CO2 moves upwards to the top seal. Over time the CO2 dissolves into the formation water. This makes it denser and it moves downwards.
Carbon dioxide can be injected into oil reservoirs, making the oil easier to produce. Some of the carbon dioxide remains trapped in the rocks.
Carbon dioxide can be reacted with minerals to form stable carbonates. The mineral needs to be crushed and research is underway to increase the rate of reaction.
CO2 can be stored in mineral residues such as red muds produced by alumina refineries.