Pores connected to fractures provide an increased surface area for fluid-rock interactions when reactive fluids, such as CO₂-saturated water, flow within fractures. Diffusion-controlled transport of ions including dissolved CO₂, Ca²⁺, Mg²⁺, Fe²⁺, and Si within the connected pore network can lead to local mineral undersaturation or supersaturation and respective local dissolution or precipitation of secondary minerals. In this study, a diffusion-controlled experiment was conducted on a fractured basalt under subsurface conditions (60°C and 80 bars) to investigate the changes in the pore volume, the connectivity within the pore network, the pore and throat size distribution and to quantify the volume of dissolved and precipitated mineral phases. CO₂-saturated water with a supply of ions from the dissolution of basalt powder was reacted with an artificially fractured basalt sample over 12 weeks. The net pore volume of the sample decreased by 158 mm³, equivalent to 7.7% of the initial pore volume (2,041 mm³). The number of pores decreased considerably (15%) while the decline in the number of throats was small (4%) suggesting precipitation primarily occurred in pores. The number of isolated pores declined, which is attributed to mineral dissolution leading to greater connectivity within the pore network. Overall, the results provide insights into the early phase of reactive fluid flow in fractured basalt eventually leading to self-sealing of fractures and the adjacent pore network.

中文翻译：

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裂缝附近玄武岩孔隙网络中孔隙几何形状和连通性的变化响应 CO2 饱和流体

当活性流体（例如 CO ₂饱和水）在裂缝内流动时，与裂缝相连的孔隙为流体-岩石相互作用提供了增加的表面积。离子的扩散控制传输，包括溶解的 CO ₂、Ca ²⁺、Mg ²⁺、Fe ²⁺, 和连接的孔隙网络内的 Si 会导致局部矿物欠饱和或过饱和以及相应的次生矿物局部溶解或沉淀。在这项研究中，在地下条件（60°C 和 80 巴）下对裂隙玄武岩进行了扩散控制实验，以研究孔隙体积的变化、孔隙网络内的连通性、孔隙和喉道尺寸分布以及量化溶解和沉淀的矿物相的体积。含有来自玄武岩粉末溶解的离子的CO ₂饱和水与人工破碎的玄武岩样品反应超过 12 周。样品的净孔体积减少了 158 mm ³，相当于初始孔体积（2,041 mm ³）。孔隙数量显着减少（15%），而喉道数量减少很小（4%），表明沉淀主要发生在孔隙中。孤立孔隙的数量减少，这归因于矿物溶解导致孔隙网络内更大的连通性。总体而言，这些结果提供了对断裂玄武岩中反应性流体流动的早期阶段的见解，最终导致裂缝和相邻孔隙网络的自封闭。