Faults in CO2 storage: Anisotropy in flow and irregular displacement gradients informing reactivation

Current understanding of extensional faults, which are essential for subsurface CO2 storage, reveals that fault risk assessment and modeling are significantly hindered by uncertainty. This underscores the need for insights into the datasets and methodologies used for evaluating fault sealing and reactivation. Data on fault architecture from outcrops, combined with mechanical insights, indicate the presence of hydraulic anisotropy and varying strength relationships within faults that influence their potential for reactivation. We propose that large portions of faults may yield through minor slip events or creep, while sticky spots are responsible for larger fault slip events. Enhancing our detection and understanding of these sticky spots – primarily characterized by abrupt displacement gradients that require further investigation - could improve risk assessment, monitoring, and mitigation strategies related to fault reactivation and inform seismic activity in CO2 storage initiatives.