Case study: Offshore CCS – carbonated water injection

Alternative solutions to deposit CO2 captured from gas turbine power plants on offshore petroleum production platforms have been analysed. The following alternatives were considered: 1. Dissolution of CO2 in sea water and aquifer storage of carbonated water 2. Injection of pure CO2 into an aquifer 3. Compression of CO2 and pipeline transport to a collection centre 4. Liquefaction of CO2 and ship transport to a collection centre 5. Dissolution of CO2 in sea water and injection into oil fields (carbonated water injection, CWI) For carbonated water injection both into green and brown fields were considered, using both heterogeneous and homogeneous field models. Incremental oil productions and CO2 retention were estimated for the various cases. For each alternative the investment costs and operating costs were estimated and the NPV for each alternative was determined. Credit for saved CO2 tax was included as incomes. Alternatives 1 – 4 have negative net present values. All cases related to Alternative 5 (project lifetime, heterogeneous and homogeneous reservoir models, green and brown fields) exhibit positive net present values due to incremental oil production. Most, but not all, injected CO2 remained in the reservoir.