Near-Bit HFTO Damper Enables Significant Drilling Performance Increase in Global Case Study

Abstract The drilling performance of rotary steerable systems is defined by the capabilities of the surface and downhole system, the bit, the formation, different functional aspects such as hydraulics, and is limited by dysfunctions that constrain the operational parameter envelope. One such constraint is vibrations that limit the drilling efficiency and can result in premature damage of the bottom-hole assembly (BHA). High-frequency torsional oscillations (HFTO) are a particularly damaging vibration mode that cause failures at sensitive electrical and mechanical components through high acceleration and dynamic torque values. To prevent these damages, the operational parameter envelope and the bit and BHA design options are constrained which compromises the drilling performance. The paper introduces a steering unit with HFTO-damping capability which was designed to overcome these limitations. The inertia-based damper is implemented in a component of the steering unit close to the bit. The placement close to the source of the vibration enables an effective mitigation of HFTO, as suggested by theoretical considerations, simulations, and lab testing. A worldwide case study with >50 deployments covers representative applications/BHAs, environments and formations. In the case study a reduction of damaging HFTO of typically 100 % (and at least by 99 %) compared to offset runs was achieved. Third party vibration mitigation tools were significantly outperformed regarding HFTO reduction. The data confirms a significant improvement in reliability and re-run capability of the deployed BHAs. After proving the HFTO mitigation capability, the weight on bit and bit rotary speed limits were increased resulting in a significant increase of the rate of penetration (ROP). The drilling parameter increase enabled record runs in specific applications discussed in the paper. In summary, HFTO effectively disappeared with the introduced steering unit. This in turn allowed for an increase in Weight on Bit (WOB) and bit rotary speed, opening the operating parameter envelope, resulting in achieving an even higher rate of penetration. The early study proves a significant cost saving potential enabled by higher reliability, lower non-productive time, and increased drilling efficiency and ROP. The results create opportunities for the introduction of new rotary steerable designs that were previously unattainable.