Initial observations from testing surface fiber optics aimed at onshore CCS monitoring in Denmark

Abstract Onshore carbon capture and storage (CCS) projects require cost-effective and reliable monitoring solutions to ensure conformance and containment of the injected CO2. Distributed Acoustic Sensing (DAS) using fiber-optic cables has emerged as a promising technology, but its performance in surface deployments onshore remains unclear. We present initial observations from a controlled experiment near the Kalundborg CCS license area in Denmark, designed to evaluate DAS data quality from two fiber configurations: an existing telecommunication cable and a dedicated trenched cable. Both active-source and passive recordings were acquired, complemented by nodal geophones for comparison. Preliminary results show that repeatable signals from Vibroseis sweeps can be detected on both fibers, although cultural noise significantly influences data quality. The dedicated fiber exhibited clearer signal structure and lower noise levels than the existing cable. The findings highlight key challenges faced for operational deployment, including noise mitigation, coupling stability, and how to integrate the fiber optics in interpretation strategies. Further analysis of the full dataset, including passive recordings, will aim to inform recommendations for integrating surface fiber optics into onshore CCS monitoring frameworks.