Real-Time Drilling Insights: Synchronous Bit Bounce for Cutter Failure Prediction

Abstract As the wells become more complex, identifying the locations of critical bit wear becomes increasingly difficult. The analytical models currently used in the drilling industry are not capable of completely realizing the downhole dynamics and thus incapable of bit bounce estimation and thus the bit damage prediction. This paper proposes a new mathematical model that estimates bit bounces both during critical speeds as well as non-critical speeds. This study focuses on harnessing real time downhole dynamics on drilling parameters to predict cutter failure using adaptive bit bounce and vertical shear force estimation. The adverse effects of bit-bounce on drillstring and bit performance are addressed in this study, with a focus on its correlation with axial and torsional excitation. The energy approach is employed to formulate the drillstring's motion equation, subsequently discretized using the finite element method with forced frequency response. The paper comprehensively models bit-rock interaction and impact-friction between the drillstring and borehole wall. A fully coupled vibration model developed, incorporating gravity, fluid-structure interaction, impact-friction, and bit-rock contact in the numerical model is used. Dynamic drillstring behavior is influenced by both axial and torsional excitation, with adaptable boundary conditions modeled at both the top of the string and the bit to extract the axial movement of the bit. The study's findings underscore the significant influence of both axial and torsional effects on the dynamic behavior of the drillstring and bit in particular. It has been found that, as axial and torsional excitations develop, the study estimates the amplitude and intensity of bit-bounce, analyzing the impact load on the cutters. As expected, the axial velocity reaches its peak at critical speeds and subsequently decreases. Establishing a no bit-bounce zone enables bracketing to reduce axial shear force on the cutters. The bit's upward velocity depends on rotation speed and excitation frequency. Additionally, it has been found that the reverse displacement occurs, briefly manifesting a minor reverse displacement. Consequently, evaluating bit-bounce solely based on axial velocity is cautioned. The bounce amplitude of axial displacement decreases as axial load increases, and it is noted that bit-bounce's power diminishes. Furthermore, as rotational speed increases, the bit's bounce distance contracts. Model findings, compared with actual data, indicate that bit-bounce strength decreases with increased weight on bit. Suppressing bit-bounce is achievable by applying greater bit rotational velocity and axial load within a suitable range.