Compositional dependence of wetting and contact angles in solid-liquid-liquid systems under realistic environments

The wetting and contact angles in porous media are important for the characterization of multi-phase flow behavior. The polar components such as asphaltenes in the oil-phase, which have been widely believed to be a major source of oil-wetting characteristics. The effect of light gaseous ends in crude oil on wetting is studied by depleting the pressure at regular intervals. The variation of contact angles observed with the pressure during the pressure depletion clearly showed the influence of light ends on wetting. The water-advancing contact angle of live crude oil gradually increased from 55° at bubble point pressure to 154° at ambient pressure. The de-asphaltened and the deresined crude oils showed strong oil-wet characteristics as stocktank crude oil. The light gaseous ends in oil phase appear to peptize the asphaltene molecules by surrounding them, thereby preventing their agglomeration and migration to the interface. The differences observed in the behavior of dynamic interfacial tensions between live and stocktank crude oils further substantiates the influence of light gaseous ends on the activity of polar components in live oil. The influence of solid surface roughness, mineralogy of rock substrates as well as the brine composition on wetting and contact angles have also been investigated. For highly smooth substrates, carbonate and silica showed relatively similar high water-advancing contact angles, while for rough substrates, the advancing contact angles on silica were much lower compared to the carbonates.