High speed distributed temperature sensing with auto correction

Patent metadata

Field	Value
Publication number	US-10119868-B2
Application number	US-201415324694-A
Country	US
Kind code	B2
Filing date	Sep 17, 2014
Priority date	Sep 17, 2014
Publication date	Nov 6, 2018
Grant date	Nov 6, 2018

Abstract

A system and method for a higher speed auto-correcting temperature measurement in a system using a fiber optic distributed sensor.

First claim

The invention claimed is:

1. A system for auto-correcting temperature measurement comprising:
a. a first source configured to provide a primary light signal;
b. a second source configured to provide a secondary light signal;
c. a distributed fiber optic sensor that receives the primary and secondary light signals and that is configured to generate back-scattered Stokes and anti-Stokes bands for each of the primary and secondary light signals, wherein a Rayleigh component of the primary light signal overlaps with the Stokes band of the secondary light signal and a Rayleigh component of the secondary light signal overlaps with the anti-Stokes band of the primary light signal;
d. a wave division multiplexer (WDM) for continuously receiving the primary light signal and the secondary light signal and passing a resulting combined signal into the distributed fiber optic sensor; wherein the WDM also acts as a de-multiplexer, separating the backscattered light from the distributed fiber optic sensor into an anti-Stokes band from the primary light signal and a Stokes band from the secondary light signal;
e. two notch filters that match the wavelengths of the Rayleigh components of the primary and secondary light signals and that continuously receive, from the WDM, the anti-Stokes band from the primary light signal and the Stokes band from the secondary light signal and filter out the Rayleigh components of the primary and secondary light signals;
f. two photo detectors for receiving signals from the notch filters and measure the intensity of each;
g. a signal processor configured to receive output from the photo detectors and to calibrate and measure the temperature distribution along said distributed fiber optic sensor based on the ratio of the intensity of the anti-Stokes band of the primary light signal and the Stokes band of the secondary light signal.

2. The system of claim 1 , wherein said primary light signal has a wavelength of about 975 nanometers and said secondary light signal has a wavelength of about 940 nanometers.

3. The system of claim 1 , wherein said primary light signal has a wavelength of about 1500 nanometers and said secondary light signal has a wavelength of about 1410 nanometers.

4. The system of claim 1 , wherein said primary light signal has a wavelength of about 1550 nanometers and said secondary light signal has a wavelength of about 1450 nanometers.

5. The system of claim 1 , wherein said primary light signal has a wavelength of about 1030 nanometers and said secondary light signal has a wavelength of about 990 nanometers.

6. The system of claim 1 , wherein the notch filters are tuned to the center of the Rayleigh wavelength of each of the primary and secondary light signals.

7. A method of auto-correcting temperature measurement in a system using a distributed fiber optic sensor, said method comprising:
a. feeding a primary light source energy into a wave division multiplexer;
b. feeding, during said feeding the primary light source energy, a secondary light source energy into the wave division multiplexer to create a combined primary and secondary light source energy;
c. feeding the combined primary and secondary light source energies into the distributed fiber optic sensor;
d. feeding back-scattered primary and secondary light source energy from the distributed fiber optic sensor into the wave division multiplexer that is configured to separate the back-scattered light source energy into a Raman anti-Stokes component of the primary light source energy and a Raman Stokes component of the secondary light source energy;
e. feeding the Raman anti-Stokes component of the primary light source energy through a first notch filter that filters out a back-scattered Rayleigh component of the secondary light source energy;
f. feeding the Raman Stokes component of the secondary light source energy through a second notch filter that filters out a back-scattered Rayleigh component of the primary light source energy;
g. continuously feeding the output of the two notch filters to two photo detectors to measure the signal intensities of back-scattered anti-Stokes signals of the primary light source energy and back-scattered Stokes signals of the secondary light source energy; and
h. calculating a temperature using the back-scattered anti-Stokes signal of the primary light source energy and the back-scattered Stokes signal of the secondary light source energy.

8. The method of claim 7 , wherein said primary light source energy has a wavelength of about 975 nanometers and said secondary light source enerav has a wavelength of about 940 nanometers.

9. The method of claim 7 , wherein said primary light source energy has a wavelength of about 1500 nanometers and said secondary light source energy has a wavelength of about 1410 nanometers.

10. The method of claim 7 , wherein said primary light source energy has a wavelength of about 1550 nanometers and said secondary light source energy has a wavelength of about 1450 nanometers.

11. The method of claim 7 , wherein said primary light source energy has a wavelength of about 1030 nanometers and said secondary light source energy has a wavelength of about 990 nanometers.

12. The method of claim 7 , wherein the notch filters are tuned to the center of the Rayleigh wavelength of each light source energy.

13. The method of claim 7 , wherein said calculating step is performed without measuring or using differential attention profiles.

Assignees

• Halliburton Energy Services Inc

Inventors

• Therrien Jason E
• Jaaskelainen Mikko

Classifications

• G01K2011/324

  Physics · mapped topic

• G01K15/005 Primary

  Calibration · CPC title

• G01J5/0821

  Optical fibres · CPC title

• G01J2005/0048

  Physics · mapped topic

• G01K11/32

  using changes in transmittance, scattering or luminescence in optical fibres · CPC title