Numerical Simulation of the Drillstring-in-Hole Dynamics at Rotary Drilling

A numerical solution is suggested for the problem of drillstring buckling under the action of compressive load, torque and drillstring rotation in a hole of an arbitrary axial line. This problem is of great practical importance when assessing the pass ability and wear of drillstring. The developed 3D dynamic model of drillstring-in-hole and numerical solution of the problem provide a means to analyze stress-deformed state of the drillstring in contact with the wellbore. The model of normal contact force is based on nonlinear dependence of the contact force on the depth of interpenetration of bodies. The tangential contact is described using a model of modified Coulomb friction. The model of transition of sliding friction to rolling friction is suggested to take account of the effect of drillstring planetary motion. The set of partial differential equations is solved numerically based on the method of lines. A number of examples are presented to analyze the drillstring motion under the action of compressive load, torque and angular velocity, and other parameters.