Varying the rate at which carbon dioxide (CO₂) is injected into geological storage sites can enhance not just their efficiency but also their ability to store the greenhouse gas securely, according to a new study.
These findings will be invaluable to developers of carbon capture and storage (CCS) projects in the UK and abroad, where varying injection rates and interruptions are expected to occur over a project’s lifespan due to, for example, CO₂ delivery rates from capture sites, pressure management and well maintenance.
The study by scientists at the University of Edinburgh suggests that, with every change or interruption to CO₂ injection into a geological storage site:
- storage security would be enhanced because interruptions have the effect of increasing the amount of CO₂ trapped within the pore spaces of the rock;
- the efficiency of storage is increased because trapped CO₂ is less mobile than free flowing CO₂ and so its migration within the reservoir is more contained;
- injection pressure would rise due to the increasingly trapped CO₂ acting as a barrier to flow and this effect would need to be managed by storage site operators.
The researchers used rock samples to simulate the injection of CO₂ and water into geological stores, creating numerical models which were then compared to a real-life, small-scale injection project at Otway in Australia.
As a CCS industry in the UK moves closer to reality, studies such as these illustrate just how the technology will work in practice and provide important data to guide development.
Dr Katriona Edlmann, Chancellor’s Fellow in Energy at the University of Edinburgh said:
It was great to see the commitment of the UK and Scottish governments at the turn of the year on the ambition to deploy CCS. With projects in the UK inching towards design studies, our findings can feed into that development. Naturally, greater efficiency brings cost reductions, and this will be welcome news for CCS project developers. We studied both in the lab and in the field to analyse what injection might look like at scale, specifically when injection rates and flow change over time. What we found was that security of storage is increased but so does pressure, and this will require suitable management.
Gareth Johnson, Research Associate with SCCS and University of Edinburgh at the time of the study, said:
It was great to compare and validate our experimental and modelling studies against real-life injection studies at the Otway site in Australia. Climate change is a global problem and collaboration with international colleagues is really important to further CO₂ storage, and we thank CO2CRC for providing the Otway data.
The paper Cyclic CO2 – H2O injection and residual trapping: Implications for CO2 injection efficiency and storage security by Katriona Edlmann, Sofi Hinchliffe, Niklas Heinemann, Gareth Johnson and Chris McDermott from the University of Edinburgh and Jonathan Ennis-King from CSIRO, Otway is published in the International Journal of Greenhouse Gas Control, January 2019.
The University of Edinburgh is one of the founding partners of the Scottish Carbon Capture & Storage (SCCS) research partnership.
|Katriona Edlmann describes current research to Energy Minister, Claire Perry, during a visit to the Universdity of Edinburgh's School of Geosciences labs in November 2018. Photo: Callum Bennetts/Maverick Photo Agency|