Developments since 2005 in understanding potential environmental impacts of CO2 leakage from geological storage

Highlights: • We review research since 2005 on potential impacts of leakage from CO2 storage. • We consider near surface onshore and offshore impacts and those on potable groundwaters. • Low level leakage through faults or wells is likely to be limited and recovery rapid. • Effects are reduced by mixing, dispersion and buffering. • Larger leaks are possible but less likely and should be easier to detect and remedy. Abstract: This paper reviews research into the potential environmental impacts of leakage from geological storage of CO2 since the publication of the IPCC Special Report on Carbon Dioxide Capture and Storage in 2005. Possible impacts are considered on onshore (including drinking water aquifers) and offshore ecosystems. The review does not consider direct impacts on man or other land animals from elevated atmospheric CO2 levels. Improvements in our understanding of the potential impacts have come directly from CO2 storage research but have also benefitted from studies of ocean acidification and other impacts on aquifers and onshore near surface ecosystems. Research has included observations at natural CO2 sites, laboratory and field experiments and modelling. Studies to date suggest that the impacts from many lower level fault- or well-related leakage scenarios are likely to be limited spatially and temporarily and recovery may be rapid. The effects are often ameliorated by mixing and dispersion of the leakage and by buffering and other reactions; potentially harmful elements have rarely breached drinking water guidelines. Larger releases, with potentially higher impact, would be possible from open wells or major pipeline leaks but these are of lower probability and should be easier and quicker to detect and remediate