New Bit Design, Cutter Technology Extend PDC Applications to Hard Rock Drilling

Abstract An advanced series of PDC drill bits incorporating a new highly abrasion-resistant PDC cutter has extended effective PDC bit application to hard rock drilling. In direct offset comparisons, the advanced series of PDC bits fitted with the new cutters delivered significant increases in footage drilled and rate of penetration. To achieve an optimum match in drilling efficiency and bit life to lower costs and mitigate risk in hard rock environments, the series is designed using a combination of advanced modeling capabilities and sophisticated analytical tools. These tools allow the designs to be "customized" for specific applications, optimizing cutting efficiency and durability according to specific rock properties and drilling parameters. A transitional drilling model simulation allows evaluation of how cutting forces are affected during transitional drilling, common in "hard rock" environments. The bit design is globally balanced to optimize axial, lateral, and torsional forces, and can be modified by adjusting features such as profile shape, cutter rake angles, impact arrestors, and cutter type, to optimize bit performance when drilling in hard and transitional environments. In addition, recognition of a third dimension of PDC performance – Thermal Mechanical Integrity (TMI) -- has lead to development of a new PDC cutter that provides 13.5 times the abrasion resistance of the industry standard, without sacrificing impact resistance. This improved understanding of PDC cutter failure provides a different way of looking at the traditional characteristics of abrasion and impact, enabling cutter durability to be optimized in both abrasive and hard, inter-bedded formations. The paper discusses the science behind the advanced series of bits, including the impact of TMI on cutter performance. New laboratory capabilities and testing results are described, and actual field case histories presented to demonstrate performance improvements of these PDC bits in hard rock applications.