Experimental Visualization of the Effect of Flow Rate on Downhole Drilling Vibration

Abstract Downhole drilling dynamic data has proven to be valuable operational information for vibration mitigation and drilling optimization. Yet, the downhole dynamic behavior of the BHA is often misinterpreted. Most downscaled experimental investigations neglect the changes in dynamic field conditions due to fluid flow. The objective of this work is to establish a visual understanding of downhole vibration data analysis in the presence of fully circulated fluid flow and to investigate the effect of flow rate on the BHA lateral trajectory, using a scaled laboratory BHA. A mechanically downscaled test assembly adhering to the geometric and material property relations of a field-size BHA section was designed and manufactured to investigate the nature of lateral vibration under field-like fluid flow conditions. Axial excitation and rotation were induced respectively using an electromagnetic shaker and an electrical motor. Fluid was pumped through the BHA using an electric pump and an in-house designed swivel. The BHA trajectory was mapped using inductive displacement sensors mounted outside the transparent wellbore structure for direct visual correlation between the BHA movement and the vibration data. Real-time induced bit vibration was observed and recorded using a high-frequency tri-axial accelerometer. The results from this experiment provide precise and insightful visual information for BHA trajectory correlation with the acceleration data acquired under field-like fluid flow conditions. The BHA vibration behavior of high-frequency accelerations (shock and vibration), critical lateral vibration phenomena such as whirling, and shift in dominant vibration frequencies were characterized based on both the nature of dynamic forces at the bit and fluid flow rates. Instead of a general observation of the vibration-damping effect in the presence of circulating fluid, the experiment also presents correlations between vibration characteristic changes at different frequencies for different flow rates. In conclusion, the investigation distinguishes between the dynamic relation of fluid damping of vibration and fluid-induced vibrations, both in relation to the dynamic vibration data and the downhole dynamic behavior of BHA movement. The novel experiment establishes both quantitative and qualitative relations between the observation of acceleration data and physical vibration behavior during drilling in the presence of circulating fluid. The experimental results provide clear insight not only into the dynamic nature of vibration-damping but also into fluid-induced vibrations, which affect the window of safe operating drilling conditions.