(618c) H2 Sensing with an Optical Fiber Sensor in the Subsurface H2 Storage Conditions

Hydrogen can be stored in underground gas storage reservoirs in a large quantity for the high demand foreseeable in the near future. The concentration of hydrogen is subject to change due to biological reactions in the underground reservoirs and leakage through caprocks. Thus, monitoring hydrogen concentration in the subsurface gas storage deposits is vital to ensure the integrity and safety of the storage facilities. An optical fiber sensor is the most suitable sensing platform for the underground gas storage environments with the unique advantages of real-time and remote sensing without a risk of ignition and explosion. However, the optical fiber hydrogen sensor is not fully developed and validated for deployment under the harsh environment expected in underground gas deposits. In this study, the optical fiber hydrogen sensor was coated with a Pd/SiO2 layer and a filter layer, which enables H2 sensing in relevant subsurface storage environments. Specifically, the sensor has demonstrated successful sensing performance at high temperatures (~80 °C) and high pressures (~1,000 psi) under very humid conditions (~100% RH). In addition, the sensor was exposed to real subsurface microbial samples in the harsh environments described above to monitor microbially induced changes in hydrogen concentration. The sensor has shown stable H2 sensing responses in the replicated underground hydrogen storage conditions without deterioration or loss of H2 sensitivity. In addition, the biological subsurface sample with hydrogen gas resulted in higher transmission intensity change than the abiotic subsurface sample due to the possible hydrogen consumption with microbes. The successful demonstration of H2 sensing in relevant underground gas storage conditions would increase the readiness for deployment of optical fiber H2 sensors into the subsurface hydrogen storage reservoirs.