises an audio device for producing an audible signal based on the acoustic signals detected by at least one longitudinal portion of fibre in the vicinity of the downhole process.

22. A system according to claim 20 wherein said interface device comprises a display device and wherein said wherein said real-time indication comprises an indication of the intensity of acoustic signals detected by at least one longitudinal sensing portion of fibre in the vicinity of the downhole process.

23. A system for controlling a downhole process comprising:

a controller for controlling process parameters; and

a monitoring system as claimed in claim 20;

wherein

said controller is responsive to said real-time indication generated by said monitoring system to control said process parameters.

24. The use of distributed acoustic sensing to provide real-time feedback to the operator of a downhole process of the acoustic signals generated by said downhole process.