CFD simulation and optimization of slurry erosion of PDC bits

Polycrystalline diamond compact (PDC) bits are subjected to harsh erosive conditions under downhole. The erosion resistance partly determines the rate of penetration and footage of the bit. This work aims to investigate the effects of key factors on the erosion resistance of PDC bits through numerical simulation and field trials, and then to optimize the bit hydraulic designs. Computational Fluid Dynamics (CFD) and Discrete Phase Model (DPM) model were used to simulate the evacuation and impingement of cuttings on the bit body at the bottom of the well. The reliability of the numerical simulation was verified by the bit conditions after the field testing. Fuzzy grey relational analysis (FGRA) was then employed to rank the correlation degree of various affecting factors. The FGRA results show that the mass flow rate has the greatest effect on the average erosion rate of PDC bits, followed by the flow rate. The most erosion-vulnerable areas on the bit body are the webbings between cutters as well as the blade front. To improve the erosion resistance from the perspective of the bit hydraulic design, three novel hydraulic structures were proposed: the optimized nozzle orientation, the multi-ridge guide, and the extended curved nozzle. Numerical simulations indicate that all of these novel designs have great potential to enhance the erosion resistance of PDC bits with the customized extended curved nozzle showing the best.