When carbon dioxide (CO2) comes in contact with mafic to ultramafic rocks (e.g. basalt, peridotite), mineral dissolution and precipitation reactions produce carbonate minerals . This process provides a pathway by which CO2 can be removed from the atmosphere and permanently stored in the geologic subsurface. Engineering this CO2 mineralization process has the potential to remove mega- to giga-tonnes of CO2 per year . To develop the full CO2 removal potential of these rocks, we must understand the fundamental processes of fluid flow and reactive transport of these fractured multi-scale rock systems, where permeability, porosity and reactive surface area are continually changing through time. The principal aim of this project is 1) to examine how geo-chemo-mechanical processes affect the overall CO2 mineralisation capacity of basalts and peridotites; and 2) to deliver physical and geochemical benchmark data for the development of a micro-scale mechanical model (pore scale) and an upscaled continuum model, the latter of which will be used to study and predict the chemo-hydraulic interactions between fractures and rock matrix during CO2 mineralisation.
Physical and geochemical properties of basalt and peridotite cores will be determined using a multitude of different techniques, including computer tomography (CT), scanning electron microscopy (SEM), porosimetry, x-ray fluorescence, as well as electrical and acoustic measurements. Subsequently, reactive transport experiments with CO2-saturated fluids on selected core samples using custom-made multi-fluid experimental rigs will be conducted at variable pressure and temperature conditions . Physical properties will be measured throughout the experiments to monitor changes induced by CO2 reactions. Outlet fluid samples will be collected for geochemical analyses. In addition, CT scans of experimental core samples will be performed post-experiment to document changes in physical properties. Subsamples of the cores will be subject to further analysis, including SEM-EDS. The data collected from these experiments will lead to the construction of micro-scale mechanical and continuum models.
The INSPIRE DTP programme provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at the National Oceanography Centre Southampton. Specific training will include:
· Training in state-of-the-art hydro-mechanical experiments using experimental rigs, including the analysis of permeability, ultrasonic P- & S-wave and electrical conductivity data.
· Training in computer tomography and SEM-EDS image analysis.
· Training in state-of-the art geochemical analysis (XRF, inductively coupled plasma optical emission spectroscopy).
· The student will be part of a world-class team of scientists of the U.S. Department of Energy funded ‘Center for Interacting Geo-processes in Mineral Carbon Storage’ based at the University of Minnesota (USA) with Georgia Institute of Technology (USA), Los Alamos National Laboratory (USA), Northwestern University (USA), and University of Southampton as partner organizations.
The student will benefit from a placement at the University of Minnesota or one of the project partner organizations to get further training in experimental hydromechanics or numerical modeling of reactive transport.