Creep of CarbFix basalt: influence of rock–fluid interaction

• Published in: Solid Earth
• Main Authors: Xing, Tiange, Ghaffari, Hamed O., Mok, Ulrich, Pec, Matej
• Format: Text
• Language: English
• Published: 2022
• Subjects: Iceland
• Online Access: https://doi.org/10.5194/se-13-137-2022; https://se.copernicus.org/articles/13/137/2022/

Geological carbon sequestration provides permanent CO 2 storage to mitigate the current high concentration of CO 2 in the atmosphere. CO 2 mineralization in basalts has been proven to be one of the most secure storage options. For successful implementation and future improvements of this technology, the time-dependent deformation behavior of reservoir rocks in the presence of reactive fluids needs to be studied in detail. We conducted load-stepping creep experiments on basalts from the CarbFix site (Iceland) under several pore fluid conditions (dry, H 2 O saturated and H 2 O + CO 2 saturated) at temperature, T ≈80 ∘ C and effective pressure, P eff =50 MPa, during which we collected mechanical, acoustic and pore fluid chemistry data. We observed transient creep at stresses as low as 11 % of the failure strength. Acoustic emissions (AEs) correlated strongly with strain accumulation, indicating that the creep deformation was a brittle process in agreement with microstructural observations. The rate and magnitude of AEs were higher in fluid-saturated experiments than in dry conditions. We infer that the predominant mechanism governing creep deformation is time- and stress-dependent subcritical dilatant cracking. Our results suggest that the presence of aqueous fluids exerts first-order control on creep deformation of basaltic rocks, while the composition of the fluids plays only a secondary role under the studied conditions.