Optical Fiber: When the Heat and Pressure Are On
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Many land and oceanic oil operations use temperature sensing to help improve safety and functionality in harsh environments. Optical fibers used in these conditions are routinely exposed to high temperatures and pressures, along with ionizing radiation and aggressive chemicals in the surroundings.
Given these extremes, companies are increasingly using silica-based optical fibers for both acoustic and distributed temperature sensing. These fibers offer advanced properties including superior thermal stability and mechanical robustness. They are also able to transmit optical power with minimal added attenuation or signal loss.
While researchers have thoroughly studied the mechanical strength of optical fibers under ambient conditions, they have rarely examined fibers after exposure to elevated temperatures and/or liquids. In fact, to the best of our knowledge, there is no systematic data documenting the mechanical strength of optical fibers placed under high temperatures and pressures such as those experienced in temperature sensing.
That’s why when Andrei Stolov of OFS decided to perform an experimental study, he was operating in somewhat “unknown territory.” Before beginning the experiment, Stolov realized that a number of factors would influence whether optical fibers could survive the harsh conditions found in oil operations. These aspects include the type of fiber coating, environment, temperature, pressure and usage time.
When optical fibers are used at elevated temperatures or in aggressive environments, the most frequent indications of failure are added attenuation or loss of mechanical strength. In Stolov’s study, he used strength degradation as his criteria for failure.
In his experiment, Stolov submerged a range of optical fibers with various coatings into four high-temperature/high-pressure fluids, namely (1) distilled water; (2) sea water; (3) isopropyl alcohol (IPA); and (4) paraffin oil. Undersea and downhole applications primarily drove his choice of fluids. In these situations, fibers can be exposed to these or similar environments.
To learn more about the study and the results, please go HERE.