Health, Safety and Environmental Risks of Underground CO2 Storage. Overview of Mechanisms and Current Knowledge

CO2 capture and storage (CCS) in geological reservoirs may be part of a strategy to reduce global anthropogenic CO2 emissions. Insight in the risks associated with underground CO2 storage is needed to ensure that it can be applied as safe and effective greenhouse mitigation option. This paper aims to give an overview of the current (gaps in) knowledge of risks associated with underground CO2 storage and research areas that need to be addressed to increase our understanding in those risks. Risks caused by a failure in surface installations are understood and can be minimised by risk abatement technologies and safety measures. The risks caused by underground CO2 storage (CO2 and CH4 leakage, seismicity, ground movement and brine displacement) are less well understood. Main R and D objective is to determine the processes controlling leakage through/along wells, faults and fractures to assess leakage rates and to assess the effects on (marine) ecosystems. Although R and D activities currently being undertaken are working on these issues, it is expected that further demonstration projects and experimental work is needed to provide data for more thorough risk assessment