Injection of low-salinity or smart water into the reservoir is one of the most common EOR techniques. This technique leads to more oil recovery in comparison to reservoir water and seawater injection. Several mechanisms explain the reasons for this increased recovery level, the most important of which is the wettability alteration towards water-wet conditions. However, in recent years, further mechanisms have been added to the previous ones as the main or complementary mechanism. One of these newly added mechanisms is the performance of oil as a semi-permeable membrane between connate and low-salinity waters. According to this mechanism, water molecules move from low-salinity water through oil to connate water due to the difference in their osmotic pressure (difference in chemical potential), which works as the driving force, until the system moves toward equilibrium in concentration. Introducing water molecules into connate water causes the swelling of connate water, and eventually moves the oil towards the pore throats. In this study, experiments have been performed on capillary tubes, while ignoring the effect of fluid-rock interactions to investigate the proposed theory. Experimental results confirmed the role of osmotic theory. Furthermore, a decrease in the salinity of the low-salinity water causes the oil-droplets' displacement to increase, whereas further reductions in the salinity of the injected water cause lower displacements. Therefore, there is an optimum value of low-salinity water concentration to obtain the highest possible oil drop displacement. The optimum values for the tested samples in this study were about 5000–10000 ppm. Additionally, it was found that among all of the essential seawater salts, potassium chloride leads to the highest oil drop displacement; and among oil samples, heptane showed better membrane-like performance in comparison to toluene and crude oil.

将低盐度或智能水注入储层是最常用的EOR技术之一。与油藏注水和注入海水相比，该技术可提高采收率。有几种机理解释了提高回收率的原因，其中最重要的是对水湿条件的可湿性改变。然而，近年来，在先前的机制中已经添加了其他机制作为主要机制或补充机制。这些新添加的机制之一是油在原生水和低盐度水之间作为半透膜的性能。根据这种机制，由于水分子的渗透压差（化学势差）（作为驱动力），水分子从低盐度水通过油流向原生水，直到系统达到浓度平衡。将水分子引入原生水中会导致原生水膨胀，并最终使油流向孔喉。在这项研究中，已经在毛细管上进行了实验，而忽略了流体-岩石相互作用的影响来研究所提出的理论。实验结果证实了渗透理论的作用。此外，低盐度水的盐度降低导致油滴的排量增加，而注入水的盐度的进一步降低导致较低的排量。因此，存在一个低盐度水浓度的最佳值以获得最大的油滴位移。在这项研究中，测试样品的最佳值约为5000-10000 ppm。另外，发现在所有必需的海水盐中，氯化钾导致最高的油滴置换量；在石油样品中，庚烷比甲苯和原油具有更好的膜状性能。