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New study highlights role of subsurface saline aquifers in safe and secure CO2 storage
A new study by scientists from Scotland and Malaysia has provided insights into the role of natural mechanisms within rocks deep below ground for securely storing anthropogenic carbon dioxide (CO2).
The team from the University of Edinburgh and Universiti Teknologi Petronas carried out a comprehensive review of past, recent and ongoing developments in CO2 storage in saline aquifers. Their findings have boosted understanding of how different trapping methods can maximise the security and storage potential of any CO2 storage site, which will be of value to countries seeking to develop carbon capture and storage (CCS) projects.
CCS technology, if delivered at scale alongside other measures, can substantially reduce society’s carbon emissions from different sectors, such as industry and power generation, and help tackle climate change.
The researchers studied the different ways that CO2 can become trapped within the pore space of rocks of aquifers considered ideal for carbon storage. The CO2, once captured and injected into these saline reservoirs, will displace saline water and take its place within the tiny gaps between rock grains. An overlying cap rock, which is impermeable to fluids, will then provide a permanent seal. The greenhouse gas (GHG) can also dissolve within the reservoir fluid – a mechanism known as solubility trapping – and, over a long period of time, can react with the rock and saline water to form new minerals, resulting in geochemical trapping. In addition, as CO2 flows through the storage rock, some can become separated from the main flow and get left behind as disconnected droplets. This is known as residual trapping.
Dr Katriona Edlmann, Chancellor’s Fellow in Energy at the University of Edinburgh says: ‘Our research provides further evidence that captured CO2 emissions can be stored securely for thousands of years in rocks deep underground. Commercial-scale CCS as part of a global transition to net zero carbon is moving even closer. Within the UK, that includes the establishment of the net zero carbon industrial cluster in the Humber and the Acorn CCS project at St Fergus in north-east Scotland.’
Dr Jalal Foroozesh, Senior Lecturer in Chemical Engineering Department and Research Member in Institute of Hydrocarbon Recovery at Universiti Teknologi Petronas, adds: ‘With real concern currently on the global warming issue due to CO2 as one of the main greenhouse gases, subsurface CO2 storage as a part of CCS technology offers a practical solution to reducing the concentration of anthropogenic CO2 in the atmosphere. Although other subsurface geological formations, such as depleted hydrocarbon reservoirs, are available for underground trapping of CO2, saline aquifers have attracted more attention due to their large storage capacities and rock properties that allow high injectivity of CO2. Our review summarises the key technical and economic parts of CO2 storage projects in subsurface aquifers that can help engineers and scientists with better planning and designing, and also assist managers in making better business decisions on such projects.’