Evaluation of lubricants used in water-based drilling fluids

The success of any drilling operation is heavily dependent on the choice of drilling fluid being used, it is essential that the drilling fluid be able to reduce bit wear, torque and drag. While drilling with oil-based mud offers less torque and drag, water-based drilling muds are environmentally safe and less costly compared to oil-based and synthetic-based muds. They also produce high friction between the drill string and wellbore.;The use of drilling fluids alone is not sufficient to reduce friction substantially, so a suitable lubricant has to be added to the drilling fluid so as to reduce the friction to an acceptable range. The lubricant reduces friction by producing a thin film of liquid that separates the solid surfaces in contact.;The primary objective of the research is to evaluate the performance of seven polymer lubricants from different vendors and also determine if the addition of nano-particles to the polymer lubricant improves the lubricity. The lubricants were evaluated using a water-based drilling mud composed of lubricants with concentrations of 0.25%, 0.5%,1%,1.5% and 2.5% by volume. The experiment was carried out in a standard lubricity meter made by Baroid. The lubricity meter tests the ability of the lubricant in the drilling mud to reduce friction using parameters that imitate torque and drag produced by the fluid downhole.;The formulations prepared were tested for torque reduction and all the lubricants studied lowered the coefficient of friction and showed significant torque reduction. The top performing lubricant among all seven was Polymer-X which produced the highest torque reduction. Higher concentration of lubricant further lowered the coefficient of friction and improved lubricity. However, some of the lubricants showed little improvement in torque reduction and started leveling off beyond a concentration of 0.5%. Addition of nano-particles to Ultralube II showed significant improvement in its lubricity.