8.1 Introduction

Injection of CO2 into sandstones of the Utsira Formation in the North Sea began in 1996 as part of Statoil’s Sleipner Project which has now stored over 13 Mt CO2. In Algeria, the In Salah Gas Project has been injecting CO2 into the Krechba Formation since 2004 with over 4 Mt CO2 stored. These projects have used a wide range of monitoring techniques and have demonstrated that it is possible to safely manage the injection of CO2 into geologic reservoirs. Oil companies have been injecting CO2 into ageing oil fields to enhance the recovery of oil (CO2 EOR) since the 1970s, and there are now more than 130 such operations, mainly in North America. Most companies, for economic reasons, recycle the injected CO2 which results in the CO2 being effectively stored permanently within the oil reservoir. The Weyburn Oil Field in Saskatchewan, Canada, for example, has now stored in excess of 18 Mt CO2. Thus the technologies and operational aspects of injecting and storing CO2 in geologic formations are established processes. Storing CO2 captured from industrial processes in geologic formations is also the component in the CCS chain that presents some of the greatest project challenges. Each geologic storage site is unique and must be screened and extensively characterised, taking years and millions of dollars before a decision can be made to proceed with a commercial project. Geologic storage can also represent the most important public perception challenge and the greatest long-term financial liability associated with a CCS project.