Hollow-core photonics crystal fiber for CO2 leakage monitoring

Robust monitoring at a carbon capture and storage (CCS) site to detect, locate, and quantify CO2 migration is necessary for providing early warning for an approaching well failure and potential gas leaking. We report on distribute chemical sensing via Raman spectroscopy in hollow core fibers (HoF) for direct gas detection via the percolation of gas into the fiber open core, leading to larger matter-light interaction and thus amplification of Raman signal. We present our experimental results on Raman detection in terms of concentration and uptake time for various HoF lengths with and without side microchannels. Guided by numerical studies, the optimized number of side holes lasers to possibly augment CO2 penetration rate into the air-filled core was determined and channels were drilled with pulsed femtoseconds Ti-Sa laser. We also investigated splicing open joint collars for integrating HoFs with solid core fibers (SCFs), critical in any deep or large surface area coverage deployment, and fiber Bragg gratings (FBGs), valuable in enhancing SNR via backscattering while generating time-space signal mapping and temperature/pressure sensing for baselining. By interleaving HOFs, FBG and SCFs, the optical spectroscopy methodology could offer a path to overcome current roadblocks to gas storage wells, as specialized fiber optics will allow direct detection of gases, in wells with in-situ and low power measurements of concentration.