Salinity effect on surfactant-assisted zinc oxide nanoparticles for enhanced oil recovery

Abstract

Several studies have focused on the advantages of applying nanotechnology to the enhanced oil recovery (EOR). This is because nanoparticles are unique due to their small size and large surface area. Metal oxide nanoparticles, including zinc oxide, have been proven to have favourable effects in EOR applications. However, the instability of nanoparticles is one of the most common issues. It has been established in the literature that using a surfactant with nanoparticles can stabilize the latter, lower the oil/water interfacial tension, and alter the wettability of reservoir rocks. It is also common knowledge that chemical EOR is affected by the salinity of formation water. Thus, the objectives of this study were to investigate the effects of salinity on zinc oxide nanoparticles with sodium dodecyl sulphate (SDS) over the interfacial tension and wettability, as well as to compare the recovery of oil by displacing sand packs with water, SDS, ZnO NPs with SDS, and the mixture of SDS, ZnO NPs, and NaCl. Particle size analysis (PSA) and zeta potential were determined to evaluate the size and stability of ZnO NPs before and after adding SDS. The surface tension for SDS was measured to identify the critical micellar concentration (CMC). The interfacial tension and contact angle were measured for different concentrations of nanofluid at ambient temperature and pressure. The concentration range for ZnO NPs was 0.02 to 0.1 wt%, while that for NaCl was 1000 to 30,000 ppm. The results showed that the size of the zinc oxide nanofluid decreased from 406.6 to 308.3 nm after adding SDS. The stability of ZnO nanofluid was confirmed to be improved after mixing with SDS through zeta potential readings of -11.1 mV to -53.3 mV. The CMC for SDS was recorded at 0.2 wt%. The optimum IFT value of 6.25 mN/m was obtained using a mixture of 0.2 wt% SDS, 0.06 wt% ZnO NPs, and 30,000 ppm NaCl. Meanwhile, the lowest contact angle of 45.6 º was achieved using a mixture of 0.2 wt% SDS, 0.06 wt% ZnO NPs, and 20,000 ppm NaCl. Oil recovery after water flooding was 36.1% of the original oil in place (OOIP), while the oil recovery after SDS flooding and SDS with zinc oxide NPs flooding recorded 52.3% and 58.3% OOIP, respectively. Ultimately, the mixture of SDS, zinc oxide NPs, and NaCl can recover up to 60.5% OOIP. The nanofluid mixture was found to be effective in EOR applications.