A critical review of distributed fiber optic sensing for real-time monitoring geologic CO2 sequestration

Geologic CO2 sequestration (GCS) has been identified as the most viable option for effectively reducing greenhouse gases emissions to mitigate global warming and worldwide climate change. However, CO2 injection into subsurface can induce reservoir expansion and fault reactivation, which ultimately result in near-surface infrastructure damage and personnel insecurity. Distributed fiber optic sensing (DFOS) technologies function one single fiber as an array of sensors to in-situ monitor multi-parameters, such as geomechanical deformation (i.e., strain), temperature, acoustics and pressure along the entire fiber or cable length. Due to its superiority over conventional geophone and detector, DFOS tool possesses great potential to sense geofluid injection-induced small disturbances in deep subsurface. Here we begin by highlighting recent research efforts in available monitoring tools employed in GCS sites. Given the increasing attentions of optical sensing, we present a first-hand review of DFOS categories, sensing principles, and advantages for GCS related investigations from both laboratory and field scales. We discuss in detail three typical DFOS-deployed GCS projects and explore the implicit findings to guide subsequent GCS field applications. Finally, we summarize the major challenges and going forward in developing, utilizing, and extending DFOS systems to widely apply for the future large-scale all-optical GCS monitoring sites.