Department of Chemical Engineering, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
Institute of Applied Mechanics (MIB), Pfaffenwaldring 7, Stuttgart 70569, Germany.
Environ Sci Technol. 2024 Feb 13;58(6):2728-2738. doi: 10.1021/acs.est.3c06758. Epub 2024 Jan 17.
Understanding geochemical dissolution in porous materials is crucial, especially in applications such as geological CO storage. Accurate estimation of reaction rates enhances predictive modeling in geochemical-flow simulations. Fractured porous media, with distinct transport time scales in fractures and the matrix, raise questions about fracture-matrix interface dissolution rates compared to bulk dissolution rate and the scale-dependency of reaction rate averaging. Our investigation delves into these factors, studying the impact of flow rate and mineralogy on interface dissolution patterns. By injecting carbonated water into carbonate rock samples containing a central channel (mimicking fracture hydrodynamics), our study utilized μCT X-ray imaging at 3.3 μm spatial resolution to estimate the reaction rate and capture the change in pore morphology. Results revealed dissolution rates significantly lower (up to 4 orders of magnitude) than batch experiments. Flow rate notably influenced fracture profiles, causing uneven enlargement at low rates and uniform widening at higher ones. Ankerite presence led to a dissolution-altered layer on the fracture surface, showing high permeability and porosity without greatly affecting the dissolution rate, unlike clay-rich carbonates. This research sheds light on controlling factors influencing dissolution in subsurface environments, critical for accurate modeling in diverse applications.
理解多孔介质中的地球化学反应溶解过程至关重要，特别是在地质 CO2 储存等应用中。准确估计反应速率可以增强地球化学流动模拟中的预测模型。具有明显裂缝和基质传输时间尺度的裂缝多孔介质，引发了关于裂缝-基质界面溶解速率与整体溶解速率以及反应速率平均的尺度依赖性的问题。我们的研究深入探讨了这些因素，研究了流速和矿物学对界面溶解模式的影响。通过将碳酸水注入含有中央通道的碳酸盐岩样品中（模拟裂缝水动力），我们的研究利用 3.3μm 空间分辨率的 μCT X 射线成像来估计反应速率并捕捉孔隙形态的变化。结果表明，溶解速率明显低于（高达 4 个数量级）批实验。流速显著影响裂缝形态，在低流速下导致不均匀扩大，而在高流速下则导致均匀扩大。铁白云石的存在导致裂缝表面形成溶解改变层，表现出高渗透性和孔隙度，而不会像富含粘土的碳酸盐岩那样大大影响溶解速率。这项研究揭示了影响地下环境中溶解过程的控制因素，对于各种应用中的准确建模至关重要。
