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Fiber Bragg Grating Sensors for the Oil Industry

View Article: PubMed Central - PubMed

ABSTRACT

With the oil and gas industry growing rapidly, increasing the yield and profit require advances in technology for cost-effective production in key areas of reservoir exploration and in oil-well production-management. In this paper we review our group’s research into fiber Bragg gratings (FBGs) and their applications in the oil industry, especially in the well-logging field. FBG sensors used for seismic exploration in the oil and gas industry need to be capable of measuring multiple physical parameters such as temperature, pressure, and acoustic waves in a hostile environment. This application requires that the FBG sensors display high sensitivity over the broad vibration frequency range of 5 Hz to 2.5 kHz, which contains the important geological information. We report the incorporation of mechanical transducers in the FBG sensors to enable enhance the sensors’ amplitude and frequency response. Whenever the FBG sensors are working within a well, they must withstand high temperatures and high pressures, up to 175 °C and 40 Mpa or more. We use femtosecond laser side-illumination to ensure that the FBGs themselves have the high temperature resistance up to 1100 °C. Using FBG sensors combined with suitable metal transducers, we have experimentally realized high- temperature and pressure measurements up to 400 °C and 100 Mpa. We introduce a novel technology of ultrasonic imaging of seismic physical models using FBG sensors, which is superior to conventional seismic exploration methods. Compared with piezoelectric transducers, FBG ultrasonic sensors demonstrate superior sensitivity, more compact structure, improved spatial resolution, high stability and immunity to electromagnetic interference (EMI). In the last section, we present a case study of a well-logging field to demonstrate the utility of FBG sensors in the oil and gas industry.

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Reflection and transmission spectra of seed gratings (black curve) and regenerated fiber Bragg gratings (red curve).
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sensors-17-00429-f007: Reflection and transmission spectra of seed gratings (black curve) and regenerated fiber Bragg gratings (red curve).

Mentions: Regenerated fiber Bragg gratings (R-FBGs), which take advantage of a simple thermal annealing process, have successfully achieved operating temperatures up to 1100 °C. During the thermal regeneration process, a seed grating is gradually erased as the annealing temperature rises towards the “regeneration point”. Continued annealing at increased temperature causes the grating to grow again [128,129,130]. Regeneration of the grating is aided by use of high germania-content fiber and hydrogen loading prior to inscription of the seed grating [131], or by using helium-loaded germanosilicate optical fiber [132]. After regeneration, the RFBG shows narrower spectral bandwidth than the seed FBG, which is helpful in improving the filtering technology and sensor multiplexing, as shown in Figure 7. However, the reflectivity of the RFBG is always lower than that of its seed FBG, although many methods have been tried to improve the reflectivity. Another problem is that the heating process is complex, and it is necessary to monitor and control the spectral response during the regeneration process. RFBGs are mechanically weaker than conventional FBGs following the regeneration, which requires high temperatures, up to 800 °C. The mechanical degradation limits application of RGBGs in well-logging.


Fiber Bragg Grating Sensors for the Oil Industry
Reflection and transmission spectra of seed gratings (black curve) and regenerated fiber Bragg gratings (red curve).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5375715&req=5

sensors-17-00429-f007: Reflection and transmission spectra of seed gratings (black curve) and regenerated fiber Bragg gratings (red curve).
Mentions: Regenerated fiber Bragg gratings (R-FBGs), which take advantage of a simple thermal annealing process, have successfully achieved operating temperatures up to 1100 °C. During the thermal regeneration process, a seed grating is gradually erased as the annealing temperature rises towards the “regeneration point”. Continued annealing at increased temperature causes the grating to grow again [128,129,130]. Regeneration of the grating is aided by use of high germania-content fiber and hydrogen loading prior to inscription of the seed grating [131], or by using helium-loaded germanosilicate optical fiber [132]. After regeneration, the RFBG shows narrower spectral bandwidth than the seed FBG, which is helpful in improving the filtering technology and sensor multiplexing, as shown in Figure 7. However, the reflectivity of the RFBG is always lower than that of its seed FBG, although many methods have been tried to improve the reflectivity. Another problem is that the heating process is complex, and it is necessary to monitor and control the spectral response during the regeneration process. RFBGs are mechanically weaker than conventional FBGs following the regeneration, which requires high temperatures, up to 800 °C. The mechanical degradation limits application of RGBGs in well-logging.

View Article: PubMed Central - PubMed

ABSTRACT

With the oil and gas industry growing rapidly, increasing the yield and profit require advances in technology for cost-effective production in key areas of reservoir exploration and in oil-well production-management. In this paper we review our group’s research into fiber Bragg gratings (FBGs) and their applications in the oil industry, especially in the well-logging field. FBG sensors used for seismic exploration in the oil and gas industry need to be capable of measuring multiple physical parameters such as temperature, pressure, and acoustic waves in a hostile environment. This application requires that the FBG sensors display high sensitivity over the broad vibration frequency range of 5 Hz to 2.5 kHz, which contains the important geological information. We report the incorporation of mechanical transducers in the FBG sensors to enable enhance the sensors’ amplitude and frequency response. Whenever the FBG sensors are working within a well, they must withstand high temperatures and high pressures, up to 175 °C and 40 Mpa or more. We use femtosecond laser side-illumination to ensure that the FBGs themselves have the high temperature resistance up to 1100 °C. Using FBG sensors combined with suitable metal transducers, we have experimentally realized high- temperature and pressure measurements up to 400 °C and 100 Mpa. We introduce a novel technology of ultrasonic imaging of seismic physical models using FBG sensors, which is superior to conventional seismic exploration methods. Compared with piezoelectric transducers, FBG ultrasonic sensors demonstrate superior sensitivity, more compact structure, improved spatial resolution, high stability and immunity to electromagnetic interference (EMI). In the last section, we present a case study of a well-logging field to demonstrate the utility of FBG sensors in the oil and gas industry.

No MeSH data available.


Related in: MedlinePlus