Experimental investigation of mechanisms influencing friction coefficient between lost circulation materials and shale rocks

Abstract The friction coefficient of lost circulating materials (LCMs) and rock is a key parameter to determine the stability of the plugging zone in the lost circulation control. However, the influencing mechanisms of the friction coefficient remain unclear. In this work, factors influencing the coefficient were studied via investigating tribological properties. To conclude, the friction coefficient increases with the normal force and decreases as the sliding velocity increasing. Tested lubricating fluids can all reduce friction coefficients, but white oil reduces more. The long-term alkali erosion can also lower friction coefficients. Friction coefficients increase with declinations of sphericity, but with the increase of surface roughness and size. Additionally, auxiliary materials (rubber particles and fibers) can increase the friction coefficient, but this increase effect is weakened under white oil lubrication. This work will reveal the conditions to maximize friction coefficient for the lost circulation control.