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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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(a) Cross-sectional photomicrograph of the MCF-FBG; (b) Refractive index profile of the MCF-cross section; (c) Longitudinal photomicrograph of gratings inside MFC; (d) Schematic of the vector grating; (e) Spectra of the vector-FBG; (f) Angular dependence of acceleration responsivity of this sensor.
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sensors-17-00429-f006: (a) Cross-sectional photomicrograph of the MCF-FBG; (b) Refractive index profile of the MCF-cross section; (c) Longitudinal photomicrograph of gratings inside MFC; (d) Schematic of the vector grating; (e) Spectra of the vector-FBG; (f) Angular dependence of acceleration responsivity of this sensor.

Mentions: We recently demonstrated a 2D vector vibrometer based on direct power detection of orthogonal cladding FBG reflections. The sensing probe consists of a compact structure in which a short section of the multi-clad fiber (MCF) containing two orthogonally cascaded cladding FBGs is spliced to SMF with self-alignment process. We wrote the two gratings, azimuthally separated by 90°, using femtosecond laser side-illumination, taking care to ensure the two grating inscriptions are precisely positioned and compact in size, as show in Figure 6c,d. With such configuration, as shown in Figure 6e, the reflection spectra show pairs of well defined cladding resonances from the internal cladding (two weak resonances at shorter wavelength side) and from the fiber core (two strong resonances at longer wavelength side). Most importantly, the cladding resonances are strongly directional sensitive to the small fiber bending, and the orientation of vibration can be determined in a two dimensional plane. Any optical power fluctuations are referenced out by core Bragg resonances that are insensitive to fiber bending. When the dual cladding FBGs work as an accelerometer, the intensities of the cladding mode resonances present strongly orthogonal responses thanks to the two orthogonally positioned gratings in the cladding. Figure 6f demonstrates the angular dependence of acceleration responsivity of sensor. In future work, the 2D direction information can be achieved by analyzing this 2D vibration response.


Fiber Bragg Grating Sensors for the Oil Industry
(a) Cross-sectional photomicrograph of the MCF-FBG; (b) Refractive index profile of the MCF-cross section; (c) Longitudinal photomicrograph of gratings inside MFC; (d) Schematic of the vector grating; (e) Spectra of the vector-FBG; (f) Angular dependence of acceleration responsivity of this sensor.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

sensors-17-00429-f006: (a) Cross-sectional photomicrograph of the MCF-FBG; (b) Refractive index profile of the MCF-cross section; (c) Longitudinal photomicrograph of gratings inside MFC; (d) Schematic of the vector grating; (e) Spectra of the vector-FBG; (f) Angular dependence of acceleration responsivity of this sensor.
Mentions: We recently demonstrated a 2D vector vibrometer based on direct power detection of orthogonal cladding FBG reflections. The sensing probe consists of a compact structure in which a short section of the multi-clad fiber (MCF) containing two orthogonally cascaded cladding FBGs is spliced to SMF with self-alignment process. We wrote the two gratings, azimuthally separated by 90°, using femtosecond laser side-illumination, taking care to ensure the two grating inscriptions are precisely positioned and compact in size, as show in Figure 6c,d. With such configuration, as shown in Figure 6e, the reflection spectra show pairs of well defined cladding resonances from the internal cladding (two weak resonances at shorter wavelength side) and from the fiber core (two strong resonances at longer wavelength side). Most importantly, the cladding resonances are strongly directional sensitive to the small fiber bending, and the orientation of vibration can be determined in a two dimensional plane. Any optical power fluctuations are referenced out by core Bragg resonances that are insensitive to fiber bending. When the dual cladding FBGs work as an accelerometer, the intensities of the cladding mode resonances present strongly orthogonal responses thanks to the two orthogonally positioned gratings in the cladding. Figure 6f demonstrates the angular dependence of acceleration responsivity of sensor. In future work, the 2D direction information can be achieved by analyzing this 2D vibration response.

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