Abstract
During riserless drilling operations conducted in some scientific drillings and the initial stages of all oil and gas drilling operations, drill pipe motions such as vortex induced vibration, whirl motion, and motion due to the Magnus effect are generated. The last motion represents an interesting and important phenomenon that generates a lift force in addition to a drag force due to the ocean current and the rotation of the drill pipe. Accordingly, this study focuses on the drill pipe motions owing to the Magnus effect.
An analytical model of a drill pipe was established by applying an absolute nodal coordinate formulation (ANCF) that can capture the behavior of a relatively flexible and long pipe, such as a drill pipe. The lifting and drag forces are calculated using computational fluid dynamics (CFD), and the lift and drag coefficients are calculated for several different drill pipe rotational velocities and ocean current velocities.
A series of model experiments were conducted in a towing tank, with changing water flow velocities and rotational speed of the drill pipe model to observe the corresponding changes in the Magnus effect and to measure the resulting drill pipe motions. Additionally, the resulting drag and lift forces were measured. It was observed from the experiments that the motions in the cross-flow direction increased as the rotational speed of the drill pipe model increased, and that the lifting force increased as the rotational speed increased.
The drill pipe motions were then simulated using a previously established analytical model and the results of the CFD simulations. The results of the simulations were evaluated against the results of the experiments, and reasons for observed discrepancies are discussed.
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