Defects along wellbore interfaces constitute potential pathways for CO₂ to leak from geological storage systems. In previous experimental work, we demonstrated that CO₂-induced reaction over length-scales of several meters can lead to self-sealing of such defects. In the present work, we develop a reactive transport model that, on the one hand, enables μm-mm scale exploration of reactions along debonding defects and, on the other hand, allows simulation of the large, 6 m-long samples used in our experiments. At these lengths, we find that interplay between flow velocity and reaction rate strongly affects opening/sealing of interfacial defects, and depth of chemical alteration. Carbonate precipitation in initially open defects decreases flow rate, leading to a transition from advection-dominated to diffusion-dominated reactive transport, with acidic conditions becoming progressively more confined upstream. We investigate how reaction kinetics, portlandite content, and the nature of the carbonate products impact the extent of cement alteration and permeability reduction. Notably, we observe that nonuniformity of the initial defect geometry has a profound effect on the self-sealing behavior and permeability evolution as observed on the meter scale. We infer that future wellbore models need to consider the effects of such aperture variations to obtain reliable upscaling relations.

中文翻译：

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沿脱胶井筒套管-水泥界面的富含CO _2的水流的米级反应输运模型

沿井眼界面的缺陷构成了CO ₂从地质存储系统泄漏的潜在途径。在先前的实验工作中，我们证明了CO ₂在几米的长度尺度上引起的反应可导致此类缺陷的自密封。在当前的工作中，我们开发了一种反应性传输模型，该模型一方面可以对沿着脱胶缺陷的反应进行微米级的探索，另一方面可以模拟用于我们的6m长的大型样品实验。在这些长度下，我们发现流速和反应速率之间的相互作用强烈影响界面缺陷的打开/密封以及化学变化的深度。最初开放的缺陷中的碳酸盐沉淀会降低流速，从而导致从对流为主向扩散为主的反应性迁移过渡，而酸性条件逐渐在上游受到限制。我们研究了反应动力学，波特兰含量，碳酸盐产品的性质会影响水泥改造和渗透率降低的程度。值得注意的是，我们观察到，初始缺陷几何形状的不均匀性对自密封性能和渗透性演变产生了深远的影响，如在仪表刻度上观察到的那样。我们推断，未来的井眼模型需要考虑这种孔径变化的影响，以获得可靠的放大比例关系。