Non-aqueous drilling fluids (NADF) leave an oil-wet residue on the formation that prevents cement from bonding. Spacers are often used to clean the formation surface before a cementing operation begins. Evaluating a spacer’s ability to convert an oil-wet surface to water wet is necessary to ensure proper cement bonding.
The Advanced Digital Wettability Tester uses electrical resistance to determine the effects of adding water-wet spacers to oil-wet NADF. An overhead mixing blade stirs the fluid while electrodes measure resistance and temperature. As spacer is added, the change in resistance is graphed and recorded. This allows the user to compare the effectiveness of different spacers with different NADF.