**1. Introduction**

Carbon Capture and Storage (CCS) is a method to reduce anthropogenic greenhouse gas emissions thereby mitigating global warming. In CCS, carbon dioxide (CO2) is captured from fossil fuel-fired power plants or other large point-source emitters, purified, compressed and injected deep underground into subsurface formations at depths of or greater than 800m. At such depths CO2 is in a supercritical (sc) state increasing storage capacity (IPCC 2005).

In CCS, there are four main mechanisms which keep the buoyant CO2 underground:


The focus of this text is on dissolution trapping; how much CO2 dissolves under which geothermal conditions and what happens to the CO2-enriched brine, which is slightly denser than the original formation brine, in the formation.

Important open questions in this context are: How fast are these mass transfer processes in real geological porous media under realistic CCS conditions? Are there means of accelerating CO2 dissolution? How do separate gas and/or oil phases (oil and/or gas reservoirs) in the reservoir affect CO2 dissolution processes and reservoir fluid dynamics? How does the pressure drop due to CO2 dissolution affect injectivity and storage capacity of CO2?
