(509a) Reactive Transport Modeling of CO2 Mineralization in Fractured Basalt Formations

Fractured reservoirs are widespread in sedimentary basins globally, commonly found in sandstones, basalts, and carbonates. Among these, fractured basalt formations have emerged as a promising candidate for CO₂ storage due to the abundance of reactive silicate minerals, which can significantly accelerate the mineralization of injected CO₂. However, this ‘enhanced mineralization’ method is still at an early research stage, with considerable uncertainty regarding the achievable scale of CO₂ reduction. Central to this uncertainty are the existing knowledge gaps in the geochemical reaction kinetics governing mineral dissolution and precipitation under in-situ conditions, which is further complicated by the different silicate mineral groups and trace elements present in fractured basalt formations. Additionally, the longer timescales required for mineralization reactions pose limitations for experimental studies, highlighting the need for numerical simulation studies.

To address these knowledge gaps, this study utilizes a robust numerical simulation to investigate CO₂ mineralization in fractured basalts, with a focus on key silicate mineral groups, including olivine, pyroxene, plagioclase, glass, and alkali-feldspar. The study also examines the combined effects of the different mineral groups by varying mineral volume fractions to better understand the dissolution-precipitation kinetics on the petrophysical properties of the reservoir. Furthermore, the role of trace elements such as lead and chromium are examined to evaluate their combined influence on CO₂ mineralization efficiency in fractured basalt formations.

The results from the numerical simulations show that for all the mineral groups studied, mineralization of CO₂ was consistently higher in the fractured regions compared to the reservoir as a whole, primarily due to the increased surface area and enhanced flow of CO₂ within the fracture networks. Additionally, despite the similar chemical composition of the silicate mineral groups, the rates of mineralization observed in all mineral groups were distinct. The olivine group was particularly observed to have the highest reactivity amongst all the silicate mineral groups studied. In contrast, the presence of trace elements was found to reduce overall mineralization efficiency in the fractured basalt formations, likely due to their inhibitory effects on carbonate precipitation. These mineral reactions led to significant alterations in the petrophysical properties of the entire reservoir.

These findings provide valuable qualitative insights for evaluating and optimizing CO₂ storage sites based on mineralogical composition. By improving our understanding of how different silicate mineral groups and trace elements influence mineralization, this study contributes to closing key knowledge gaps and supports the advancement of the ‘enhanced mineralization’ method as a viable approach for CCS in fractured basalt formations.