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Proceedings Paper

Micro-structured fiber Bragg grating based pressure sensors in a downhole-like hydrogen rich environment
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Paper Abstract

The applicability of fiber Bragg gratings written in highly birefringent Butterfly micro-structured optical fibers (MSFBG) for simultaneous High Pressure/High Temperature monitoring without a significant pressure/temperature cross sensitivity have recently been shown. This makes these MS-FBG sensors extremely interesting for downhole monitoring in the Oil and Gas industry. However, an important effect to be taken into account for these applications is the presence of hydrogen, as hydrogen is known to diffuse into the fiber structure and therefore might affect the wavelength responses of the sensor element. In this paper, the effect of hydrogen gas on the MS-FBG sensor readings by monitoring the wavelength changes of the MS-FBG sensor in a hydrogen rich environment have been investigated.

In this experiments, two MS-FBG sensors were placed in a hydrogen test chamber: one with its fiber end sealed for pressure sensing and the other with its fiber end kept open for referencing purposes. It could be demonstrated that both sensors show a similar wavelength shift after some time and that due to the hydrogen diffusion, the pressure in the airholes of the sealed MS-FBG sensor equalizes the hydrogen pressure in the chamber. Furthermore, it could be demonstrated that the refractive index seen by the waveguide of the fiber is also affected. Based on all these observations, the influence of the hydrogen on the temperature and pressure measurement performance of the MS-FBG sensor is estimated, and a mitigation scheme that partially compensates for this influence is discussed.

Paper Details

Date Published: 9 May 2018
PDF: 8 pages
Proc. SPIE 10680, Optical Sensing and Detection V, 106800L (9 May 2018); doi: 10.1117/12.2306129
Show Author Affiliations
Ji-Ying Huang, Univ. de Mons (Belgium)
FBGS International FV (Belgium)
Jan Van Roosbroeck, FBGS International NV (Belgium)
Johan Vlekken, FBGS International NV (Belgium)
Damien Kinet, Univ. de Mons (Belgium)
Antonio Bueno Martinez, Univ. de Mons (Belgium)
Thomas Geernaert, Vrije Univ. Brussel (Belgium)
Flanders Make (Belgium)
Francis Berghmans, Vrije Univ. Brussel (Belgium)
Flanders Make (Belgium)
Bram Van Hoe, FBGS International NV (Belgium)
Eric Lindner, FBGS International NV (Belgium)
Christophe Caucheteur, Univ. de Mons (Belgium)

Published in SPIE Proceedings Vol. 10680:
Optical Sensing and Detection V
Francis Berghmans; Anna G. Mignani, Editor(s)

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