Polyurethane Microcapsules Based on Microfluidic Technology for Enhanced Oil Recovery

In this study, we successfully prepared polyurethane microcapsules with regular morphology, uniform particle size and excellent monodispersity by means of microfluidic technology. The microcapsules use surfactant as the core material and polyurethane as the wall material, which significantly improves the controllability and repeatability of the traditional microcapsule preparation method. The prepared microcapsules not only have a minimum particle size of 44.5 μm, but also have a narrow particle size distribution (65–71 μm) and an average diameter of 67.4 μm, fully demonstrating excellent morphology control ability. In terms of performance evaluation, these microcapsules showed rapid targeted release characteristics in both light oil and heavy oil, especially in heavy oil, which could be completely dissolved within 10 s, indicating that they had good compatibility with oil molecules. Furthermore, the microcapsules encapsulated with AEO-3 surfactant can significantly reduce the oil–water interfacial tension from 27.68 mN·m–1 to 6.67 mN·m–1, which significantly enhances the peeling ability of oil droplets from the rock surface. In particular, when the concentration of microcapsules was 0.1 wt %, the Zeta potential of the dispersion system was −36.12 ± 0.7 mV, indicating that the system had high stability and effectively prevented the aggregation or precipitation of microcapsules. In addition, the microcapsules can maintain morphological integrity under high salt (10 wt % NaCl, 7 wt % CaCl2) and high temperature (80 °C) conditions, showing excellent temperature and pressure resistance. Microscopic oil displacement experiments show that microcapsules can effectively enhance oil recovery by reducing oil–water interfacial tension and changing rock wettability, showing its great application potential in the field of enhanced oil recovery (EOR). These research results not only verify the advantages of microfluidic technology in the preparation of microcapsules, but also provide strong support for the development of intelligent oil displacement agents.