Effects of particle-size distribution and solid additives in the apparent viscosity of drilling fluids

Abstract

The rheological behavior of drilling fluids depends on the physicochemical characteristics of viscosifying, weighting and bridging agents, such as particle size distribution, charges, chemical composition and density. The accurate controlling of the viscosity profile ensures a higher performance in the drilling process. In this work, the influence of polymers and the particle-size of barite, calcite and glass spheres in the apparent viscosity of suspensions was evaluated. Carboxymethyl cellulose (CMC) and xanthan gum (XG) dissolved in water were used as viscosifying agents. The rheological characteristics of suspensions were evaluated, as well as their zeta potential and microstructure properties. The suspensions of fine material particles presented higher values of shear stress. The CMC polymer increased apparent viscosity at more significant levels than XG and the polymer chain characteristic was predominant over the solid effect. Barite and glass spheres suspensions presented higher zeta potential and lower shear stresses values when compared to calcite suspensions which presented a stronger electrostatic interaction with polymers. Statistical tests were performed using the analysis of variance and results were validated inside 95% of confidence level.