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

Aqueous drilling muds, whilst recognised as environmentally benign, give higher coefficients of friction than their oil-based counterparts, leading to increased torque and drag on the drillstring. This work concerns a novel approach to improving the lubricity of aqueous drilling muds, namely by controlling the electrochemical potential at the drillstring-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 pins rubbing on mild steel or sandstone wear plates. It was found that the coefficient of friction at metal-rock contacts decreased on application of a cathodic potential, whilst friction at metal-metal contacts decreased when an anodic potential was applied.