Preparation and enhanced oil recovery mechanism of dual-shell amphiphobic fluorinated nano-polymer core–shell materials

Abstract This study developed dual-shell amphiphobic fluorinated polymer core–shell materials (AFPCSMs) for wettability alteration in tight oil reservoirs. The materials comprise silica nanoparticle cores (30 nm), γ-aminopropyltriethoxysilane methacrylic anhydride inner shells, and fluorinated polymer outer shells via 2,2,2-trifluoroethyl methacrylate dodecafluoroheptyl methacrylate copolymerization. Fourier transform infrared spectrometer, X-ray photoelectron spectroscopy, and thermogravimetric analyzer characterization confirmed successful dual-shell construction. AFPCSMs achieved superior amphiphobic properties with water contact angles of 145.3°, n -hexadecane contact angles of 132.6°, and surface free energy reduction to 1.44 mN/m (95.7% decrease). Stability tests demonstrated excellent retention rates: 92.1% thermal stability at 120°C, 94.7% salt resistance under 25,000 mg/L salinity, and 91.1% durability after 72-h flooding. Core flooding experiments showed enhanced oil recovery of 71.52% with 36.05 percentage points net increase (101.6% relative enhancement) and lowest pressure gradient (0.85 MPa/PV). Comparative studies confirmed the dual-shell design’s superiority over single-shell materials across all evaluation criteria, providing an effective approach for precision wettability control in challenging reservoir applications.