A cationic type long-lasting drag-reduction agent based on reduced interfacial water film thickness for enhanced injection in low-permeability reservoirs

In water injection development of low-permeability reservoirs, the elevated flow resistance between the rock surface and the injected water results in enhanced injection pressure. Reducing the thickness of interfacial water film to expand flow radius is a new thought to achieve a decrease in injection pressure. In this work, a hydroxyl-containing cationic surfactant tetradecyl methyl dihydroxy-ethyl ammonium bromide (HTTAB) was designed and synthesized. The introduction of hydroxyl groups enhances the binding to the negatively-charged rock surface. HTTAB can modify the strong hydrophilic rock surface to a hydrophobic state, with the water contact angle increasing from 20.2° to 110.3°. HTTAB shows excellent drag-reducing effect, maintaining a drag reduction rate of over 30 % even after 30 PV of flushing. Particle Image Velocimetry (PIV) experiments show that after HTTAB adsorption, the interfacial slip velocity and centerline velocity can increase by 1.67 times and 33.66 % respectively, and the flow radius expands significantly. In addition, the thickness of the interfacial water film is obtained using Atomic Force Microscope (AFM). The results show that the thickness of the interfacial water film is reduced significantly from 79.42 nm to 8.85 nm. This study provides important guidance for the design of drag-reducing agents and the understanding of interfacial drag-reduction behavior.