DOSKIL: A New Mechanism for Controlling Stick-Slip Oscillations in Oil Well Drillstrings

Carlos Canudas de Wit (1) , Francisco Rubio (2) , Miguel Corchero (2)

1 NECS - Networked Controlled Systems
2 ISA - Department of Automatic Control and Systems Engineering [Sevilla]

Limit cycles occurring in oil well drillstrings result from the interaction between the drill bit and the rock during drilling operations. In this paper we propose to use the weight on the bit ($\mathbf{WoB}$) force as an additional control variable to extinguish limit cycles when they occur. An approximate analysis based on the bias describing function and completed with some simulations, provides good evidence that the rotational dynamics of the oil well drillstring displays such a behavior. In particular, we propose an adaptation law for the $\mathbf{WoB}$ named D-OKILL mechanisms, which results from a variant of the \emph{oscillation killer} (OSKIL) mechanism studied in detail in \cite{Canudas:05b}. In opposition to the heuristic control structure proposed in \cite{Canudas:05}, we show that the new Weight on Bit ($W_{oB}$) control law results in a globally asymptotically stable closed loop-system. Simulations applying the D-OSKIL mechanism show that the stick-slip oscillations can be eliminated without requiring a re-design of the velocity rotary-table control.

Domaines: Automatique / Robotique

Carlos Canudas de Wit, Francisco Rubio, Miguel Corchero. DOSKIL: A New Mechanism for Controlling Stick-Slip Oscillations in Oil Well Drillstrings. IEEE Transactions on Control Systems Technology, 2008, 16 (6), pp.1177-1191. ⟨10.1109/TCST.2008.917873⟩. ⟨hal-00394990⟩