Effect of ester based lubricant SMJH-1 on the lubricity properties of water based drilling fluid

The lubricity properties of sodium montmorillonite (Na-MMT) base mud with and without lubricant were evaluated, and the lubrication mechanisms were deduced by infrared spectrum, contact angle, surface roughness and zeta potential measurement. The hydration and the increase of electrostatic repulsion between Na-MMT particles are benefit to the decrease of friction coefficient. While in the presence of lubricant SMJH-1, a boundary lubricant film exhibits relatively weak friction force compared with the lubricant-free systems. With the increase of SMJH-1 concentration, the decline of average roughness and the formation of C=S–metal film bond between the convex–concave ring–block surfaces is contributed to the decrease of lubricity coefficient. On the basis of these lubrication effects, the reduction percentage for the before and after aging base mud with 1.0% SMJH-1 reached to 91.4% and 90.7%, respectively.