Adding polymers to the injection water in water-flooding oil recovery increases the viscosity and thereby enhances recovery factor. However, the beneficial effects are often counteracted by adsorption of polymer to the ambient mineral surface. In here, we used Quartz Crystal Microbalance with Dissipation (QCM-D) measurements to study the adsorption of the frequently used hydrolyzed polyacrylamide (HPAM), a weak polyelectrolyte, to silica and alumina model surfaces representing sandstone reservoirs. At pH 6 and 8 and concentrations from 1 mM to 100 mM of NaCl and CaCl₂, we find that negatively charged HPAM molecules generally adsorb more strongly to positively charged alumina surfaces. For silica surfaces, the presence of Ca²⁺ ions, which form strong complexes with the carboxyl groups on the polymer, as evidenced by titration measurements, strongly enhances HPAM adsorption. This effect is attributed to the formation of Ca²⁺-mediated ion bridges with the substrate. Kinetic measurements suggest a two-step adsorption process consisting of a primary polymer adsorption onto the surface followed – in most cases – by a slower secondary process, which involves rearrangements of previously adsorbed polymer molecules, including polymer-on-polymer adsorption.

在注水采油中将聚合物添加到注入水中可增加粘度，从而提高采收率。然而，有益效果通常通过聚合物吸附到周围矿物表面上而抵消。在这里，我们使用带耗散的石英晶体微天平（QCM-D）测量来研究常用的水解聚丙烯酰胺（HPAM）（一种弱聚电解质）对代表砂岩储层的二氧化硅和氧化铝模型表面的吸附。在pH为6和8且NaCl和CaCl ₂为1 mM至100 mM的浓度下，我们发现带负电的HPAM分子通常更强地吸附到带正电的氧化铝表面。对于二氧化硅表面，Ca ²⁺的存在滴定法测量表明，与聚合物上的羧基形成强配合物的离子可大大增强HPAM的吸附能力。该作用归因于与底物形成Ca ²⁺介导的离子桥。动力学测量结果表明，吸附过程分为两步，即一次聚合物在表面上的吸附，然后（大多数情况下）一个较慢的二次过程，该过程涉及先前吸附的聚合物分子的重排，包括聚合物对聚合物的吸附。