Optimization of PDC Drill Bit Performance Utilizing High-Speed, Real-Time Downhole Data Acquired Under a Cooperative Research and Development Agreement

Abstract

Abstract PDC drill bit performance has been greatly improved over the past three decades by innovations in bit design and how these designs are applied. The next leap forward is most likely to come from using high-speed, real-time downhole data to optimize the performance of these sophisticated bits on an application-by-application basis. By effectively managing conditions of lateral, axial and torsional acceleration, damage to cutting structures can be minimized for improved penetration rates. Avoiding these damaging vibrations is essential to increasing bit durability and improving overall drilling economics. This paper describes one set of independent drilling optimization results obtained as part of a series of controlled demonstrations of PDC bits. Sandia National Laboratories on behalf of the U. S. Department of Energy (DOE) managed this work. The effort was organized as a Cooperative Research and Development Agreement (CRADA) established between Sandia and four bit manufacturers with DOE funding and in-kind contributions by the industry partners. The goal of this CRADA was to demonstrate drag bit performance in formations with degrees of hardness typical of those encountered while drilling geothermal wells. The test results indicate that the surface weight-on-bit (WOB), revolutions per minute (RPM) and torque readings traditionally used to guide adjustments in the drilling parameters do not always provide the true picture of what is really taking place at the bit. Instead, a holistic approach combining traditional methods of optimization together with high-speed, real-time data enables far better decisions for improving bit performance and avoiding damaging situations that may have otherwise gone unnoticed. Introduction Sandia National Laboratories established a CRADA between four industry partners, including ReedHycalog. The goal of the CRADA was to demonstrate drag bit ROP and durability performance improvements in hard-rock applications. To achieve this objective, ReedHycalog adopted a holistic approach that involved bit modeling analysis and design for maximum durability and dynamic stability of the cutting structure, hydraulic optimization, rock strength analysis, high-performance thermally stable cutter technology and full-scale laboratory testing. The Diagnostics-While-Drilling (DWD) system developed by Sandia National Laboratories was utilized,1,2,3 to support this work and illustrate the optimization of bit performance with real-time decision-making data. The DWD enabled the transmission of real-time data from immediately behind the bit. Data included lateral, axial and angular accelerations, WOB, bit torque, bending, internal and external pressure and temperature, and system diagnostic data. The real-time data was transmitted to the surface via wireline at approximately 200,000 bits per second (BPS), compared to the existing mud pulse telemetry capacity of only 8–16 BPS. It is anticipated that other data links will be made available in the near future including wired pipe.4 Phase 3 Drilling Outline. This final phase of the CRADA project allowed each drill bit manufacturer to demonstrate its "best-effort" bit design. Phases 1 and 2 involved the characterization of performance for a baseline drag bit; initially without real-time, downhole data feedback for drilling control (Phase 1) and later with downhole data feedback (Phase 2) to optimize bit performance with the aid of an experienced drilling engineer.5,6 The data sets from these earlier phases, which contained both surface and downhole information, were provided to each bit company for analysis prior to Phase 3. These earlier phases will not be discussed in detail except for comparison with the final phase of the project.