Effects of porous media geometry and oil repellents on enhanced recovery in water-wet microfluidic chips

As the global energy demand grows, with oil consumption projected to reach 102.1 million barrels per day in 2024, maximizing oil extraction from known reserves has become critical. In this study, we demonstrate a preparation method for water-wet microfluidic chips and investigate two-phase flow repulsion experiments at the microscale. Four pore structures of porous media with different characteristics were designed based on the Voronoi surface subdivision algorithm, and water, surfactant, and polymer repulsion experiments were carried out at a repulsion rate of 0.2 µl/min. The results quantitatively demonstrate that increasing pore structure complexity reduces the final recovery rate, with the simplest Voronoi structure 1 achieving 81.7% recovery compared to 53.2% for the most complex Voronoi structure 4. The water injection channels overlap with the ‘dominant channels’ generated by the pore structure, with breakthrough times varying from 15.2 min for Voronoi 1 to 12.6 min for Voronoi 4. Areas with pore throats smaller than 60 μm show significantly reduced fluid penetration due to increased capillary resistance. The injection of surfactants improved recovery to 67.3% compared to 53.2% for water injection in Voronoi structure 4, primarily by reducing interfacial tension, while polymer injection achieved 62.1% recovery through improved sweep efficiency. Analysis reveals that the primary type of residual oil in these structures is ‘blind end residual oil’, formed due to the interplay of capillary forces and flow path development.