LAUSR

Abstract The study of rheological properties is one of the essential aspects in designing drilling mud and its performance in operational conditions. The adding nanoparticles and natural polymers such as starch in drilling mud is the one way for modifying rheological properties. In this research, rheological behavior of a water-based drilling mud containing starch and ZnO nanoparticles were investigated and optimized. The rheological parameters were modeled by means of power law and Bingham-plastic models, then they were analyzed using ANOVA. Initially ZnO nanoparticles were synthesized and characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Energy-dispersive X-ray spectroscopy (EDS). Experiments were arranged based upon the central composite design (CCD) and results were analyzed using response surface methodology (RSM). Experimental variables (starch percentage, percentage of nanoparticles and ultrasonic time) were studied at five levels and 17 experiments were obtained with three times repetitions in the center point. The obtained regression equations for the responses were the quadratic mathematical models. The main and interacting effects between variables were studied using the analysis of variance and 3D plots. The results revealed that, the rheological parameters were more influenced by the nanoparticles amount. The optimized values of starch, nanoparticle and ultrasonic time variables were obtained equal to 0.82% (wt.), 0.2% (wt.) and 65.0 (min), respectively.