1. Introduction

The presence of drillstring vibrations is the main cause of performance loss in the perforation process for oil and gas. It provokes premature wear and tear of drilling equipment resulting in fatigue and induced failures such as pipe wash-out and twist-off. It also causes a significant wastage of drilling energy and may induce wellbore instabilities reducing the directional control and its overall shape. In the oil industry, the improvement of the drilling performance is a matter of crucial economic interest. This introductory chapter gives an overview of the three main types of vibrations occurring during drilling operations: torsional (stick-slip), axial (bit-bounce) and lateral (whirling). It also presents the basics of a vertical drilling operation and a description of the system components. The scope and organization of the monograph is provided.