PDC Bit with Industry's Largest Cutter Achieves Breakthrough Performance and Savings in Kuwait
Authors: Grimes Bobby , Omar Marwa , Lee Roger , Mayyan H. Al , Sharhan A. Al , Malik A. 
Published: March 2017

In the current challenging global oil and gas market, operators strive to minimize cost-per-foot (CPF) through drilling optimization and the introduction of next-generation tools to maximize return-on-investment. In response, service companies seek game-changing solutions to enhance operators' drilling operations. A cross-functional optimization team was chartered to enhance rate of penetration (ROP) in development drilling Kuwait's prolific Burgan field. The team developed a polycrystalline diamond compact (PDC) drill bit design with 25mm (1 in.) PDC cutters –presently the largest diameter commercial cutter in the industry. This paper presents the outstanding field results that were achieved with the 25mm cutter bit design. The analytical and experimental processes used in the development of the bit design will be described, and the operational results and resulting savings will be presented and compared to the established field benchmark.

The geology of the 12¼ in. intermediate sections of Burgan wells is comprised of layered carbonates, shales and sandstones. The section is known to induce moderate-to-severe torsional vibrations with conventional rotary bottomhole assemblies through the heterogeneous formations. Operational practices to mitigate these vibrations effectively limit the section ROP. To address this challenge, an optimization process was initiated to manage the problematic vibrations and maximize drilling efficiency through bit design and cutter technology.

In an application that was long dominated by conventional PDC bit designs with 19mm cutters, an upgraded 25mm cutter with the latest HP/HT pressing technologies incorporated in a tailored bit design to strike a balance between drilling aggressiveness and vibration control. The large cutter's unique depth-of-cut potential and increased cutter exposure were combined with reduced bit imbalance and degree of rubbing via numerous computerized simulations as part of the analysis for the Burgan application. The 25mm cutters were lab-tested and video-recorded on a dedicated laboratory rock mill to evaluate the ROP potential and apply these concepts to the 25mm cutter bit design. After the experimental bit was manufactured and performance tested in a controlled laboratory environment, the engineering team focused closely on the successful execution of the preliminary field trials, and then evaluated the results.

Deployment of the engineered 25mm cutter bit design led to multiple breakthrough performances in consecutive bit runs, achieving 300%+ increased ROP on each deployment compared to the established 12¼ in. field average. Analysis of the drilling logs indicates the engineered bit design provided the highest drilling efficiency to date in comparison to all conventional PDC bits previously run in this application. Torsional variations were limited through the interbedded formations, which allowed drilling parameters to be optimized throughout the runs. As a result, the operator reduced rotating hours by 70% vs. the field benchmark, with a corresponding 30%+ reduction in CPF.