We develop a reactive transport model for dissolution of porous materials using a Continuous Time Random Walk (CTRW) formulation with first-order kinetics. Our model is validated with a dataset for a Ketton carbonate rock sample undergoing dissolution on injection of an acid, monitored using Nuclear Magnetic Resonance (NMR). The experimental data includes the 3D porosity distribution at the beginning and end of the experiment, 1D porosity profiles along the direction of flow during dissolution, as well as the molecular fluid displacement probability distributions (propagators). With the calibration of only a single parameter, we successfully predict the porosity changes and the propagators as a signature of flow heterogeneity evolution in the dissolution experiment.

We also demonstrate that heterogeneity in the flow field leads to an effective reaction rate, limited by transport of reactants, that is almost three orders of magnitude lower than measured under batch reaction conditions. The effective reaction rate predicted by the model is in good agreement with the experimentally measured rate. Furthermore, as dissolution proceeds, the formation of channels in the rock focused the flow in a few fast-flowing regions. The predicted dissolution patterns are similar to those observed experimentally. This study establishes a workflow to calibrate and validate the CTRW reactive transport model with NMR experiments.

我们使用具有一级动力学的连续时间随机游走（CTRW）公式，开发了用于多孔材料溶解的反应性运输模型。我们的模型已通过使用核磁共振（NMR）监测的酸注入后溶解的Ketton碳酸盐岩样品的数据集进行了验证。实验数据包括在实验开始和结束时的3D孔隙率分布，在溶解过程中沿流动方向的1D孔隙率分布以及分子流体位移概率分布（扩散剂）。通过仅校准一个参数，我们就可以成功地预测孔隙度的变化，并且将传播剂作为溶出度实验中流动非均质性演化的标志。

我们还证明，流场中的非均质性导致有效反应速率受到反应物传输的限制，这比分批反应条件下测得的效率低了近三个数量级。该模型预测的有效反应速率与实验测得的速率非常吻合。此外，随着溶解的进行，岩石中通道的形成将流动集中在几个快速流动的区域。预测的溶出度模式与实验观察到的相似。这项研究建立了通过NMR实验来校准和验证CTRW反应性传输模型的工作流程。