Study of the Hydraulic Performance of Drill Bits Using a Computational Particle-Tracking Method

Abstract

Summary The hydraulic performance of fixed-cutter drill bits was studied with the ANSYS-FLUENT code (ANSYS 2012). Cuttings were modeled as spherical particles that were injected from the bottom of the hole, and discrete particle modeling (DPM) was used to track the cuttings in which particle/particle interaction is ignored. The ratio of average particle velocity to average annulus fluid velocity, referred to as the cuttings-transport ratio (Ct), was then evaluated to study the hydraulic performance of drill bits under different conditions. The simulation results show that Ct increases as nozzle-jet velocity and HSI (hydraulic horsepower per square inch of bit) increase. Comparing Ct with rate-of-penetration (ROP) data available in the literature revealed that the rate of Ct change is less than that of ROP as HSI changes. Ct decreased slightly in a bit with seven nozzles when compared with the same bit with five nozzles with the same total flow area (TFA) of nozzles and inlet flow rate. Also, Ct was found to be insensitive to the nozzle-size arrangement and bit-waterway profile in the studied bit size. Overall, the current method (with the assumption of negligible particle/particle interaction) is more appropriate for predicting drill-bit hydraulic performance when drilling hard and nonreactive formations.