UNDERSTANDING THE FATE OF INJECTED CARBON DIOXIDE IN BASALT RESERVOIRS

Addressing the escalating climate crisis demands urgent deployment of technologies capable of operating commercially to capture and store greenhouse gases, including carbon dioxide (CO₂). Geologic carbon mineralization is one such strategy that provides long-term storage security via the permanent storage of CO₂ as stable carbonates. The feasibility of this technology was highlighted by successful pilot demonstrations of carbon mineralization in basalt- one in Wallula, USA (led by PNNL) and another in Iceland (led by Carbfix hf.). To date, these remain to be the only field scale mineralization efforts undertaken worldwide, where in both cases rapid conversion of injected CO₂ to carbonates was found to have taken place. Using samples retrieved from the field demonstration, this work delineates the fate of CO₂ and identifies the source and fate of cations that play a key role in complex subsurface mineralization processes. Using x-ray fluorescence spectro-microscopy we highlight the unique zonation patterns within the formed carbonates and reveal the source and fate of Mn- a key, but generally overlooked, component during mineralization. Furthermore, we use atomic scale microscopy to identify exotic carbonate phases, not known to exist naturally or synthetically, that formed as part of the sequestration effort. Collectively, these results provide critical baseline data points for the parameterization and refinement of reactive transport models at the field scale required for the application of future Class VI permitting, and storage validation in reactive mafic reservoirs.