Synergistic Effects of Weak Alkaline-Surfactant-Polymer and SiO2 Nanoparticles Flooding on Enhanced Heavy Oil Recovery

The alkaline-surfactant-polymer (ASP) enhanced oil recovery (EOR) is a promising tertiary oil recovery technique for maximizing oil production. However, strong alkaline (e.g., NaOH) or high concentration of an alkali may cause new problems, such as formation erosion, alkali deposition, and high production costs. In this study, a new EOR method was proposed by combining a traditional weak alkaline (Na2CO3) ASP flooding and nanotechnology. We investigated the synergistic effects of weak alkaline ASP chemicals and SiO2 nanoparticles on the EOR through comprehensive experiments. The efficacy of the mixtures was examined using a framework including interfacial tension and wettability characterizations, flow visualization experiments of emulsion, and oil recovery tests under reservoir temperature conditions. Moreover, the effects of weak alkaline ASP chemicals and SiO2 nanoparticles on interfacial properties and the EOR were carefully investigated by a comprehensive analysis. The experimental results show that the ASP + SiO2 nanoparticles mixture has a greater ability to reduce the interfacial tension (IFT) between oil and water as well as their contact angle, compared with a hydrolyzed polyacrylamide (HPAM)/ASP-only solution. The ASP + SiO2 nanoparticles mixture is better than the HPAM/ASP-only solution in profile control and displacement efficiency after water flooding. The SiO2 NPs/ASP mixture increases the oil recovery by 6.67% of original oil in place (OOIP), compared to the ASP-only solution. In visualization flooding experiments, the ASP + SiO2 nanoparticles mixture forms strong viscoelastic, thermodynamic, and kinetic stability of the droplets, thereby resulting in a larger sweep efficiency and better displacement efficiency by the stable blocking effects and strong scratch effect. It indicates that this new method can enhance oil recovery, have potential to reduce chemical agent cost, and avoid probable formation erosion and alkali deposition.