Injecting billions of tons of atmospheric carbon dioxide (CO2) underground contains low risk of leaking back to the surface.
According to the simulations, carbon dioxide would remain deep in the Earth’s interior for millions of years, even if the upper, low-permeability rocks were fractured.
These findings indicate that this technology, called CO2 geostorage, can be safely used to mitigate climate change.
Calculate the potential for carbon dioxide leakage
The study was carried out by the Institute for Environmental Assessment and Water Research (IDAEA) and the Mediterranean Institute for Advanced Studies (IMEDEA CSIC-UIB), both of which are affiliated with the Spanish National Research Council (CSIC).
The study, published in the journal Geophysical Research Letters, is in collaboration with Lawrence Berkeley National Laboratory and the University of Illinois at Urbana-Champaign.
This interdisciplinary research developed a new methodology for calculating the potential for CO2 leakage taking into account the billion tons of CO2 injected underground over a timescale of millions of years, which is much larger than what has been investigated so far.
“The goal of carbon dioxide storage is to take this greenhouse gas from industry that is difficult to mitigate and inject it deep into the ground, and in order for the gas to remain in the depths, it must be injected into rocks that are highly permeable and porous,” explains Eman Rahimzadeh Kaifi, IDAEA-CSIC researcher and first author of the study. Like sandstones, there is a risk of carbon dioxide seepage, as the carbon dioxide is less dense than the salt water that fills the pores very deeply, so it can float up and seep back to the surface.”
gas flows to the surface
To calculate the risk of CO2 leakage, the researchers projected the flow of gas to the surface after injection at a depth of 1,550 meters (the combined depth of underground gas storage) using numerical transport models in two different scenarios.
“Our predictions show that in the best-case scenario, when the properties of underground rocks remain intact, CO2 will only rise 200 meters upwards after a million years, in our worst-case scenario,” explains Victor Villaraca, researcher at IMEDEA-CSIC-UIB and lead author of the study. , when the rocks represent a large number of fractures that carbon dioxide will rise to 300 meters.”
“This means that even in the worst possible scenario, carbon dioxide will be contained indefinitely in the Earth’s interior at a depth of 1,250 meters for millions of years,” says Rahimzadeh Keifi.
The authors highlight that this study is relevant to increasing confidence in the security of underground carbon dioxide storage to achieve carbon neutrality and mitigate the effects of the climate emergency.
“The scenarios proposed by the Intergovernmental Panel on Climate Change (IPCC) to achieve zero emissions, and even net removal of carbon from the atmosphere, require geological storage of carbon dioxide, and this study shows that permanent storage of carbon dioxide can be safely achieved,” concludes Villarrassa.
