One way to reduce greenhouse emissions while minimising disruption to high-carbon industries is to capture the emitted carbon dioxide before it enters the atmosphere, then store it deep underground at high pressure, inside porous rocks.
The successful storage of the carbon dioxide (CO2) depends on the interaction between existing salty groundwater and the injected CO2 inside the labyrinth of sub-millimeter gaps in the underground rocks.
The key questions are: does the CO2 form tiny bubbles in which it is trapped? How fast does it dissolve in the water? Does it eventually react with the rock to form a permanently stored solid? All this is complicated by the fact that CO2 is a supercritical fluid at subsurface temperatures and pressures.
The Department of Applied Mathematics, Research School of Physics and Engineering, at ANU is using its custom X-ray microtomographic facility, along with specially designed high pressure flow apparatus to directly visualise the CO2-water interaction inside rocks. This provides a unique tool that will provide a better understanding of what is happening when we try to sequester carbon dioxide deep underground.
In the next 50 years, the world's fuels must be decarbonised. Endex thermoreactive principles underpin new high efficiency systems for separating carbon from fuels and flue gases. In collaboration with Imperial College London, the University of Leeds, CanMet Energy, and an industry partner, researchers in this group are developing a suite of Endex carbon capture technologies.
Dr Rowena Ball is leading a major collaborative project with the Global CCS Institute that aims to design and build a universial toolkit for effectively comparing the efficiency and capture penalty of different carbon capture systems using exergy analysis. The CCS research group has received major infrastructure funding and made some important findings in work. For instance, in association with the Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC), the ANU was granted $5.1m in infrastructure funding from the Department of Education’s Education Investment Fund (EIF) that supports clean energy research infrastructure. This funding is being used to construct a lab that will provide imaging and core-flooding capabilities that are critical for determining the viability of carbon storage within aquifers at the CCS flagship sites.
In work supported by the Australian National Low Emissions Coal Research & Development (ANLEC R&D), researchers at the ANU x-ray CTLab successfully conducted core-flow studies of super-critical CO2 (scCO2) and brine at elevated pressure and temperature in an x-ray micro-CT instrument. These experiments provide direct 3D imaging of the distribution of scCO2 within the pores of rocks that come from a proposed carbon storage site in Queensland. Early results indicate that scCO2 is strongly non-wetting relative to brine and that high levels of capillary trapping of CO2 is possible at the trailing edge of a migrating CO2 plume.
In further work supported by the ANLEC R&D program, a comprehensive study was undertaken to determine suitable pore-scale modelling techniques for super-critical CO2: brine flow at proposed sequestration sites. The research explored major questions about the role of surface forces, buoyancy, viscosity, flow rate and pore structure. We concluded that the relatively lightweight method of quasi-static pore-network modelling is suitable for the proposed aquifers at all locations except near wellbore.