The effect of pressure on contact angles and wettability in the mica/water/n-decane system and the calcite plus 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 m ica/water/n-decane system is studied using the old set-up, the calcite + st earic acid/water/n-decane system is studied using the new set-up. The resul ts indicate that the effects of the pressure on the contact angles are smal l for these systems. The presence of water has a positive effect on the ads orption 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 i n contact with the water. As the water contacts the calcite surface, dissol ution of calcite takes place, hence dissociation of stearic acid in the n-d ecane/water interface occurs leading to a chemisorption reaction at the sur face of the calcite where calcium stearate is formed. This interns converts the calcium surface to a strong oil wet. (C) 2000 Elsevier Science B.V. Al l rights reserved.