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.