Mediterranean Casablanca-DAS seafloor fibre optics: from geoscience to real time offshore monitoring

Offshore decommissioning of oil and gas platforms, once fields have completed their productive life, presents several impacts—primarily economic and environmental. However, these impacts can be mitigated, offering both challenges and opportunities (win-win). It is worth noting that offshore platforms, close to the coast, concentrate dense maritime traffic, are prone to environmental, geohazards & subsurface monitoring; not forgetting that they are usually located in strategic areas.

Casablanca platform (offshore Mediterranean, REPSOL operator & CLMV-MOEVE-NATURGY partners) has been operated for more than 40 years until 2021. Located in the continent shelf off Tarragona (Spain), its area is nearby a major Mediterranean port, active fishing grounds, intense surface-wave & storms and presence of a known migration corridor for marine mammals. This infrastructure represents a real opportunity for long-term observations, specifically in an offshore region (> 160 meters water-depth)  were natural, anthropogenic, geophysical and biological processes converge periodically.

Last year a submarine fiber-optics cable (Distributed Acoustic Sensing DAS) was deployed in Casablanca platform; with real time data since Q4-2025. This project was carried out under the European Union Next Generation EU in a public-private collaboration between ICM-CSIC, REPSOL, Alcalá University and Aragon Photonics. By transforming submarine optical fiber cable into dense arrays of virtual sensors, this pilot project enables continuous monitoring of physical processes across solid earth, water column not forgetting atmosphere -ocean interface over displayed cable length of seafloor. But this is not just data acquisition, there is a further paramount computing potential ahead. Artificial Intelligence (AI) has been implemented to tailor DAS data to detect and also classify, almost automatically existing signals from several physical domains. In this case after conditioning & denoising it is possible to differentiate seismic events, vessel activity, marine mammals, ocean-wave and infrastructure related noise; among others. Data Analysis supported by artificial intelligence has proved quite useful, at first sight, for continuous offshore monitoring, detection of low magnitude seismic events.

First results, even still provisional, are quite promising and reveal further potential of fiber-optics sensing based on additional cable deployment and focused seafloor design. These real capabilities, not just hypothetical studies,  would visualize Casablanca platform as a host scientific observatory for offshore seismicity, ocean noise maritime traffic and possible geohazards, among others. This is a potential step (with real insights) to visualize sustainable & useful future for a legacy asset. A second phase study is already in motion, through a scalable pathway; so, this project just moved from geoscience to real time offshore monitoring. More results to come, stay tuned.