Study on the mechanical mechanism of dynamic wetting of sodium dodecyl sulfonate solutions containing inorganic salt additives

Wettability is an important factor that influences surfactant oil displacement efficiency, where surfactant solutions wet rock surfaces better and have lower interfacial tensions with crude oil, thus enhancing the oil recovery rate. Therefore, understanding the wetting of rock surfaces and selecting suitable surfactant solutions are essential for enhanced oil recovery. In this paper, a self-built system to measure the lateral friction at solid and liquid interfaces was established, and the effects of different types and concentrations of inorganic salt additives on the dynamic wettability of the surfactant solution on the solid surface were studied. A rough silica surface was used to simulate the reservoir environment, and methylene chloride was used as the simulation oil. The experimental results show that when the concentration of sodium dodecyl sulfonate is lower than the critical micelle concentration, the inorganic salt additives (NaCl, Na2SO4, and KCl) affect the surface tension, contact angle, and lateral friction of the solution. As the concentration of the inorganic salt additives increased, the surface tension and contact angle of the solution continuously decreased, the lateral friction of the solution on the simulated silica surface increased, and the wettability of the surfactant solution on the solid surface improved.