Effect of different rheological models on prediction of tri-cone bit pressure drop

Abstract

In this study, viscous, non-Newtonian turbulent flow simulations are obtained through a tri-cone bit inside a bottom hole to show the effect of different rheological models on pressure drop calculations. The rheological models include Bingham plastic, Power law, and Herschel-Bulkley. Flow simulations are obtained for nozzle sizes of 7/32, 9/32, 10/32, and 11/32 inch and four different flow rates are used in each solution. A standard water-base mud is selected for this study. Rheological data are obtained using a Fann viscometer. The calculated pressure drops from CFD simulations are then compared to experimental data and Eckel-Bielstein equation. The results show that Herschel-Bulkley model has predicted the pressure drop with the least average percent error of 5.90 as compared with experimental data. This is followed by Power law and Bingham plastic rheological models, and Eckel-Bielstein equation with the absolute average percent error of 6.64, 8.00, and 17.57, respectively. [Received: May 24, 2017; Accepted: December 1, 2017]