Mohammad Damshenas - Ms.c in Mechanical Engineering in Applied Mechanics & Design
Mohammad Taghi Ahmadian - Professor of Mechanical Engineering in Sharif University of technology, Tehran, Iran

Vibration is one of the most influential factors in the design, optimum performance and lifetime of all machinery. Analysis of the vibrations created in drill string like other fields such as rotary drilling is important and due to the length of the drill string whirling isprobably one of the most important issues that leads to reduce Penetration rate therefore increases the time and cost of drilling operation…The purpose of this article is to find the effect of variable injection of drilling mud around inclined drill string with Stick – Slipphenomenon and deformation because of whirling. For this purpose, a series of kinetic and potential energy equations for rotary drill string, considering the longitudinal and transverse vibrations plain and Lagrange method to achieve equations of motion areused.. The modeling is done by using the finite element software ANSYS™ and drill string weight and the effect of stick-slip phenomenon is well taken into boundary conditions. Finally, determine that due to excessive friction in the presence of a large number of stabilizers indrilling. For finding the optimal position of stabilizers are so important and many parameters are important. In drilling those determine and correct applying axial force of the top wells to control the whirling and prevent unwanted transverse vibrations. Transverse vibrations cause damage to wells and drilling equipment is the most important factors.

Drill string, Non-linear vibrations, Weight on bit, Finite elements, Stick-Slip phenomenon