Computer Modelling of Drill String of an Oilwell Drilling Rig

The article considers the questions of construction and computer realization of the mathematical model of drill string of a drilling rig. An approximation model is proposed in the form of systems of ordinary differential equations. Built on their basis, the computer model of the drill string has several important properties: allows you to reproduce the change of physical parameters in the sections of the drill string; reproduce nonlinear dependencies; the model is reversible, which makes it possible to implement incoming influences and receive feedback at the level of any structural element of the model. The proposed model allows to take into account: heterogeneity of the drill string with the use of different types of drill pipes; deformation of the drill tower under load and its inertia; resistance forces caused by the interaction of the washing liquid with the walls of the column; action of pushing force, as well as inertia of the washing liquid; the strength of the resistance when the drill bit is interacting with the rock; flow of energy during the rotational and translational motion of the drill string due to the rolling of roller cone. The given modelling results indicate that the obtained model can be successfully used both at the stage of calculating of the drilling compartment layout and in the control system to maintain optimal drilling modes while drilling, as well as to optimize descent-lifting operations.