Unique Range of High Performance Drill Bits with Select PDC Cutter Technology Deliver Breakthrough Performance in Specific Applications Globally
Authors: Roberts T. S. , Garcia A. , Rahmani R. , Whipple Justin 
Published: January 2016

Polycrystalline Diamond Compact (PDC) fixed cutter drill bits have provided significant breakthrough to the drilling industry by extending the boundaries from softer formations, such as shale into harder rocks, such as limestone. The emphasis of this technology is on reducing costs by drilling faster through shale formations, maintaining steerability and stability in increasingly complex wells and ensuring greater durability through abrasive sandstone or tough limestone. The combination of drill bit design and PDC cutter technology affects all of these, though performance is limited when bit balling occurs or the cutter structure suffers from overload or thermal degradation.

In an ongoing endeavor to further push the boundaries of PDC technology and Rate of Penetration (ROP) improvement, several engineering teams were formed, one focused on dynamic bit modelling to better understand the forces on the drill bit cutting structure. All aspects of the bit and assembly were considered and modelled using newly developed software, to ensure optimal performance. Another studied hydraulic design to understand bit balling and improve drilling performance. This included the effect of nozzle orientation, nozzle count and blade height as well as a new flow guide added to the blade front. Computational Fluid Dynamics (CFD) was used to hydraulically design the drill bit for shales. Following CFD simulations, experimental tests in a Pressurized Drilling Lab (PDL) were performed to validate the CFD results. A third team focused on PDC cutter technology by defining the principal failure criteria for each application and engineering a range of PDC's with the precise properties to overcome these. Following detailed laboratory tests designed to simulate downhole cutter failures, a new Cutter Index (CI) was formed. The CI ranked the cutter technology according to its resistance to three primary failure mechanisms identified: thermal degradation, abrasion, and impact damage.

The teams utilized both numerical and experimental approaches to tackle these challenges. Full scale bits were built and tested in the laboratory. The hydraulic team delivered an ROP increase of up to 35% compared to baseline bits using improved nozzle orientations and the new flow guides. The new cutter technology included specialized cutter treatments, illustrated several performance advances, the greatest in sandstone, where they demonstrated a 150% improvement in ROP during full scale testing.

By combining extensive dynamic drill bit modelling, improved hydraulics and a strong focus on the true failure mechanisms of the operation, the team was able to prove that improvements in both drill bits and cutter technology can yield breakthrough performance. Several applications clearly show the benefit of both the dynamic and hydraulic modelling and how matching the correct cutter characteristics to the application can yield a remarkable improvement in ROP. This increase in bit performance has permitted operators to drill farther and faster, resulting in significant cost savings.