Acoustic illumination for flow-monitoring

Patent metadata

Field	Value
Publication number	US-9896929-B2
Application number	US-201314440138-A
Country	US
Kind code	B2
Filing date	Nov 1, 2013
Priority date	Nov 2, 2012
Publication date	Feb 20, 2018
Grant date	Feb 20, 2018

Abstract

Externally generated noise can be coupled into a fluid carrying structure such as a pipe, well, or borehole so as to artificially acoustically “illuminate” the pipe, well, or borehole, and allow fluid flow in the structure or structural integrity to be determined. In the disclosed system, externally generated noise is coupled into the structure being monitored at the same time as data logging required to undertake the monitoring is performed. This has three effects. First, the externally generated sound is coupled into the structure so as to “illuminate” acoustically the structure to allow data to be collected from which fluid flow may be determined, and secondly the amount of data that need be collected is reduced, as there is no need to log data when the structure is not being illuminated. Thirdly, there are signal processing advantages in having the data logging being undertaken only when the acoustic illumination occurs.

First claim

The invention claimed is:

1. A method of monitoring a fluid-flow carrying structure, the method comprising:
obtaining acoustic data corresponding to acoustic energy sensed using an optical fiber distributed acoustic sensor at the same time as an acoustic wave is incident on the structure, the acoustic energy being coupled into the fluid-flow carrying structure from the incident acoustic wave; and
calculating a speed of sound in a fluid flow within the structure from the acoustic data, the calculating comprising:
plotting the acoustic data as a two-dimensional space-time image;
applying a two dimensional Fourier transform to the two-dimensional space-time image to obtain a transformed image;
in the transformed image, identifying gradients in the transformed image, the identified gradients corresponding to the respective speeds of sound, or at least a property or derivative thereof, of the coupled acoustic energy in the fluid flow within the structure in opposite directions along the fluid flow carrying structure; and
calculating the fluid flow in dependence on a difference between the respective speeds of sound in the fluid flow in the opposite directions.

2. A system for monitoring a fluid-flow carrying structure, the system comprising:
a processor arranged in use to:
obtain acoustic data corresponding to acoustic energy sensed using an optical fiber distributed acoustic sensor at the same time as an acoustic wave is incident on the structure, the acoustic energy being coupled into the fluid-flow carrying structure from the incident acoustic wave; and
calculate a speed of sound in a fluid flow within the structure from the acoustic data, the calculating comprising:
plotting the acoustic data as a two-dimensional space-time image;
applying a two dimensional Fourier transform to the two-dimensional space-time image to obtain a transformed image;
in the transformed image, identifying gradients in the transformed image, the identified gradients corresponding to the respective speeds of sound, or at least a property or derivative thereof, of the coupled acoustic energy in the fluid flow within the structure in opposite directions along the fluid flow carrying structure; and
calculating the fluid flow in dependence on a difference between the respective speeds of sound in the fluid flow in the opposite directions.

Assignees

• Silixa Ltd

Inventors

• Farhadiroushan Mahmoud
• Parker Tom
• Finfer Daniel
• Mahue Veronique

Classifications

• G01P5/241 Primary

  by using reflection of acoustical waves, i.e. Doppler-effect · CPC title

• E21B47/135 Primary

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

• E21B47/0224

  using seismic or acoustic means · CPC title

• G01V11/00

  Prospecting or detecting by methods combining techniques covered by two or more of main groups G01V1/00 - G01V9/00 · CPC title

• G01V1/226

  Optoseismic systems · CPC title