Integrating surfactant, alkali and nano-fluid flooding for enhanced oil recovery: A mechanistic experimental study of novel chemical combinations

In the present study, an extended series of interfacial tension (IFT) and contact angle experiments were performed to find the most promising alternative out of four conventional anionic surfactants, namely linear alkylbenzene sulfonic acid (LASA) and sodium dodecylbenzene sulfonate (SDBS) and amphoteric surfactants, i.e., cocamido propyl betaine (CAPB) and coconut di-ethanol amide (CDEA). All the studied surfactants could decrease the IFT and contact angle of the oil droplet on dolomite rock samples, with the IFT and contact angle reduced even further by introducing particular additives, namely alkali, nanoparticles, and salt. It has been experimentally found that mixtures of CAPB+Na₂CO₃ and CAPB+SiO₂ at their optimum concentrations are novel promising solutions for core flooding experiments at ambient conditions. The results of adsorption measurement tests revealed that the presence of sodium carbonate and silica nanoparticles could efficiently reduce the CAPB adsorption on the dolomite rock samples by 59.7% and 35.7%, respectively, as compared to the initial CAPB concentration. Moreover, the spontaneous imbibition results indicated that the CAPB+Na₂CO₃ and the CAPB+SiO₂ solutions yielded 18.2% and 14.7% higher oil recoveries from the dolomite rock samples, respectively, as compared to the synthetic formation water (SFW). Finally, the efficiency of the selected solutions for surfactant flooding was investigated by core flooding experiments on carbonate sister core samples, leading to 19.7% and 12.2% higher oil recoveries, as compared to SFW flooding, for the CAPB+Na₂CO₃ and the CAPB+SiO₂ solutions, respectively.