THE INFLUENCE OF INTERFACIAL POTENTIAL ON FRICTION AND WEAR IN AN AQUEOUS DRILLING MUD

Aqueous drilling muds, whilst recognised as environmentally benign, gi ve higher coefficients of friction than their oil-based counterparts, leading to increased torque and drag on the drillstring. This work con cerns a novel approach to improving the lubricity of aqueous drilling muds, namely by controlling the electrochemical potential at the drill string-drilling mud interface. A Cameron-Plint high-frequency friction machine, modified to accept an electrochemical cell, has been used to measure friction and wear in aqueous drilling muds for mild steel pin s rubbing on mild steel or sandstone wear plates. It was found that th e coefficient of friction at metal-rock contacts decreased on applicat ion of a cathodic potential, whilst friction at metal-metal contacts d ecreased when an anodic potential was applied.