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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.

No MeSH data available.


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(a) Reflection and transmission spectrum of FBG written in a SMF (inset is imaging photo of FBG); (b) FBG wavelength versus temperature up to 1100 °C.
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sensors-17-00429-f008: (a) Reflection and transmission spectrum of FBG written in a SMF (inset is imaging photo of FBG); (b) FBG wavelength versus temperature up to 1100 °C.

Mentions: In the last few years, FBG fabrication using femtosecond laser has attracted considerable attention from researchers. Smelser et al. realized the formation of two grating types in SMF-28 fiber by focusing 125 fs, 0.5–2 mJ pulse laser through a phase mask onto a fiber sample [133]. The first type, designated “type I-IR”, appears below the damage threshold of the fiber material. The further thermal testing suggests that this I-IR grating is formed by a nonlinear absorption process, possibly resulting in the formation of color centers in the germanosilicate core glass. The second type, specified as “type II-IR”, appears with lased white light formation on the fiber. The type II-IR grating is most likely a consequence of damage to the germanosilicate core glass following ionization, and is possible for these gratings to withstand high temperatures. Thermal stability tests show that femtosecond laser-inscribed type II-IR FBGs exhibit excellent stability at temperatures slightly in excess of 1000 °C. This thermal stability has been attributed to the modification of the fiber core glass by the high peak power and the effects of nonlinear light-material interaction under irradiation by the femtosecond laser. On the support of the phase mask technique, the FBGs inscription over many kinds of fiber are realized easily. Compared to the conventional FBGs written using UV lasers, larger refractive index modification can be induced in fibers by femtosecond laser for its ultrashort pulse width and high peak power. Both the reflectance and transmission spectra of conventional FBGs are complementary and do not present obviously coupling loss. As for the high-temperature stability, conventional FBGs possess poor stability of temperature and they can be wiped out at high temperature below the melting transition temperature of silica fiber. But type II-IR FBGs by fetomsecond laser perform better and the high-temperature stability can be up to 1000 °C. Besides, fs-written type II-IR FBGs have the shorter lengths and higher reflectivities due to a larger refractive index contrast. On the other hand, the inscription of FBGs by femtosecond laser also brings some drawbacks, such as wide spectral bandwidth, low mechanical strength, large birefringence effect and cladding modes resonances, etc. Figure 8a shows the reflection and transmission spectrum of FBG written in a SMF. Due to the large spectral content of the femtosecond pulse after passing through the phase mask, it would be broadly dispersed and the energy spreads over a large area. As a result, some cladding modes resonances appear in the transmission spectrum, waiting for the further technique to eliminate these unexpected resonances.


Fiber Bragg Grating Sensors for the Oil Industry
(a) Reflection and transmission spectrum of FBG written in a SMF (inset is imaging photo of FBG); (b) FBG wavelength versus temperature up to 1100 °C.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

sensors-17-00429-f008: (a) Reflection and transmission spectrum of FBG written in a SMF (inset is imaging photo of FBG); (b) FBG wavelength versus temperature up to 1100 °C.
Mentions: In the last few years, FBG fabrication using femtosecond laser has attracted considerable attention from researchers. Smelser et al. realized the formation of two grating types in SMF-28 fiber by focusing 125 fs, 0.5–2 mJ pulse laser through a phase mask onto a fiber sample [133]. The first type, designated “type I-IR”, appears below the damage threshold of the fiber material. The further thermal testing suggests that this I-IR grating is formed by a nonlinear absorption process, possibly resulting in the formation of color centers in the germanosilicate core glass. The second type, specified as “type II-IR”, appears with lased white light formation on the fiber. The type II-IR grating is most likely a consequence of damage to the germanosilicate core glass following ionization, and is possible for these gratings to withstand high temperatures. Thermal stability tests show that femtosecond laser-inscribed type II-IR FBGs exhibit excellent stability at temperatures slightly in excess of 1000 °C. This thermal stability has been attributed to the modification of the fiber core glass by the high peak power and the effects of nonlinear light-material interaction under irradiation by the femtosecond laser. On the support of the phase mask technique, the FBGs inscription over many kinds of fiber are realized easily. Compared to the conventional FBGs written using UV lasers, larger refractive index modification can be induced in fibers by femtosecond laser for its ultrashort pulse width and high peak power. Both the reflectance and transmission spectra of conventional FBGs are complementary and do not present obviously coupling loss. As for the high-temperature stability, conventional FBGs possess poor stability of temperature and they can be wiped out at high temperature below the melting transition temperature of silica fiber. But type II-IR FBGs by fetomsecond laser perform better and the high-temperature stability can be up to 1000 °C. Besides, fs-written type II-IR FBGs have the shorter lengths and higher reflectivities due to a larger refractive index contrast. On the other hand, the inscription of FBGs by femtosecond laser also brings some drawbacks, such as wide spectral bandwidth, low mechanical strength, large birefringence effect and cladding modes resonances, etc. Figure 8a shows the reflection and transmission spectrum of FBG written in a SMF. Due to the large spectral content of the femtosecond pulse after passing through the phase mask, it would be broadly dispersed and the energy spreads over a large area. As a result, some cladding modes resonances appear in the transmission spectrum, waiting for the further technique to eliminate these unexpected resonances.

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