Bellona Notat/Bellona Paper:
Carbon Dioxide Storage: Geological Security and Environmental Issues – Case Study on the Sleipner Gas Field in Norway

By Dr. Semere Solomon, The Bellona Foundation

Summary
Carbon dioxide capture and storage (CCS) is one option for mitigatining atmospheric emissions of carbon dioxide and thereby contributes in actions for stabilization of atmospheric greenhouse gas concentrations. Carbon dioxide storage in geological formations has been in practice since early 1970s. Information and experience gained from the injection and/or storage of CO2 from a large number of existing enhanced oil recovery (EOR) projects indicate that it is feasible to safely store CO2 in geological formations as a CO2 mitigation option. Industrial analogues, including underground natural gas storage projects around the world and acid gas injection projects, provide additional indications that CO2 can be safely injected and stored at well-characterized and properly managed sites. Geological storage of CO2 is in practice today beneath the North Sea, where nearly 1 MtCO2 has been successfully injected annually in the Utsira formation at the Sleipner Gas Field since 1996. The site is well characterized and the CO2 injection process was monitored using seismic methods and this provided insights into the geometrical distribution of the injected CO2. The injected CO2 will potentially be trapped geochemically pressure build up as a result of CO2 injection is unlikely to occur. Solubility and density dependence of CO2-water composition will become the controlling fluid parameters at Sleipner. The solubility trapping has the effect of eliminating the buoyant forces that drive CO2 upwards, and through time it can lead to mineral trapping, which is the most permanent and secure form of geological storage. Overall, the study at the Sleipner area demonstrates the geological security of carbon dioxide storage. The monitoring tools strengthen the verification of safe injection of CO2 in the Utsira formation. This proves that CO2 capture and storage is technically feasible and can be an effective method for greenhouse mitigation provided the site is well characterized and monitored properly.

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