We present constant-flow experiments of high-pressure CO₂-saturated fluid through fracture channels in Portland cement with three different fracture geometries and with three different flow rates. The experiments were conducted in etched cement wafers within a microfluidics device. The evolution of pH was observed optically using phenolphthalein dye and changes in channel volume due to dissolution and/or precipitation were characterized with profilometry and scanning electron microscopy. Abundant precipitation for all three geometries was observed in the low flow-rate experiments, while only dissolution was observed in the high-flow rate experiments. The results bracket self-sealing versus self-opening behavior. The observed functional relationship among flow rate, fracture geometry and aperture in relation to self-sealing is consistent with a diverse set of experiments in the literature conducted under widely varying conditions and with behavior predicted in recent numerical models (Brunet et al., 2016; Cao et al., 2015; Guthrie et al., 2018; Iyer et al., 2017). The results confirm that self-sealing is a quantifiable behavior in ordinary Portland cement systems that is favored at low flow rates and in small-aperture or small hydraulic diameter fracture systems with clear limits imposed by dissolution-dominated conditions of high flow rates.

我们提出高压CO _2的恒流实验三种不同裂缝几何形状和三种不同流速的硅酸盐水泥裂缝通道中的饱和流体。实验是在微流体装置内的蚀刻水泥晶片上进行的。用酚酞染料光学观察pH的变化，并用轮廓光度法和扫描电子显微镜表征由于溶解和/或沉淀引起的通道体积的变化。在低流速实验中观察到所有三个几何形状的大量沉淀，而在高流速实验中仅观察到溶解。结果表明自密封性能与自打开性能之间的关系。观察到的流量之间的函数关系，与自密封有关的裂缝几何形状和孔径与文献中在广泛变化的条件下进行的一系列实验以及最近的数值模型中预测的行为相一致（Brunet等人，2016; Cao等人，2015; Guthrie等人，2018； Iyer等人，2017）。结果证实，自密封在普通波特兰水泥系统中是一种可量化的行为，在低流量和小孔径或小水力直径裂缝系统中均受优先考虑，而高溶出度主导的溶出条件对自密封具有明显的限制。