GEUS has been studying the possibilities of geological storage of CO₂ for many years and has participated in international networks to strengthen Europe's scientific and technological position in the field. The work covers the entire value chain from capture through transport to storage, but our focus is on providing knowledge about the geological conditions and how CO₂ is stored underground.
To store CO₂, suitable geological formations in the subsurface are needed. The reservoir for CO2 should be at a depth of at least 800 meters and consist of porous geological layers, such as sandstone or limestone. To ensure that CO₂ does not migrate upward and escape into the atmosphere, the reservoir must be sealed by a tight layer, such as mudstone. Geological storage of CO₂ is a technique that has been used for decades and is already occurring in many places around the world, for example in the North Sea. In the Danish subsurface, there are several suitable formations that can accommodate large amounts of CO₂.
How GEUS calculates storage potential
GEUS prepares static estimates of Denmark’s CO₂ storage potential. These are theoretical calculations that show how much CO₂ the subsurface can hold based on geological data such as porosity, thickness and area. This method makes it possible to compare the storage potential between countries on a uniform basis – in the same way that the oil and gas industry uses resource estimates to assess how much oil and gas can be found underground before drilling.
The dynamic estimates are prepared by the storage operators when specific structures need to be investigated. Detailed data and reservoir simulations are used to calculate how much CO₂ can actually be stored safely, taking into account pressure conditions, well location and operating conditions. This corresponds to the oil industry’s reserve estimates, which focus on how much can actually be extracted.
So, GEUS’ static estimates provide an overall picture of Denmark’s geological potential, while the dynamic calculations show how much of this potential can be exploited in practice. The estimates are continuously updated as new knowledge and data about the subsurface become available.
GEUS has a particular focus on the safety aspects of CO₂ storage, including which monitoring methods can be used to map the migration of the CO₂ plume in the subsurface and ensure that potential leaks can be detected and prevented.
New data for CO₂ storage
In recent years, GEUS has conducted extensive work to map the potential for CO₂ storage in the Danish subsurface. Denmark's CCS strategy from 2021 included funding for studies of relevant and potential storage sites in the Danish subsurface, with close involvement of relevant municipalities, citizens, etc. In 2022-2024, GEUS conducted early investigations of eight areas in Denmark that are potentially suitable for CO₂ storage. In connection with the studies, new seismic data were collected, which are used to map the deeper geological structures in the subsurface.
See the list of available data here.
This is how CO₂ is stored underground