Petrophysical recipe for in-situ CO2 mineralization in basalt rocks

Abstract

In-situ carbon dioxide mineralization in basalt rocks has been identified as a scalable, fast, safe, permanent, and cost-effective method to offset the anthropogenic carbon dioxide emissions. In-situ carbon dioxide mineralization refers to underground carbon dioxide transformation to carbonate minerals in basalt reservoirs. Although current field applications achieved fast in-situ carbon dioxide mineralization, limited petrophysical criteria have been proposed to screen a potential site to implement in-situ carbon dioxide mineralization. To fill this knowledge gap, geochemical modellings were performed to find an optimal petrophysical recipe, including pressure, temperature, pH, and mineral composition, to conduct in-situ carbon dioxide mineralization. The geochemical modellings showed that increasing pressure was favourable to increase water uptake of carbon dioxide, host rock dissolution, and in-situ carbon dioxide mineralization. However, a higher temperature depressed the in-situ carbon dioxide mineralization. Furthermore, the in-situ carbon dioxide mineralization was unravelled to be heavily pH dependent. Most magnesite precipitated in pH range from 9 to 11. Moreover, the forsterite was identified as the major contributing minerals while anorthite, fayalite, and diopside played a minor role in the in-situ carbon dioxide mineralization. This investigation provided a general protocol to screen the optimal petrophysical conditions for in-situ carbon dioxide mineralization.