Experimental Study on Stuck Pipe Release by BHA Whirling

Differential pressure sticking (DPS) is one of the most common causes of pipe sticking when a drill-string rests on a borehole wall or even is submerged into a mud cake [1]. Differential sticking can significantly impact the cost of wells and non-productive time for the rig and usually harms the environment, particularly if the BHA has to be abandoned downhole. Failure to free a drill-string leads to significant financial losses due to contractual charges, time-consuming interventions, hole abandonment, side track requirements, environmental problems and others. The existing technology can apply only a limited axial force and jarring load to the stuck object. Thus, a new method should be developed and employed to release differentially stuck pipe problems. To overcome DPS, a concept of the "Advanced Shock Tool" was proposed by Saudi Aramco in the patent US2019368295 [2]. The idea of this tool stems from generating periodic or chaotic lateral loads on the stuck point rather than applying conventional methods, subjecting the stuck point to axial impact loading only. The expectation is to generate these additional forces by applying torque on the asymmetric pipe section above the stuck point, with under-gauged stabilisers and a rotary tool disconnecting torque transmission from the stuck point. To address the above-discussed challenge of a differentially stuck pipe, a large-scale experimental rig was designed, manufactured, installed and instrumented to investigate the whirling motion of a shaft interacting with housing to mimic the new jarring method introduced earlier. This experimental study focuses on generating large lateral vibration by developing a robust backward whirling motion, examining the possibility of generating and sustaining such dynamical responses for a wide range of parameters, and ultimately proving the concept of the Advanced Shock Tool in a large-scale experimental setup. The following sections describe the developed experimental setup, experimental strategy and the main results.