She is researching the future of carbon dioxide storage

“It’s extremely important to have full control over what happens to the carbon dioxide after it’s been pumped down”, says Auli Niemi.

Auli Niemi is a Professor in the Department of Earth Sciences, and along with colleagues from universities and companies around the world she is researching the future of CO2 storage. She has coordinated and had leading roles in three other major EU projects on CO2 storage and is one of the university’s most successful researchers within EU’s Seventh Framework Programme. On 27 January, she was awarded the Björkén Prize by Uppsala University.

The technique involves injecting carbon dioxide under high pressure into the porous bedrock. There the carbon dioxide can be absorbed by saline aquifers, or fill depleted oil and gas reservoirs. Around the world there are lots of abandoned oil reservoirs, but still many more deep aquifers with undrinkable salt water. These saline aquifers would be particularly suited for the large amounts of carbon dioxide storage needed.

“For CO2 storage to work, three principal requirements must be met. First, we must have a suitable geological reservoir. This could be a type of rock such as sandstone, which is porous and could contain liquids and gases – for example water, oil, natural gas or carbon dioxide. Secondly, we must have a ‘lid’, a more compact rock such as mudstone or shale, closing the reservoir upwards so that the gas is not seeping out. Thirdly, our reservoir must be at a minimum of 800 meters deep in order to secure the right pressure and temperature conditions for the carbon dioxide to enter a so-called supercritical phase, which is a hybrid between gas and liquid. If all the conditions are met, carbon dioxide can be stored long-term in the bedrock,” says Auli Niemi.

Carbon dioxide is captured

The idea is that carbon dioxide will be captured upon release in for example, coal power plants, steel mills etc., compressed and transported by pipelines or shipped to suitable storage areas where it can be pumped into the reservoir.

“We need a technically complex production chain to succeed with large-scale CO2 storage. But most parts of that chain have already been established from previous applications. We have pumped water, oil and gas out of the ground for a long time and used complex transportation systems for their distribution. You could say that this turns the process around, as we develop new applications of already-developed technologies. It’s extremely important, however, to have full control over what happens to the carbon dioxide after it has been pumped down, something that requires reliable methods to characterize storage sites and to monitor the behavior of CO2 in the reservoir. It’s the latter that’s the focus of our research.”

Testing facility in Israel

The largest of Auli Niemi's projects is MUSTANG, where she and her colleagues have built a test facility for CO2 storage and monitoring in a 1.6 km deep saline aquifer in Israel.

“When you pump down carbon dioxide in the saline aquifer, very exciting things happen! First, the carbon dioxide starts to rise, as it’s lighter than water. Along the way, some of it dissolves in the water, like in a carbonated drink. Other parts of the carbon dioxide get trapped in the pore spaces, or eventually tied chemically as new carbonate mineral. The carbon dioxide that is left is simply stopped by the cover consisting of the compact layers above the reservoir. So there are a host of different processes that occur with carbon dioxide deep down, and we’re trying to understand what’s most important, how fast these processes develop, and which may cause problems, as well as developing reliable methods to quantify and monitor these processes,” explains Auli Niemi.

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Find out more:

This year’s Björkén Prize to energy researchers

The EU project MUSTANG

Börje Dahrén