Developing Offshore CO₂ Monitoring Capabilities for CCS: Environmental Test Campaign at a Natural Venting Site in Panarea

Carbon capture and storage (CCS) is a decarbonization process which is receiving increasing attention as an efficient solution to reduce industrial emissions, especially those from hard to abate sectors. As a consequence of the increasing public and private support, the number of new CCS projects worldwide is growing at a rapid pace, leading to the need to identify new suitable storage sites. Many of these future CO₂ storage sites are planned in offshore areas, especially in Europe, which is paving the way forward to becoming one of the leaders in CCS deployment. As part of the measures needed to ensure the permanent storage of captured CO₂, a robust monitoring program of the storage sites must be established including environmental surveys to detect the extremely unlikely occurrence of subsea releases of stored CO₂.

Since 2015, Eni has developed and successfully deployed an autonomous underwater vehicle (AUV) platform called Clean Sea. Clean Sea was originally designed for upstream asset integrity activities and environmental monitoring and is now in the process of having its capabilities extended for environmental monitoring in offshore CCS projects. To validate this advancement in capabilities, an experimental survey was performed together with the National Institute of Oceanography and Applied Geophysics (OGS) at a site offshore Panarea Island, Italy. The sea around the island of Panarea is characterized by the presence of continuous emissions of CO₂ rich volcanic fluids from the seafloor. OGS manages a permanent research infrastructure, the ECCSEL NatLab Italy, at Panarea, that is one of the Italian components of ECCSEL (European Carbon dioxide Capture and Storage Laboratory infrastructure) available to the national and international scientific and industrial communities involved in CCUS related research. This natural laboratory with active CO₂ venting from the seafloor is ideal for testing the CO₂ monitoring capabilities of the Clean Sea.

A six-day experimental survey was conducted in Panarea in September 2022. During this survey, the full suite of techniques to identify the presence of CO₂ in the water column with Clean Sea was tested. This included acoustic measurements, high-definition camera observations, real-time monitoring (e.g., pH and pCO₂) of chemical water parameters, and water sampling. The campaign has shown that the selected techniques are able to clearly detect the presence of CO₂ over ambient conditions in the water column that can be attributed to gas leaks. The results obtained and lessons learned are being used to refine current capabilities and add complementary methods, where needed, overall enhancing the future monitoring program.