A COUPLED FLUID-STRUCTURE MODEL FOR ESTIMATION OF HYDRAULIC FORCES ON THE DRILL-PIPES

Most models employed for fluid forces in drill-string dynamics are of reduced order. The simplified nature of these models often fails to describe complex behaviour of the fluid force, in particular when the drill-string movement is non-trivial or even when non-Newtonian behaviour is predominant. In this work, the fluid forces are estimated by modelling the dynamic of the drilling fluid for both Newtonian and non-Newtonian fluids, and compared with reduced order models. To achieve it, the lattice Boltzmann method is implemented to solve the fluid model, while prescribed movements are set for the tool-joint. With the obtained fields, the forces are calculated and compared with recurrent models. Finally, it is observed that some models are capable of describing the interaction as long as the dynamic of the tool-joint is simple. In the presence of other trajectories – e.g.: bouncing and chaotic – the models fail to describe the details of the dynamic.