A rotor dynamics modal vibrational analysis of a water well rig drill string

Abstract

Drill String (DS) vibrations are excessive and cause early failure of various parts of the drill string due to fatigue. A drill string is a part of the rig bottom that consists of drill pipe, a drill collar, and a bit. The more the drill pipes are connected, the longer the drill string. The phenomenon caused by drill string vibrations can be avoided by stopping the drill string to rotate or move at its natural frequency, or, in other words, to avoid resonance. Rotational Speed (RS) in the drill string causes lateral vibrations and stick-slip in torsional vibrations. This research investigates vibration under the action of parameters such as water well drill string lengths and rotational speeds. A drill string was finite element modelled in the Analysis of Systems (ANSYS) workbench 2020, mechanical. The Campbell diagram was used to analyze critical speeds, Backward Whirl (BW), and Forward Whirl (FW) and drill string length.