Numerical study of the nonlinear dynamics of horizontal drillings

Summary. This paper presents a model to describe the nonlinear dynamics of a drillstring in horizontal configuration, which is intended to correctly predict the three-dimensional dynamics of this complex structure. This model uses a sophisticated beam theory, with effects of rotatory inertia and shear deformation, which is capable of reproducing the large displacements that the beam undergoes. Also, it considers the effects of torsional friction and normal shock due to the transversal impacts between the rotating beam and the borehole wall, as well as, the force and the torque induced by the bit-rock interaction. This is done as a first effort to solve a robust optimization problem, which seeks to maximize the rate of penetration of the drillstring into the soil, to reduce the drilling process costs. Numerical simulations show that the dynamic behavior of the drillstring is strongly correlated with the number of shocks, which causes the column to assume complex spatial configurations, and force a reduction in the drilling process efficiency