**10. Nomenclature**


example, flow in the reservoir is strongly influenced by changes in rock morphology and wettability, which can result in changes of relative permeabilites and capillary pressures of CO2 and brine. Relative permeability and capillary pressures however strongly influence multi-phase fluid flow in the reservoir. As an example, there is evidence that wettability (Espinoza and Santamaria 2010, Chiquet et al. 2007) and rock pore morphology – especially carbonates (Luquot and Gouze 2009) are changed by scCO2. More research work is required in this area to completely understand these changes and improve CCS risk assessment.

In summary it is clear that dissolution trapping is a potential solution for storing large quantities of anthropogenic CO2 thereby reducing carbon emissions. More research is required, especially field testing with integrated monitoring to check how the CO2 behaves under realistic injection and reservoir conditions in the medium-to-long term. The major advantages of dissolution trapping are that very substantial amounts of CO2 can be stored very safely. The risk is that CO2 dissolves too slowly so that a significant part of CO2 is still in a mobile separate supercritical phase (separated from the brine phase) which is buoyant and could escape to the surface. There are however two other CCS mechanisms, structural and residual trapping which prevent or at least reduce the CO2 leakage risk. It must also be guaranteed that no drinkable-water aquifers are contaminated with CO2 or any harmful species mobilized by CO2 injection (e.g. dissolution of heavy metal ions by the acidic brine

I would like to thank Prof. Martin Blunt, Prof. Tetsuya Suekane, Dr. Amer Syed and Prof. Abbas Firoozabadi for reviewing this book chapter and helpful comments. Many thanks go

generated), which may then be transported into drinking water reservoirs.

to Prof. Zhenhao Duan for supplying the CO2 solubility calculator software.

CCS carbon capture and storage (of carbon dioxide)

<sup>−</sup> hydrogen carbonate anion

H domain depth; reservoir height [m]

D diffusion coefficient [m2/s]

**8. Conclusions** 

**9. Acknowledgements** 

**10. Nomenclature** 

H<sup>+</sup> proton HC hydrocarbon

φ porosity [-] K permeability [m2] M molar mass [g/mol] μ viscosity [Pa.s] ρCO2 CO2 density [kg/m3] GOR gas-oil ratio [m3/m3]

a year

HCO3

<sup>2</sup> CO3

CO2 carbon dioxide

<sup>−</sup> carbonate anion

Gt Gigatons = <sup>9</sup> 10 tons

