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Session: Filling the Data Gap: Ocean-bottom Sensing with Fiber-optic Cables [Poster]

Type: Poster

Date: 10/9/2024

Time: 07:00 AM

Room: Stanley Park Ballroom

Advanced Monitoring Techniques for Mitigating Induced Seismicity in Offshore Subsurface Energy Projects: A Case Study from the CASTOR Gas Storage Site

The scientific evidence of climate change has led to new energy policies aiming for a carbon-neutral economy by mid-century. Renewable energies, energy storage systems, and carbon footprint reduction are crucial for these goals. Subsurface fluid injection is common in these projects, including green hydrogen storage in salt caverns and CO₂ storage in porous rock formations. Offshore geothermal energy production also involves deep underground water injection. Induced seismicity is a global concern in fluid injection projects, necessitating risk assessments for future operations. Fluid injection changes crustal stress, generating earthquakes whose frequency and magnitude vary with the injection rate. Long-term monitoring plans are essential for these multi-decadal, capital-intensive projects. Mitigating induced seismicity involves addressing four major issues: studying natural seismicity to evaluate fault activity, preventing injection-triggered faults, ensuring underground storage integrity, and managing moderate induced seismicity to prevent social alarm. Offshore storage sites, though challenging for seismic monitoring, reduce risks by being far from populated areas.

Effective monitoring integrates optical fiber cables with Distributed Acoustic Sensing (DAS) systems and AI algorithms for seismic detection, analysis, and location. This technology provides high-density seismological records, being an unparalleled tool to unravel the active tectonics of a target region. This approach was tested at the CASTOR offshore gas storage site, where significant induced seismicity occurred in 2013 due to gas injection. The facility, now in a phase of hibernation, was monitored for three months in 2023 using DAS on a telecom fiber optic cable connecting the offshore platform with the land facility. We recorded and located low-magnitude earthquakes under the platform, undetected by the national seismic network. This successful implementation highlights the potential of advanced monitoring technologies in ensuring the safety and viability of critical energy projects.

Presenting Author: Arantza

Additional Authors