Monitoring techniques of a natural analogue for sub-seabed CO2 leakages

Carbon dioxide sequestration in sub-seafloor aims to store CO2 inside geological trapping structures below the seafloor. However there are concerns related to the possibility of leakage from the storage sites and potential consequences on the marine environment.In order to develop safe and reliable methods for CO2 monitoring, field studies were conducted in a natural analogue–an area where there is a natural release of CO2 from the seafloor.Due to the very high volume of gas emitted, this natural analogue could be considered as the worst-case scenario for a possible leakage from a sub-seabed storage site.Sampling procedures for free and dissolved gas and measuring techniques of the main physical and chemical parameters were developed for use both from the surface and directly underwater by scientific scuba divers. The first results of the research indicate that high levels of CO2 released in the marine realm strongly affect the local environmental conditions with a generalized acidification of the seawater.The experience gained in this study allows further development of a more accurate and suitable monitoring suite that will integrate sensors for measuring pH, dissolved CO2, and eventually, acoustic systems for the detection, monitoring and quantification of gas bubbles. The monitoring system could be deployed on the seafloor for long-term monitoring or could be carried onboard movable platforms such as ROV’s (Remote Operated Vehicles) or AUV’s (Autonomous Underwater Vehicles) for systematic surveys of the sub-seabed storage areas