Why do we want to store carbon dioxide underground?
Natural geological systems hold buoyant fluids such as oil for
millions of years, so we have confidence that underground
storage will work.
What is a saline aquifer?
A porous and permeable rock naturally filled with salty water
What is a trap?
A structure in the rock that the carbon dioxide gets trapped in
Why do mudstones (or shales) make good seal rocks?
The carbon dioxide will be trapped below them, effectively
permanently
Why do we need mechanisms to trap the carbon dioxide
underground?
Because carbon dioxide is buoyant, and will rise back to the
surface unless something stops it.