Tailored Solution for Mitigating PDC Bit Balling Challenges in Drilling Sticky Shale

Abstract Drilling in sticky shale formations presents a tough challenge due to bit balling, where traditional solutions such as oil-based mud not only strain finances but also harm the environment. Conversely, while water-based mud offers a more economical alternative, it increases the risk of bit balling, resulting in frequent bit trips and reduced rates of penetration (ROP), thereby escalating overall well costs. To combat the risk of bit balling in water-based mud, the focus must be directed towards three pivotal factors: 1. suitable drilling mud composition, 2. appropriate drill bit design, and 3. proper drilling parameters. Neglecting any of these elements can lead to decreased ROP and increased bit trips. This paper will focus on the design features of PDC drill bits tailored specifically to address PDC bit-balling challenges, such as effectively evacuating cuttings from the cutter's face out of the junk slots and providing sufficient space on the bit face to avoid creating formation cuttings lumps. Two key features crucial for addressing these challenges in PDC drill bits are: 1. optimizing bit face volume and 2. hydraulic enhancement through computational fluid dynamics (CFD). A pioneering approach utilizing CFD optimization has been devised to customize fluid distribution based on the displacement of the formation by each cutter. This innovative technique ensures that cutters exerting greater work on the formation receive proportionately higher fluid volumes, effectively mitigating bit balling. Additionally, the study examines the optimization of PDC bit face volume without compromising diamond volume. Test conducted on a bit design employing these methodologies yielded promising results, affirming their ability to overcome bit-balling challenges.