Managing oil drilling efficiency in bend drill pipes-an under actuated system perspective

Lateral vibrations are known to be the most destructive type of vibrations affecting rotary drilling. A whirling drill bit is one of the most prominent outcomes of lateral vibrations. Hence, it is imperative to research methodologies to minimize the drill bit whirl in order to maximize rotary drilling efficiency. Drill bit whirl can be either due to a bend drill string or due to the effect of an unbalanced drill bit. Both the cases lead to an in homogenous borehole which leads to increase in severity of the vibrations. This paper presents an analysis of the controllability of the drill bit whirl in bend drill pipes. Experimental tests conducted are analyzed and presented. The bit whirl due to drill bit bend is discussed as a probable special case of an under actuated system. A few typical under actuated system control issues are presented and the applicability of controllability solutions to the bend drill string whirl problem is discussed.