Optical fiber evanescent-wave sensing technology of hydrogen sulfide gas concentration in oil and gas fields

For the problems of light source fluctuation noises, zero drift and other problems of H2S gas concentration sensor in optic-fiber evanescent-wave absorption spectroscopy, double-light-path absorption system was designed to theoretically analyze the relationship between evanescent-wave power and gas concentration as well as detection sensitivity. Moreover, the relationship between evanescent-wave power and optical-fiber residual diameter in the optic fiber corrosion process was also studied. The sensing probes with different evanescent-wave power ratios were used to detect experiments of H2S gas concentration. The experimental results show that the sensitivity is up to 0.169 mu w/ppm when the evanescent-wave power ratio of sensing probe is 10%, detected minimum H2S gas concentration is 5.1 ppm, the detection repeatability is good and the response time is only 2.03s. Due to low production cost, high sensitivity and short response time, the optic-fiber evanescent-wave sensor can be used for real-time on-line measurement of H2S gas in the area of the hydrocarbon exploration and development. (C) 2017 Elsevier GmbH. All rights reserved.