摘要：Travertine deposits present above the St. Johns Dome natural CO2reservoir in Arizona, USA, document a long (>400 kyr) history ofsurface leakage of CO2 from a subsurface reservoir. These deposits areconcentrated along surface traces of faults, implying that there has been astructural control on the migration pathway of CO2-rich fluids. Here,we combine slip tendency and fracture stability to analyse the geomechanicalstability of the reservoir-bounding Coyote Wash Fault for three differentstress fields and two interpreted fault rock types to predict areas withhigh leakage risks. We find that these areas coincide with the travertinedeposits on the surface, indicating that high-permeability pathways as aresult of critically stressed fracture networks exist in both a fault damagezone and around a fault tip. We conclude that these structural featurescontrol leakage. Importantly, we find that even without in situ stress fielddata, the known leakage points can be predicted using geomechanicalanalyses, despite the unconstrained tectonic setting. Whilst acquiringhigh-quality stress field data for secure subsurface CO2 or energy storageremains critical, we shown that a first-order assessment of leakage risksduring site selection can be made with limited stress field knowledge.
