The industry trend to drill wells faster and with greater precision in hard, dense, difficult to drill formations results in challenging drilling dynamics conditions. In particular, high-frequency torsional oscillations (HFTO) occur in such drilling situations. This kind of vibration creates loads that can quickly lead to fatigue or electronics damage, which translates into non-productive time (NPT) and cost.
There have been different approaches proposed to mitigate vibrations or design tools that withstand these vibrations. This paper presents a new generation rotary steerable bottom hole assembly (BHA) system specifically designed for extreme drilling dynamics conditions. Field tests and field applications demonstrate the new level of performance.
The cutting process in hard and dense formations triggers the occurrence of HFTO. In the design process, emphasis is on fatigue performance to optimize tools and their components, particularly with respect to torsional resonances in the HFTO frequency range of 100 Hz to 500 Hz.
General reduction of vibration loads uses integration of mechanical isolation and damping principles with a rugged design. Different design options are first modeled, simulated, and optimized. Tests validate the best design against vibration requirements to prove robustness for maximum durability.
New features of the tools like downhole frequency analysis and load measurements support the pre-well BHA optimization and the real-time drilling optimization. New procedures for tool management and BHA planning use dynamics field data consequently captured and systematically evaluated with big data analytics methods.
The modeled HFTO frequencies and amplitudes agree very well with field measurements. Modeling and field tests show that the implementation of mechanical isolation concepts can protect portions of the BHA from harmful HFTO vibrations. The introduction of mechanical damping elements can reduce the occurrence of HFTO up to complete suppression, while maintaining high performance drilling parameters. Compared to previous tool generations, the new system specifically considers HFTO during design and is thus better able to withstand this kind of vibration. The design of new thread connections increases their (load) capacity over standard thread connections. The implementation of multi-chip module (MCM) electronics with the tools significantly extends the electronic lifetime and durability.
A simulation system particularly developed to optimize BHA configurations in the pre-job planning phase with respect to HFTO, analyzes various configurations to select the best fit-for-purposes BHAs. Case studies demonstrate increased reliability, utilization, and footage (more than a mile-a-day drilling), making a significant difference in the rotary steerable (RSS) market.
New mechanical isolation, damping, and MCM concepts, complemented by novel real-time downhole measurement capabilities, enable an effective, holistic approach to overcome critical drilling situations and react on HFTO events. This all new, relentlessly iterated design demonstrates superior reliability and drilling performance, maximizing customer value.
