Using Taguchi and ANOVA methods to study the combined effects of drilling parameters on dynamic barite sag

• The Taguchi method in conjunction with ANOVA can be used to quantitatively study barite sag.
• Annular velocity has the most significant impact on preventing barite sag.
• Inclination angles in the range from 45° to 60° have a very minimal effect on preventing sag.
• Drill-pipe rotation and eccentricity contribute 21% and 15%, respectively, to prevent sag.

The settling of barite particles in drilling fluids under no-flow conditions and under flow conditions is still a major problem in drilling. The separation of barite particles out of the drilling fluids causes a variety of problems, such as stuck pipe, lost circulation, and poor cement jobs. Furthermore, several severe well-controlled incidents have been caused by barite sag.This paper presents the quantitatively combined effects of the drilling parameters on dynamic barite sag in oil-based drilling fluids. The drilling parameters include annular velocity, pipe rotation, inclination angle, and eccentricity. Two levels for each parameter were considered to develop the test matrix in this study. For example, the parameter of inclination angle has two levels including concentric drill pipe (e=0) and eccentric drill pipe (e=1). The Barite Sag Flow Loop (BSFL), which utilized a coriolis mass flow meter to measure the circulating density of the fluid, was used to conduct tests. The Taguchi method was used to design the test matrix, which greatly reduces the number of experiments required and offers the optimum settings of the control parameters. Based on the two levels of the analyzed parameters, the annular velocity and pipe rotation contribute almost 60% and 21%, respectively, to the prevention of sag. The results also indicate that changing the inclination angle in the range from 60° to 45° from the vertical has the least impact on the prevention of barite sag. The results of this study enable drillers and designers to operate and design wells with fewer problems related to barite sag.