Abstract. Geological carbon sequestration provides permanent CO₂ storage to mitigate the current high concentration of CO₂ in the atmosphere. CO₂ 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 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, H₂O-saturated and H₂O+CO₂-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 ultimate failure strength, well below the stress level at the onset of bulk dilatancy. 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 sub-critical 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.

中文翻译：

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CarbFix 玄武岩蠕变：岩液相互作用的影响

摘要。地质碳封存提供永久的 CO ₂储存，以减轻目前大气中 CO _{2 的}高浓度。玄武岩中的CO ₂矿化已被证明是最安全的存储选择之一。为了该技术的成功实施和未来改进，需要详细研究存在反应流体时储层岩石随时间变化的变形行为。我们在几种孔隙流体条件（干燥、H ₂ O 饱和和 H ₂ O+CO ₂饱和）、温度、T≈80 °C 和有效压力下，对来自 CarbFix 站点（冰岛）的玄武岩进行了载荷步进蠕变实验， P _EFF = 50 MPa，在此期间我们收集了机械、声学和孔隙流体化学数据。我们观察到应力低至最终破坏强度的 11% 时的瞬态蠕变，远低于体积膨胀开始时的应力水平。声发射 (AE) 与应变积累密切相关，表明蠕变变形是一个与微观结构观察一致的脆性过程。流体饱和实验中 AE 的速率和幅度高于干燥条件。我们推断控制蠕变变形的主要机制是与时间和应力相关的亚临界膨胀开裂。我们的结果表明，含水流体的存在对玄武岩的蠕变变形产生一级控制，而流体的成分在研究条件下仅起次要作用。