Integrated Fixed and Mobile Devices for CCS Monitoring - Baseline Campaign Results
Authors: Bruni F. , Furlan F. , Grasso T. , Miozza L. , Filippini M. , Chomicz R. , Mori M. , Gerolin M. , Cesari C. , Murmura P. P. , Carbone P. , Argento F. , Ambrosini S. , Vignali A. 
Published: February 2025

O2 offshore storage is one of the key elements of Eni's strategy for Energy Transition, aiming at minimizing GHG industrial emissions, in particular for hard to abate sectors. The relevant storage sites need appropriate monitoring activities aimed at verifying that injection operations proceed as planned. Environmental surveys are part of these activities, with the overall objective of identifying any unexpected changes to the geophysical, physical, chemical, and biological environment and, in the unlikely case, promptly implement the appropriate corrective actions. Based on the above considerations, this paper presents an approach to monitoring for offshore CO2 storage fields, based on Eni proprietary technologies: Clean Sea for environmental and geophysical surveys using underwater autonomous vehicles and Landers (seafloor benthic stations) for continuous environmental monitoring.

The concept of CO2 offshore storage integrated monitoring system has been applied for the environmental monitoring baseline of the CCS Fase 1 project in Ravenna (Porto Corsini Mare Ovest field). Purpose of the monitoring system is the assessment of the impact on the marine environment by the possible release of CO2 resulting from the storage of carbon dioxide coming from onshore site (Eni S.p.A. Centrale gas Casalborsetti).

The first monitoring technology adopted is the well-proven Clean Sea robotic system, able to automatically execute inspection, surveys, and monitoring tasks in offshore scenarios. Clean Sea makes it possible surveys of large areas in a single mission with full coverage, providing detailed environmental maps of the areas of interest characterized by a data density not comparable with traditional techniques. The adopted monitoring strategy included the acquisition of in-situ oceanographic parameters and geophysical surveys. On the other hand, to cover the long-term monitoring at seafloor, a new concept of benthic station called Lander, equipped with state-of-the-art sensors for environmental monitoring of chemical and physical parameters of the water column, has been developed and utilized.

This work presents a description of the main results of the environmental baseline campaign performed for the CCS Fase 1 project in Ravenna using the Eni's proprietary technologies Clean Sea and Lander, pointing out the advantage of such an integrated approach for environmental monitoring.

The proposed technologies reported here contribute to an integrated and multidisciplinary approach to the problem of monitoring offshore reservoirs for CCS purposes. Various techniques were tested for monitoring offshore CCS sites. The Clean Sea AUV can detect gas leaks over large areas using acoustic measurements. A comparison between different data acquired is necessary to exclude the presence of false positives. The Lander device worked well, providing data to refine its operation. During three campaigns, measurement settings were optimized, anti-fouling strategies were tested, and mission durations were set based on seasons. The data collected matched other available information and seasonal trends. Clean Sea makes area monitoring possible with better performance (accurate mapping) and lower logistics costs compared to traditional systems while environmental benthic stations (Landers) allow continuous monitoring of pre-established critical points (e.g., near injection wells, abandoned exploration wells, pockmarks, faults or other known areas of gas seepage).