Carbon capture and storage (CCS) – the collection of carbon dioxide (CO2) from power stations and its injection underground – is an important technology to reduce CO2 emissions to the atmosphere and hence to mitigate climate change. The North Sea, with mature hydrocarbon fields and saline aquifers offers an attractive storage location for CO2 produced by the UK’s gas and coal-fired power plants. The principal concern with CCS is to ensure that the CO2 does not leak into the oceans or atmosphere over hundreds or thousands of years.
This project involves the design of a storage strategy where CO2 and brine are injected together followed by brine injection alone. This may render 80-90% of the CO2 immobile in pore-scale (10s m) droplets in the porous rock; over thousands to billions of years the CO2 may dissolve or precipitate as carbonate, but it will not migrate upwards and so is effectively sequestered. The CO2 is trapped during the decades-long lifetime of the injection phase, avoiding the need for extensive monitoring for centuries. The method does not rely on impermeable cap rock to contain the CO2; this is only a secondary containment for the small amount of remaining mobile gas. Furthermore, the reduced mobility ratio between injected and displaced fluids leads to a more uniform sweep of the aquifer leading a larger storage capacity than injecting CO2 alone.
The work involves a combination of one-dimensional analytical solutions to the non-linear transport equations coupled with pore and field-scale modelling of the pertinent physical processes.
Contact: Tara LaForce and Martin Blunt
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