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

Alexander Shumski; Nathan Diemler; Ruishu Wright

doi:10.1117/12.3013421

7 June 2024 Calcined polyethyleneimine-coated optical fibers for distributed pH monitoring at high pressures and temperatures

Alexander Shumski, Nathan Diemler, Ruishu Wright

Author Affiliations +

Proceedings Volume 13044, Optical Waveguide and Laser Sensors III; 130440L (2024) https://doi.org/10.1117/12.3013421
Event: SPIE Defense + Commercial Sensing, 2024, National Harbor, Maryland, United States

Abstract

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. 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. Previous tests using metal oxide-based 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 1,000psi) 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.

Conference Presentation

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

Citation Download Citation

Alexander Shumski, Nathan Diemler, and Ruishu Wright "Calcined polyethyleneimine-coated optical fibers for distributed pH monitoring at high pressures and temperatures", Proc. SPIE 13044, Optical Waveguide and Laser Sensors III, 130440L (7 June 2024); https://doi.org/10.1117/12.3013421

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