CFD modeling of the flow behavior around a PDC drill bit: effects of nano-enhanced drilling fluids on cutting transport and cooling efficiency

Abstract

ABSTRACT In the present study, hydraulic and thermal performances of nano-enhanced drilling muds have been studied across the complex geometry of a rotating polycrystalline diamond compact (PDC) drill bit using computational fluid dynamics techniques. Toward this goal, a robust converging procedure is applied to generate an advanced tetrahedral/prism grid structure using special techniques. We also utilize a combination of the realizable k-ԑ turbulence model with enhanced wall treatment and Eulerian-Lagrangian discrete phase model (DPM) to investigate the flow field and particles tracking across the bit. The results reveal that the rheological properties enhancement obtained by adding even a small quantity of nano-fluids leads to a remarkable increase in the cutting transport efficiency. According to our results, CuO and ZnO nano-enhanced muds show up to 127% and a 68% rise over the cutting transport ratio of the base fluid at the bit rotational speed of 30 rpm. Besides, the predicted temperature on tip of the bit cutters indicates that increasing the thermal conductivity of nano-enhanced muds can lead to effective cooling only in conjunction with improving rheological characteristics. CuO NWBMs show up to a 16.7% reduction in the temperature of the front surface of bit cutters over the base fluid.