Rodríguez de Castro Antonio, Ben Abdelwahed Amine, Bertin Henri
I2M, Arts et Métiers Institute of Technology, CNRS, Esplanade des Arts et Métiers, 33405 Talence Cedex, France.
I2M, Arts et Métiers Institute of Technology, CNRS, Esplanade des Arts et Métiers, 33405 Talence Cedex, France.
J Contam Hydrol. 2023 Apr;255:104142. doi: 10.1016/j.jconhyd.2023.104142. Epub 2023 Feb 1.
This work presents a novel technique consisting in the use of yield stress fluids as blocking agents in porous media presenting pore-scale heterogeneities. The key feature of this method is that yield stress fluids only flow through the pores having a minimum size that depends on the applied pressure gradient. These fluids remain immobile in more and more pores as the pressure gradient is decreased. Therefore, the dimension of the pores which are invaded by the yield stress fluid can be controlled by adjusting the applied pressure gradient. Moreover, yield stress fluids are highly suitable blocking agents given the extremely high viscosity values that they exhibit in the pores. This allows for the diversion of the flow from greater to smaller pores during subsequent waterflooding stages, thus enhancing pollutant removal from the flow paths of small hydraulic conductance. A series of multiphase flow experiments were conducted in this study using well-characterized cores of artificial A10 sintered silicate. In these experiments, semidilute aqueous solutions of xanthan gum biopolymer were used as yield stress fluids to block the greatest pores. By doing so, considerably more pollutant was recovered by waterflooding. Furthermore, it was shown that an increase in polymer concentration does not always lead to a decrease in the size of the pores invaded by the blocking agent. Indeed, concentrated polymer solutions generate higher pressure gradients throughout the porous medium, which facilitates the invasion of small pores. Nevertheless, depending on the value of the yield stress-pressure gradient ratio, they may also develop extremely high viscosities that slow down their flow through such small pores. This work also presents a method to measure the volume of blocked pores using the results of tracer tests. The reported results suggest that using a polymer solution developing a yield stress as a selective blocking agent is a promising technique for soil remediation.
这项工作提出了一种新技术，该技术在于使用屈服应力流体作为具有孔隙尺度非均质性的多孔介质中的封堵剂。该方法的关键特性在于，屈服应力流体仅流经具有取决于所施加压力梯度的最小尺寸的孔隙。随着压力梯度降低，这些流体在越来越多的孔隙中保持不动。因此，通过调整所施加的压力梯度，可以控制被屈服应力流体侵入的孔隙尺寸。此外，鉴于屈服应力流体在孔隙中表现出的极高粘度值，它们是非常合适的封堵剂。这使得在后续注水阶段水流能够从小孔隙转向大孔隙，从而增强从小水力传导率流路中去除污染物的能力。在本研究中，使用特性良好的人工A10烧结硅酸盐岩心进行了一系列多相流实验。在这些实验中，使用黄原胶生物聚合物的半稀释水溶液作为屈服应力流体来封堵最大的孔隙。通过这样做，注水回收了更多的污染物。此外，研究表明聚合物浓度的增加并不总是导致封堵剂侵入的孔隙尺寸减小。实际上，浓聚合物溶液在整个多孔介质中产生更高的压力梯度，这有利于小孔隙的侵入。然而，根据屈服应力与压力梯度的比值，它们也可能产生极高的粘度，从而减缓其通过此类小孔隙的流动。这项工作还提出了一种利用示踪剂测试结果来测量被封堵孔隙体积的方法。报告的结果表明，使用产生屈服应力的聚合物溶液作为选择性封堵剂是一种很有前景的土壤修复技术。
