Effect of CO2 phase on contact angle in oil-wet and water-wet pores

Abstract Pore wetting is a principal factor in CO 2 storage, enhanced oil recovery and fuel cells. However, few measurements were directly carried in a small pore. In this study, we measured the contact angles of CO 2 –fluids systems in single capillaries, by considering effect of CO 2 phase. The liquids used are deionized water, n-decane and brine. FEP (Fluorinated Ethylene Propylene) and glass capillaries were used to represent oil-wet pores and water-wet pores, respectively. In an oil-wet pore (FEP), CO 2 –fluids contact angles vary significantly with CO 2 phase: θ gas CO 2 θ supercritical CO 2 θ liquid CO 2 . The contact angles mainly changes at CO 2 phase transition boundary. The contact angles of CO 2 –water and CO 2 –brine systems increase from 120° to 155°, and CO 2 –decane contact angles increase from 28° to 38°, when CO 2 phase changes from gas to liquid or supercritical. CO 2 –brine contact angles are close to CO 2 –water contact angles: θ brine  ≈  θ water . Comparatively, in a water-wet pore (glass), the CO 2 –fluid contact angles in a glass pore do not significantly vary with CO 2 phase: θ gas CO 2 ≈ θ supercritical CO 2 ≈ θ liquid CO 2 . The contact angles of CO 2 –water, CO 2 –brine and CO 2 –decane systems stay approximately around 30°, 40° and 26°, respectively. Moreover, the salinity does affect the CO 2 –water/brine–glass pore contact angle; θ brine  >  θ water in a glass pore.