Synthesis and Mechanistic Investigation of an Amphiphilic Polymer in Enhancing Extra-Heavy Oil Recovery via Viscosity Reduction

When applied to extra-heavy oil, conventional polymer surfactants exhibit poor efficacy in reducing viscosity and have limited adaptability. In this work, a novel amphiphilic polymer named PAADB was prepared by incorporating 2-acryloylamino-2-methyl-1-propanesulfonic acid (AMPS), benzyldimethyl [2-[(1-oxoallyl) zoxy] propyl] ammonium chloride (DML), and poly(ethylene glycol) methyl ether acrylate (BEM) into the main chain of acrylamide through free radical polymerization. PAADB exhibited outstanding interfacial activity, water-phase thickening ability, and emulsifying performance. The critical micelle concentration of PAADB was approximately 2500 mg/L, with a viscosity of 84.69 mPa·s at 50 °C. Additionally, interfacial tension experienced a notable decrease from 46.53 to 14.56 mN/m. At an optimal concentration of 4000 mg/L, PAADB reduced the viscosity of extra-heavy oil by over 92% across various temperatures and by more than 93% for different types of extra-heavy oil. PAADB demonstrated excellent emulsification ability and emulsion stability, effectively dispersing crude oil to create water-in-oil droplets measuring 35.33 μm in size. Meanwhile, molecular dynamics simulations further unveiled the viscosity reduction mechanism of PAADB. The hydrophilic groups within PAADB molecules are regularly distributed on the water interface, while the hydrophobic groups infiltrate the oil molecules to form a stable interfacial film. PAADB and asphaltene spontaneously form a sandwich structure, reducing intermolecular forces and disrupting the interlayer structure of asphaltene molecules. In general, this novel amphiphilic polymer demonstrates broad applicability and potential in extra-heavy oil recovery, providing valuable insights for the development of new heavy oil viscosity reducers (HOVRs).