TiO2 coated optical fibers for distributed real-time pH monitoring in wellbore conditions

Shumski, Alexander; Diemler, Nathan; Wright, Ruishu; Lü, Fei; Ohodnicki, Paul R.; Su, Yang-Duan

doi:10.1117/12.2618836

Cited by 2 publications

(13 citation statements)

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“…Sol-gel TiO2 transmission was the subject of several previous publications from the authors, and our results also exhibited the typical pattern of this variety of TiO2-coated optical fibers to show increased transmission in basic solutions relative to neutral ones (Figure 5, 0-165 minutes) at ambient conditions, following a slow initial "activation" step when first exposed to the basic solution. 7 In order to better approximate the conditions expected in subsurface storage wells and capped wellbores, higher pressure measurements were collected after the first two cycles were shown to exhibit a typical base response at ambient pressure. The vessel was pressurized to 64.4 bar (934 psi) in neutral conditions, and then held for 30 minutes with minimal observable response to the pressure change.…”

Section: Transmission Results Of Tio2-coated Optical Fibers For Ph Se...mentioning

confidence: 99%

“…A film of TiO2 was coated onto the unjacketed coreless fiber using a previously reported sol-gel method. 7,10 To prepare the sol-gel, 1.0 mL of titanium (IV) isopropoxide was mixed with 7.5 mL isopropyl alcohol with rigorous stirring at room temperature. Next, 1.6 mL of glacial acetic acid was added dropwise to the colorless solution.…”

Section: Fabrication Of Tio2 Coatings On Optical Fibers Using Sol-gel...mentioning

confidence: 99%

“…As the irreversibility of the final step is atypical for responses using this sensor design at ambient conditions, 6,7 highpressure tests were carried out by only pressurizing in a neutral solution or a basic solution. The neutral results showed evidence that while the exposure of the fiber to high pressures in neutral conditions did not cause an immediate response, depressurization caused a repeatable and irreversible increase in transmission when the solution was exchanged with a second neutral solution at ambient conditions (Figure 7) at 125 minutes and a third at 250 minutes.…”

Section: Pressure and Ph Effects On Coating Stabilitymentioning

confidence: 99%

“…4,5 We have focused on a fairly low-cost option in TiO2 as the oxide is stable against a wide range of temperatures and chemical conditions, and shows fairly consistent pH sensing behavior. [6][7][8] We have previously demonstrated that TiO2 is viable as a transmission-and backscattering-based pH sensor on the basis that it likely undergoes a change in refractive index at high pH relative to neutral pH at both high and room temperature conditions. 7 In this report we demonstrate that much of this sensing is retained at higher pressures on the order of 1000 psi, which is close to that used in some hydrogen storage conditions.…”

Section: Introductionmentioning

confidence: 99%

“…[6][7][8] We have previously demonstrated that TiO2 is viable as a transmission-and backscattering-based pH sensor on the basis that it likely undergoes a change in refractive index at high pH relative to neutral pH at both high and room temperature conditions. 7 In this report we demonstrate that much of this sensing is retained at higher pressures on the order of 1000 psi, which is close to that used in some hydrogen storage conditions. 9 Sensor testing was performed using both optical transmission and distributed backscattering measurements, with distributed measurements allowing for improved locationbased monitoring of wellbore conditions.…”

Section: Introductionmentioning

confidence: 99%

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TiO2-coated optical fibers for distributed pH monitoring at high pressures and temperatures

Shumski

Diemler

Wuenschell

et al. 2023

Optical Waveguide and Laser Sensors II

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In the oil and gas, CO2 sequestration, H2 subsurface storage, and geothermal energy sectors, subsurface pH measurements are critical for monitoring the geochemical conditions and structural integrity of wellbore systems. Real-time pH measurements in these conditions are vital for detecting and predicting corrosion deterioration of wellbore components that may jeopardize the safety and continued operation of wellbore systems. The viability of TiO2-coated optical fibers has previously been demonstrated as an effective sensor design for continuous distributed pH monitoring at elevated temperatures and ambient pressures. However, real wellbore conditions contain high pressures and the effects of high pressures on sensor results and the sensing layer have not been well studied. As TiO2 has been established in the literature as being stable at temperatures and pressures substantially higher than those expected in typical wellbore conditions, it makes for a promising sensing material for applications requiring high-pressure, high-temperature (HPHT) conditions. In this study, a sol-gel deposition method is used to coat the optical fiber sensors with TiO2 sensing layer. The sensor performance was measured using optical transmission measurements at various pH and using optical backscatter reflectometry for distributed pH sensing demonstration in wellbore-relevant pressures (up to 1000 psi) and temperatures (~80 °C). The TiO2 sensing layer was characterized using scanning electron microscopy (SEM) and full spectrum UV-Vis-NIR transmission data for a planar substrate. The TiO2-coated optical fiber sensor is tested for any pressure-derived effects and the viability of this sensor design for real-time in-situ wellbore pH monitoring is discussed.

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Section: Transmission Results Of Tio2-coated Optical Fibers For Ph Se...mentioning

confidence: 99%

Section: Fabrication Of Tio2 Coatings On Optical Fibers Using Sol-gel...mentioning

confidence: 99%

Section: Pressure and Ph Effects On Coating Stabilitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

TiO2-coated optical fibers for distributed pH monitoring at high pressures and temperatures

Shumski

Diemler

Wuenschell

et al. 2023

Optical Waveguide and Laser Sensors II

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Calcined polyethyleneimine-coated optical fibers for distributed pH monitoring at high pressures and temperatures

Shumski,

Diemler,

Wright

2024

Optical Waveguide and Laser Sensors III

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In the oil and gas, CO2 sequestration, H2 subsurface storage, and geothermal energy sectors, subsurface pH measurements are critical for monitoring the geochemical conditions and estimating potential corrosion rates of wellbore systems. Realtime pH measurements in these conditions are vital for detecting and predicting corrosion deterioration of wellbore components that may jeopardize the safety and continued operation of wellbore systems. Previous tests using metal oxidebased coatings (TiO2) provided strong responses at elevated temperatures and moderate pressure stability but provided poor differentiation between acidic and alkaline solutions. Building off the pH responsiveness of the TiO2 surface and known pH sensitivity of amine-based polymers, a coating based on the secondary amine polymer polyethyleneimine (PEI) was developed. As the polymer itself is highly water soluble and easily removed by aqueous solutions, the sensor coating was treated with a high temperature (500 °C) calcination procedure in air to convert it into a more stable oxidized coating capable of withstanding hot aqueous solutions without dissolving while retaining linear pH sensitivity from pH values between 2 and 11. The sensor performance was measured using optical transmission measurements in solutions of various pHs and using optical backscatter reflectometry for distributed pH sensing demonstration in wellbore-relevant pressures (up to 1,000 psi) and temperatures (80 °C). A calibration curve with strong differentiation between acidic and alkaline pH was developed for both transmission-based and distributed pH measurements, using fixed wavelength transmission and integrated linear amplitude of backscattered light for distributed measurements.

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TiO2 coated optical fibers for distributed real-time pH monitoring in wellbore conditions

Cited by 2 publications

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TiO2-coated optical fibers for distributed pH monitoring at high pressures and temperatures

TiO2-coated optical fibers for distributed pH monitoring at high pressures and temperatures

Calcined polyethyleneimine-coated optical fibers for distributed pH monitoring at high pressures and temperatures

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