Wettability alterations due to an oil soluble additive

Wettability tests were performed using Berea sandstone, NaCl brine, and n-decane with different concentrations of hexadecylamine. The tests were performed on cores both with and without initial water. Adsorption tests of the additive have also been performed on crushed Berea sandstone. It was shown that it is possible to modify the wetting properties from water-wet to neutral by the addition of a small amount of hexadecylamine. This is most likely due to adsorption of the additive on the rock surface. The resulting wetting properties were observed to be dependent on the concentration of the additive, and the effect of the additive is higher for cores not having any initial water. It was also observed that both residual oil saturation and irreducible water saturation decrease when the cores approach neutral wetting properties. This could be due to the formation of two continuous phases through the cores and less capillary trapping. The adsorption results show an increasing adsorption with increasing concentration, and the amount of adsorption for dry sandstone is twice the amount of initially water-saturated sandstone.