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Stress field orientation controls on fault leakage at a natural CO2 reservoir
Solid Earth ( IF 3.4 ) Pub Date : 2020-07-22 , DOI: 10.5194/se-11-1361-2020
Johannes M. Miocic , Gareth Johnson , Stuart M. V. Gilfillan

Travertine deposits present above the St. Johns Dome natural CO2 reservoir in Arizona, USA, document a long (>400 kyr) history of surface leakage of CO2 from a subsurface reservoir. These deposits are concentrated along surface traces of faults, implying that there has been a structural control on the migration pathway of CO2-rich fluids. Here, we combine slip tendency and fracture stability to analyse the geomechanical stability of the reservoir-bounding Coyote Wash Fault for three different stress fields and two interpreted fault rock types to predict areas with high leakage risks. We find that these areas coincide with the travertine deposits on the surface, indicating that high-permeability pathways as a result of critically stressed fracture networks exist in both a fault damage zone and around a fault tip. We conclude that these structural features control leakage. Importantly, we find that even without in situ stress field data, the known leakage points can be predicted using geomechanical analyses, despite the unconstrained tectonic setting. Whilst acquiring high-quality stress field data for secure subsurface CO2 or energy storage remains critical, we shown that a first-order assessment of leakage risks during site selection can be made with limited stress field knowledge.

中文翻译:

天然CO 2储层断层渗漏的应力场方向控制

存在 于美国亚利桑那州圣约翰斯穹顶天然CO 2储层上方的钙华沉积物,记录了从地下储层中CO 2地表泄漏的漫长历史(> 400 ?? kyr)。这些沉积物沿断层的表面痕迹集中,这意味着对CO 2的迁移路径已进行了结构控制。富含液体。在此,我们结合滑移趋势和裂缝稳定性,分析了在三个不同应力场和两种解释的断层岩石类型下,储层边界的土狼洗断层的地质力学稳定性,以预测具有高泄漏风险的区域。我们发现这些区域与表面的钙华沉积相吻合,这表明由于断层破坏区域和断层尖端附近都存在严重应力裂缝网络而导致的高渗透率途径。我们得出结论,这些结构特征可控制泄漏。重要的是,我们发现即使没有现场应力场数据,尽管构造环境不受限制,但仍可以使用地质力学分析来预测已知的泄漏点。在获取高质量应力场数据以确保地下CO 2安全的同时 或能量存储仍然至关重要,我们证明了在有限的应力场知识下可以对选址期间的泄漏风险进行一阶评估。
更新日期:2020-08-20
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