Creep of CarbFix Basalt: Influence of Rock-fluid Interaction
Creep of CarbFix Basalt: Influence of Rock-fluid Interaction
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DOI：
10.5194/se-2021-114
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发表时间：
2021-09
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影响因子：
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通讯作者：
Tiange Xing;H. Ghaffari;U. Mok;M. Peč
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文献类型：
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作者：
Tiange Xing;H. Ghaffari;U. Mok;M. Peč
抽象的。地质碳封存提供永久的二氧化碳储存，以缓解目前大气中高浓度的二氧化碳。玄武岩中的二氧化碳矿化已被证明是最安全的储存选择之一。为了成功实施和未来改进该技术，需要详细研究反应流体存在下储层岩石随时间变化的变形行为。我们对来自 CarbFix 站点（冰岛）的玄武岩在几种孔隙流体条件（干燥、H2O 饱和和 H2O+CO2 饱和）、温度 T≈80 °C 和有效压力 Peff = 50 MPa 下进行了载荷步进蠕变实验，在此期间我们收集了力学、声学和孔隙流体化学数据。我们观察到应力低至极限失效强度 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脆性过程，与微观结构观察结果一致。液体饱和实验中的 AE 发生率和程度均高于干燥条件下。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裂纹。我们的结果表明，含水流体的存在对玄武岩蠕变变形发挥一级控制作用，而流体的成分在研究条件下仅起次要作用。
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, Peff = 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.