Effect of previous sedimentation time in filtration rate for shear-thinning suspensions

Abstract

In oil well drilling, the Annular Pressure Build-up (APB) phenomena may lead to several damages in the formation and, in some cases, the well losing. Open shoes are generally used to mitigate this phenomenon, in which some spaces are maintained opened under the wall coating, at the well bottom. After the fluid expansion and pressure raising, the confined fluid flows directly to the rock formation. The sedimentation of the weighting material in the drilling mud in confined annular regions provides a thicker cake which may clog the shoe, turning the mitigation process inefficient. This research aims to study the effect of previous sedimentation and temperature on the filtrate volume and the mud cake properties for shear-thinning suspensions. To study the particles settlement, the falling dynamics were monitored by an online microscope coupled in a sedimentation test apparatus. Filtration experiments with and without previous sedimentation were performed. It was possible to conclude from experimental data that, for non-Newtonian fluids, filtration and sedimentation rates are increased with previous sedimentation. The main responsible factor is the presence of agglomerated particles vertically chained, increasing the permeability of the sedimentation cake. The observed mechanics are favorable to the annular pressure relief.