Study of surfactant-polymer system containing a novel ternary sulfonated polyacrylamide on the oil-water interface properties

Role of the Polymer in the Emulsion Stability of an Amphoteric Polyacrylamide in Different Flooding Systems

Polymers with high viscosity and good viscosity-temperature property have attracted attention as chemical agents for enhanced oil recovery. The role of polymers in the emulsifying stability of an amphoteric polyacrylamide (TSPAM) with good viscosity-temperature property in different flooding systems was investigated by means of a new emulsion stability model and molecular simulations. The results indicated that TSPAM exhibited superior emulsion stability compared to hydrolyzed polyacrylamide (HPAM). The half-life of emulsions containing TSPAM was 1-7 min longer than that of emulsions containing HPAM. The results of molecular simulation revealed that the HPAM molecules adsorbed at the oil-water interface in a "point adsorption" mode, whereas the TSPAM molecules adsorbed in a "surface adsorption" mode, resulting in higher interfacial adsorption efficiency and more stable interfacial film. The polymer flooding systems containing TSPAM showed a larger interfacial thickness of 1.029 nm and higher emulsification efficiency compared to the polymer flooding systems containing HPAM. The addition of Na2CO3 or surfactants further improved the stability of emulsions in the binary systems containing TSPAM. The stability of emulsions containing all three oil displacement agents was the strongest, with the half-life extended by 3.8-13.6 min. Amphoteric polyacrylamide significantly enhanced the stability of the emulsions. Through the integration of experimental and molecular simulation techniques, the molecular structure of polyacrylamide can be optimized, facilitating the development of more efficient oil recovery formulations for enhanced oil recovery applications.

Demulsification of oily wastewater using a nano carbon black modified with polyethyleneimine

In this work, nano carbon black was modified with polyethyleneimine (CB-PEI) under an ultrasonic field. The obtained product was used as a demulsifier to break oily wastewater. Morphology, structure, and chemical composition of CB-PEI were systematically analyzed. Bottle test was carried out to evaluate the influence of dosage, pH value and salinity on the demulsification efficiency of the emulsion. The results showed that the light transmittance of water phase (TSW) after the demulsification was 79.1% and corresponding oil removal rate (ORR) could reach up to 99.4% with 60 mg/L of CB-PEI at ambient temperature for 30 min. In addition, the possible demulsification mechanism was explored by dynamic interface tension (IFT), elasticity modulus, wettability, self-assemble of interfacial membrane, zeta potential and micrograph analysis. It indicated that CB-PEI had an appropriate amphiphilicity and good interfacial activity, which could improve it quickly transfer to the oil-water interface and result in the oil-water separation. The current work provides a simple method to prepare a demulsifier with excellent performance, so it has a good application prospect for the treatment of oil-water emulsions.

Effect of Oil-Displacing Agent Composition on Oil/Water Interface Stability of the Asphaltene-Rich ASP Flooding-Produced Water

In this work, the effect of oil-displacing agent composition on oil/water interface stability of the asphaltene-rich alkali-surfactant-polymer (ASP) flooding-produced water was systematically investigated, especially from the perspective of the interaction between oil displacement agents and asphaltene at the oil/water interface. Primarily, adsorption behavior of the artificial and natural interfacial substances (oil displacement surfactant and asphaltenes) on the oil/water interface was investigated by molecular dynamics simulation. The oil displacement surfactant and asphaltenes formed a cross-linked and compact interfacial film structure, which significantly enhanced the interface stability; the more the oil displacement surfactants adsorbed on the interface, the more stable is the cross-linked structure formed between them and asphaltenes. Then, the interfacial property variations that are originating from the interactions differences between oil displacement agents and asphaltenes were monitored via interfacial tension, zeta potential, and interfacial film rheology tests. Moreover, the effect of oil displacement agent concentrations on the interfacial film thinning and rupture kinetic behavior was further investigated. Finally, cream experiments were conducted to verify the effect of oil displacement agent composition on the oil/water separation efficiencies of asphaltene-rich ASP flooding-produced water. When 5% asphaltenes was added, the creaming oil removal rate reduced from 90.0 to 85.3% at 19 h. The interactions between asphaltenes and oil displacement agents immensely enhance the oil/water interfacial film strength and impede the oil/water separation process.