Carbonated Fluid Flow through Ultramafic Rocks from Australia and New Zealand: Assessing fracture transmissivity and mineral changes via X-ray computed tomography imaging

This study investigates the impact of CO 2 injection on mineral transformations and fracture transmissivity within fractured ultramafic rocks, essential for evaluating in-situ carbon mineralization potential. Experiments were conducted using continuous injections of dry CO 2 and carbonated water under controlled temperature (25 °C to 55 °C) and pressure (2.07 MPa to 4.83 MPa) conditions in a high-pressure triaxial cell. Changes in mineral volume, fracture transmissivity, and surface morphology were quantitatively monitored using X-ray micro-computed tomography ( μ CT) and interferometry. Results indicated significant volume alterations of serpentine and olivine, driven primarily by hydration and serpentinization reactions. In contrast, dry CO 2 injections showed negligible influence on transmissivity. Carbonated water injections initially decreased transmissivity, which stabilized over time, highlighting the complex interplay between fluid chemistry, mineralogical evolution, and fracture dynamics. These findings provide critical insights for upscaling CO 2 mineralization strategies in fractured ultramafic reservoirs and emphasize the need for future studies over broader ranges of temperature, pressure, and reaction duration. • The study investigates the relationship between CO 2 injection and mineralogical transformations in fractured ultramafic rocks, using continuous injection experiments, X-ray micro-computed tomography, and interferometry. • Results indicate significant changes in fracture transmissivity and surface morphology, with notable shifts in mineral volumes, especially serpentine and olivine, highlighting the dynamics of hydration and serpentinization. • Carbonated water injections initially reduce fracture transmissivity, which stabilizes over time, while dry CO 2 injections show minimal impact, illustrating the complex connection between mineralogy and physical chemistry in CO 2 mineralization within fractured geological reservoirs.