Design and synthesis of a new ionic liquid surfactant for petroleum industry

•A new IL surfactant is introduced for EOR purposes.•The proposed IL surfactant can tolerate harsh conditions of salinity.•50,000 ppm is an optimal salinity for the synthesized IL surfactant.•The oil–water IFT is reduced by 95.9% at CMC.•Both IFT reduction and wettability alteration occur upon addition of the surfactant. This study is intended to synthesize and assess a new pyridinium-based Ionic Liquid (IL) surfactant, 1-octadecyl-pyridinium bromide, in terms of crude oil–water Interfacial Tension (IFT) reduction and wettability alteration. The synthesized IL surfactant is firstly characterized through proton Nuclear Magnetic Resonance (1H NMR). Then, the pendant-drop and sessile drop techniques are employed to study crude oil–water IFT and the wettability of carbonate rocks. Based on the IFT results, the synthesized IL has a Critical Micelle Concentration (CMC) of 200 ppm, at which crude oil–water IFT reduces by 95.9 %, from an initial value of 23.7 mN/m to 0.97 mN/m. Increasing the salinity up to 100,000 ppm could not make the synthesized IL less effective than that of free from salinity, as the magnitude of IFT is obtained to be 0.938 mN/m at CMC. Based on the wettability investigation phase, the synthesized IL changes the wettability of carbonate slices from oil-wet to intermediate-wet (140.47°–90.97°). It is also observed that the synthesized IL can tolerate harsh salinity conditions as no appreciable change in the contact angle is noticed after increasing the salinity even up to 150,000 ppm (84.54° at CMC). It should be noted that an optimal salinity of 50,000 ppm is found based on the results of IFT and contact angle measurements. The introduced surfactant is expected to exhibit a significant positive impact on the oil recovery factor while implementing chemical flooding.