Leakage risk assessment of a CO2 storage site: A review

Carbon Capture and Storage (CCS) has been widely recognized as an effective strategy that may significantly contribute to achieving the net zero emission target by 2050. There are currently more than 50 CCS injection and pilot sites around the globe that may require a long-term integrity assessment to avoid leakages or contamination of subsurface resources. The major concern here is the complex interactions of CO2 with rocks and other sealing materials (cement) that can be accelerated by pressure and temperature conditions. In this paper, we review different mechanisms that may lead to the generation of leakage paths in CO2 geological sites and attempt to provide a risk assessment scheme that may improve the safety of injection and storage operations. It seems that the results reported from the laboratory experiments are still inconclusive and not comparable with the field observations. This could be due to the limited duration of the tests conducted, complexity of mechanisms involved and the slow reaction rates of many chemical processes in a CO2 storage site. Geochemical reactions, pressure and temperature are the main parameters that can potentially induce leakages from different geological sites, but a poor cement job is perhaps the main reason behind the leakage of CO2 from the near wellbore region during injection and storage.