Storage of CO2
Geological CO2 Storage is Feasible...
Large natural deposits of CO2 exist in bedrock formations in many places
on Earth. It is therefore an obvious solution to apply the same approach
to limiting the amount of anthropogenic CO2 emissions to the atmosphere.
Norway has been applying this method of CO2 storage under the North Sea
for more than 10 years. It is important that the geological formations used
for storage are suitable so that the stored CO2 does not escape. Deeply buried porous rock formations sealed by overlaying thick and impermeable rocks are suitable storage formations.
How it’s done
To get an idea of how a rock formation can store large amounts of CO2, fi ll a glass with sand. Then pour water over the sand. You will see that even though the glass is filled with sand, the glass will still accommodate water equivalent to about 20-30% of its volume. Underground sandstone formations are imilarly filled with water, and this water can be replaced with CO2. CO2 can be separated from power plant or other industrial emissions, and then transported by ship or piped to the storage site on the continental shelf. Here, an approximately 1 km deep well is drilled into the seabed.
The carbon dioxide is converted to its fluid form under high pressure and then injected into the aquifer. The storage formations must be continuously monitored in order to ensure that the CO2 does not escape.
Experience from the Sleipner field
In 1996, Statoil started using this method to store CO2 on the Sleipner natural gas field. The method was initially developed because the Sleipner gas contained more CO2 than allowed by the European gas market. Statoil had to remove some of the carbon dioxide, and would have had to pay an environmental tax if the surplus CO2 was emitted to the atmosphere. CO2 capture is performed directly on the North Sea platform. Concentrated CO2 is then pumped via a well into the Utsira formationabout 1 km below the seabed. Annually, about one million tonnes of CO2 are stored in the Utsira formation. Follow-up studies have shown that the storage has been successful, as no leakage whatsoever has been observed so far.