Experimental analysis of drillstring vibrations using a small-scale drilling rig

Abstract As global demand for energy continues to increase, the optimisation of oil and gas drilling being the largest energy source is essential to reducing global warming and environmental impact. This often includes minimising and avoiding undesired vibration phenomena which significantly contribute to drilling efficiency, borehole integrity, and drilling accessories lifespan, all of which contribute to the overall environmental footprint. This study aims to experimentally investigate and analyse a detection approach for these phenomena including bit bounce, whirling, and stick–slip. An experimental rig setup has been specifically designed in this work to explore the factors affecting drilling performance and investigate the occurrence of those undesired vibrations. These factors involve the manipulation of different drill-bit parameters such as its loading rate or weight on bit, its speed in terms of revolution per minute, its cutting teeth configurations, and its drilled surface condition based on the presence or absence of drilled cuttings (clean or unclean) and the presence or absence of drilling fluids (wet or dry). Each of these drilling scenarios were examined experimentally using real-time monitoring and analytical techniques, including bivariate kernel estimation, spectrum analysis, and periodogram analysis, for evaluating the dynamical behaviour of the drillstring and analysing its impact on drilling performance. The findings revealed that carefully selected (optimised) drilling parameters effectively enhanced the rate of penetration at higher loading rates under certain conditions, despite the exacerbated vibrational effects during the higher drilling speed. Also, the performance of the bit was seen to be significantly affected by the configuration of its cutting teeth. Results highlighting the complex behaviour between operational parameters and the drillstring’s exhibited dynamics have also been presented. Overall, the study presents an extensive understanding of the relationship between drillstring dynamics and drilling performance, facilitating practical strategies of mitigating the occurrence of undesired drillstring dynamics, ensuring more efficient and safer drilling processes.