Abstract Large volumes of water containing friction-reducing additives are injected into target rock formations during hydraulic fracturing in shale gas production. The interactions between the fracking fluids and the reservoir rocks may increase the flowback and produced (FP) salinity, rendering the fluid ineffective for reuse and recycling. To explore the function of polyacrylamide (PAM; a widely applied friction-reducing additive) on the evolution of FP water salinity, three fluid-rock interaction experiments were conducted under relevant temperature conditions. Sr concentrations and 87Sr/86Sr were measured to identify mineral exchanges. Results showed that the dominant geochemical reactions were pyrite oxidation, carbonate, and silicate mineral dissolution, and halite dissolution; the hydrolysis of polyacrylamide facilitated mineral dissolution. Another one-tenth of carbonate was mobilized and the total oxidized pyrite mass was nearly 30 times greater on the function of PAM. These findings imply that the development of brine-tolerant polyacrylamide is necessary to effectively reuse and recycle FP water. This is beneficial for the environment as this minimizes the dependency on freshwater supplies. This study provides new information on the interactions between the fracturing fluid and the reservoir rocks and further elucidates the influence of polyacrylamide on wastewater salinity.

中文翻译：

---

聚丙烯酰胺在页岩气废水生产中提高矿化度的作用

摘要 页岩气生产中的水力压裂过程中，大量含有减摩添加剂的水被注入目标岩层。压裂液和储层岩石之间的相互作用可能会增加返排和产出 (FP) 盐度，使流体无法再利用和回收利用。为了探索聚丙烯酰胺（PAM；一种广泛应用的减摩添加剂）对 FP 水盐度演变的作用，在相关温度条件下进行了三个流体-岩石相互作用实验。测量 Sr 浓度和 87Sr/86Sr 以确定矿物交换。结果表明，主要的地球化学反应为黄铁矿氧化、碳酸盐和硅酸盐矿物溶解、岩盐溶解；聚丙烯酰胺的水解促进了矿物溶解。在 PAM 的作用下，另外十分之一的碳酸盐被动员起来，氧化黄铁矿的总质量增加了近 30 倍。这些发现意味着开发耐盐水聚丙烯酰胺对于有效地再利用和回收 FP 水是必要的。这对环境有益，因为这最大限度地减少了对淡水供应的依赖。这项研究提供了压裂液与储层岩石之间相互作用的新信息，并进一步阐明了聚丙烯酰胺对废水盐度的影响。这些发现意味着开发耐盐水聚丙烯酰胺对于有效地再利用和回收 FP 水是必要的。这对环境有益，因为这最大限度地减少了对淡水供应的依赖。这项研究提供了压裂液与储层岩石之间相互作用的新信息，并进一步阐明了聚丙烯酰胺对废水盐度的影响。这些发现意味着开发耐盐水聚丙烯酰胺对于有效地再利用和回收 FP 水是必要的。这对环境有益，因为这最大限度地减少了对淡水供应的依赖。这项研究提供了压裂液与储层岩石之间相互作用的新信息，并进一步阐明了聚丙烯酰胺对废水盐度的影响。