Influences of droplet volume on contact angle of reservoir rocks

The influences of droplet volume, brine salinity, liquid saturating rocks were investigated using sessile droplet method. A specific droplet volume was attained at critical water salinity. The critical water salinity is defined to be the salinity at which the oil droplet volume has no effect on contact angle. The rock wettability increases before the critical salinity and increases after it, depending upon the droplet volume. The results show that the increase of acid number of the crude oil decreases the contact angle.