The effect of pressure on contact angles and wettability in the mica/water/n-decane system and the calcite+stearic acid/water/n-decane system

A new contact angle set-up to conduct experiments at elevated pressures is presented. A comparison between the practical use of the old set-up and the new set-up is discussed. The effect of pressure on contact angles in the mica/water/n-decane system is studied using the old set-up, the calcite+stearic acid/water/n-decane system is studied using the new set-up. The results indicate that the effects of the pressure on the contact angles are small for these systems. The presence of water has a positive effect on the adsorption of the dissolved stearic acid in n-decane on the calcite. This may be explained by the change of the surface charge of the calcite, which is in contact with the water. As the water contacts the calcite surface, dissolution of calcite takes place, hence dissociation of stearic acid in the n-decane/water interface occurs leading to a chemisorption reaction at the surface of the calcite where calcium stearate is formed. This interns converts the calcium surface to a strong oil wet.