Wettability alteration of quartz surface in the presence of low salinity water and low salinity surfactant solution

Wettability is a key parameter that controls the mobility of residual oil in a depleted oil reservoir. Recently, low salinity water (LSW) and low salinity surfactant (LSS) solutions have been used to enhance oil recovery (EOR) by altering the wettability of the reservoir rock toward a water-wet environment. The main aim of this study was to systematically investigate the effect of the salt, oil, surfactant type, temperature, and pressure on the wettability of an oil-water-rock system. The behavior of oil samples (crude oil, dodecane, and decane) was measured on a quartz surface in the presence of LSW and LSS solutions using the different structures of surfactants. Two distinct LSWs were prepared: one containing monovalent salt (NaCl) and another divalent salt (CaCl₂) at a fixed concentration. Furthermore, four varieties of LSS were prepared by adding single-tailed (SDS-sodium dodecyl sulfate) and double-tailed (AOT-dioctyl sodium sulfosuccinate) surfactants into LSW at a fixed concentration. The results show that with an increase in pressure from 0.1 MPa to 5 MPa, two distinct trends in the contact angle of oil on the quartz surface in the presence of LSW and LSS. While, raising temperature from 25 to 50 °C, the contact angle of oil shifts toward oil-wet for both cases. In addition, thermogravimetric analysis (TGA) and zeta potential of oil-aged quartz powder in the LSW and LSS provided further insight into the wettability alteration of the quartz surface. This study offers key insights into quartz surface wettability alteration using LSW and LSS systems for EOR.