Long term coupled transport and geochemical modelling of the impact of CO_2 storage on the Utsira reservoir and its cap rock at Sleipner (North Sea)

摘要

Long term coupled transport and geochemical modelling is the key to understanding the long term geochemical impact of CO_2 storage. Using three different models (GEM-GHG, PHREEQC and TOUGHREACT) both the geochemical interactions as well as their impact on host rock porosity was assessed for the Nordland Shale cap rock and the Utsira reservoir over thousands of years. Results indicate that in the Utsira case geochemical reactions, other than dissolution of CO_2 and pH change, are unlikely to play a mayor role due to its low reservoir temperature (37°C) leading to very slow reaction kinetics and its little reactive mineralogy. The power of using coupled modelling is clearly demonstrated along with the uncertainties involved in especially the parameterisation of the geochemical system.