How to store carbon dioxide deep underground

CO2 emitted from fossil fuels is widely recognised as one of the main drivers of climate change. Technologies that sequester CO2 from sources like power plants and oil refineries could substantially reduce CO2 emissions into the atmosphere.

Carbon capture and storage (CCS), where waste CO2 is captured from its source and stored underground, is a promising way to reduce atmospheric CO2. Little is known, however, about the long-term impacts of storing CO2 over geological time spans.

The EU-funded PANACEA (Predicting and monitoring the long-term behavior of CO2 injected in deep geological formations) initiative used computer modelling and natural case studies to establish whether CO2 injected into deep geological formations can be stored effectively and safely.

To understand and predict the long-term fate of the stored CO2, researchers simulated the behaviour of CO2 in different geological formations. These included deep-seated saline aquifers and various natural geological reservoirs.

The team then used field data and rock samples to analyse how CO2 will affect the rocks and minerals it interacts with during storage. Importantly, they identified the main factors that result in CO2 leaking out of the reservoirs, and provided measures for preventing such leakage into the atmosphere.

Other simulations evaluated the mechanical impacts of, for example, pressure build-up. They also simulated the stability of stored CO2 over 3 000 years and estimated the amount of CO2 that leaked to the surface during that time.

Accurate and reliable models showing which features of CO2 storage are effective and safe, and which should be avoided, should improve confidence in this technology. In addition, monitoring techniques developed during this project will be extremely useful for regulators and future developers of CCS sites.