To reduce cost, drilling operations are getting longer, both in time and distance. Simultaneously, drilling parameters are optimized to reach higher performance for a maximum rate of penetration (ROP). The drawbacks of these practices are increased static and dynamic loads such as bending stresses, torque, and vibration on the drilling system. These parameters can greatly fatigue even the most robust drilling tools. Downhole drilling dynamics services must be used to ensure reliable operation with optimum performance.
This paper discusses the general challenge to balance reliability and performance. For this process, tools are needed to measure the respective downhole data. A database is required to help connect downhole dynamics data and surface data like drilling parameters such as weight on bit and rotary speed, with context data such as geological formation and system reliability. To analyze dependencies and optimization approaches, it is necessary to review the data in various ways and from different perspectives through the data sets. This review can be achieved by using crossplots in various dimensions.
The recording of downhole data with sampling rates exceeding 1000Hz and subsequent analysis of high-frequency drilling data provide insight into the excitation mechanism for vibrations. Additional statistical analysis of the data reveals the true load profile on the drilling system and its origin, enabling optimization in two ways. The tool or system design is optimized for reliability considering the identified loads, and the loads are minimized by optimizing the drilling parameters. Novel modeling techniques enable estimation of the dynamics load distribution over the bottomhole assembly (BHA), even from a single measurement position. Analysis shows that the main dynamic loads stressing the system are lateral vibrations and high-frequency torsional oscillations. Temperature effects also play a significant role for electronics. Statistical models support the decisions to retire tools or components and any re-run decision.
The use of drilling dynamics services and the real-time downhole data ensure informed decisions during the drilling process, optimized performance by minimizing loads on the system, and maximized ROP with optimal drilling parameters. The collected downhole data, in combination with context data and reliability data applied in the design process, lead to fit-for-purpose designs of the latest drilling tools.