Technology Focus: Bits and Bottomhole Assemblies (December 2025)

_ Picturing the “perfect well,” one is likely to think of single-trip bit runs for each section. Smooth and continuous flow of operations: connection, pick-up, back to bottom, drill a stand-down, and then the next connection. “Like clockwork,” although we don’t use that kind of clock anymore. If it were only that simple. In reality, our drilling process is punctuated with discontinuous events that can disrupt the operational flow of the perfect well. Three papers have been selected to provide insights into some of these nonstationary processes that cause bit runs to fall short of perfection. In paper SPE/IADC 223695, the authors describe two common issues during connections. Picking up off bottom without drilling off the weight or differential pressure can cause rapid torsional acceleration at the bottomhole assembly (BHA). Leaving the bit on bottom during the connection also can lead to overspeed events as the torque required to break friction is suddenly released when drilling is restarted. Although such events may be brief, not paying adequate attention to them may cause twistoffs and downhole tool failures, resulting in costly remediation. In paper SPE 220789, the authors provide a detailed explanation of the changes in polycrystalline diamond compact drill-bit cutter loading for soft-to-hard and hard-to-soft transitions, for both weight-on-bit and rate-of-penetration (ROP) control modes. Charts illustrate cutter loading in these dynamic transitions at various locations on the bit from the cone to the shoulder. The role of depth-of-cut control elements on the bit is discussed in the context of reducing cutter loads in transitions, particularly for hard-to-soft transitions. It is noted that peak cutter loads may exist for only a few seconds, so this phenomenon is not possible to control from surface. A possible outcome of not properly handling transitions is sufficient cutter damage to cause severe loss of ROP and a subsequent bit trip. In paper 224876, the authors describe a methodology to identify a pressure-loss event and possibly its root cause using a real-time machine-learning approach. Examples include washouts in the drillpipe body, drillpipe connection, mud motors, and BHA connections. In one example, two pressure-loss indications were flagged in less than an hour, with no action taken. After nine “quiet” hours, additional warning signs began, causing the operator to take action and trip out. It was found that a connection failure was progressing. If operations had continued, downhole failure was certain. Rapid identification of pressure-loss events can lead to recovery without downhole failure. As Mark Twain said, “It ain’t what you don’t know that gets you into trouble. It’s what you know for sure that just ain’t so.” It may be worthwhile to pause and think about whether events such as those described in the referenced papers may be disrupting your “perfect well.” Summarized Papers in This December 2025 Issue SPE 223695 - Study Explores BHA Damage Caused by Trapped Torque During Drillpipe Connection by Aaron Simon, SPE, and Denis Li, SPE, SLB. SPE 220789 - Modeling Approach Mitigates Premature PDC Failure in Transitional Drilling by Paul E. Pastusek, SPE, Pastusek and Associates; Mason M. Cherry, SPE, SLB; and Gregory S. Payette, SPE, ExxonMobil, et al. SPE 224876 - Machine Learning Helps Flag Abnormal Pressure Loss in Real Time by Jonathan Cortez, Michael Yi, and Dongyoung Yoon, SPE, Intellicess, et al. Recommended Additional Reading at OnePetro: www.onepetro.org. SPE/IADC 223747 - Near-Bit High-Frequency Torsional Oscillation Damper Enables Significant Drilling Performance Increase in Global Case Study by Andreas Hohl, Baker Hughes, et al. SPE/IADC 223746 - Analysis of the Efficiency of a Vibration-Mitigation Tool Using Modeling and Downhole Measurements by K.L. Nguyen, Helmerich and Payne, et al. SPE 224929 - Assessing the Impact of a Novel Vibration-Mitigation Technology: Results From Abu Dhabi Offshore Trials by A. Wahyudi, NOV, et al.