Institute of GeoEnergy Engineering, Heriot-Watt University, Edinburgh, UK.
Department of Geoscience and Engineering, Delft University of Technology, Delft, The Netherlands.
Sci Rep. 2023 Jul 13;13(1):11312. doi: 10.1038/s41598-023-37725-6.
The traditional model of solid dissolution in porous media consists of three dissolution regimes (uniform, compact, wormhole)-or patterns-that are established depending on the relative dominance of reaction rate, flow, and diffusion. In this work, we investigate the evolution of pore structure using numerical simulations during acid injection on two models of increasing complexity. We investigate the boundaries between dissolution regimes and characterize the existence of a fourth dissolution regime called channeling, where initially fast flow pathways are preferentially widened by dissolution. Channeling occurs in cases where the distribution in pore throat size results in orders of magnitude differences in flow rate for different flow pathways. This focusing of dissolution along only dominant flow paths induces an immediate, large change in permeability with a comparatively small change in porosity, resulting in a porosity-permeability relationship unlike any that has been previously seen. This work suggests that the traditional conceptual model of dissolution regimes must be updated to incorporate the channeling regime for reliable forecasting of dissolution in applications like geothermal energy production and geologic carbon storage.
多孔介质中固溶的传统模型由三种溶解状态（均匀、紧密、虫孔）或模式组成，这些状态的建立取决于反应速率、流动和扩散的相对主导地位。在这项工作中，我们使用数值模拟研究了在两种复杂度不断增加的模型上进行酸注入时孔隙结构的演变。我们研究了溶解状态之间的边界，并确定了第四种溶解状态的存在，称为通道化，其中初始快速流动途径优先通过溶解而扩大。在孔喉大小分布导致不同流动途径的流速存在数量级差异的情况下，会发生通道化。这种仅沿着主要流动路径的溶解聚焦会导致渗透率立即发生较大变化，而孔隙度的变化相对较小，从而导致渗透率与孔隙度的关系与以前所见的任何关系都不同。这项工作表明，为了可靠地预测地热能源生产和地质碳储存等应用中的溶解，必须更新传统的溶解状态概念模型，以纳入通道化状态。
