Avoiding harmful oscillations in a drillstring through dynamical analysis

Abstract

Complexity of oilwell drillstrings makes unfeasible the direct application of control methodologies to suppress nondesired oscillations existing in these systems. A reasonable alternative is to develop operation recommendations and parameter selection methods to guide the driller to avoid such oscillations. In this paper, by using dynamical analysis tools, operation recommendations and the detection of safe drilling parameters in a conventional oilwell drillstring are presented. To this end, a more generic lumped-parameter model than those considered until now is proposed. Particularly, this model takes into account the fact that the drillstring length increases as drilling operation makes progress. The analysis of a sliding motion giving rise to self-excited bit stick-slip oscillations and bit sticking phenomena at the bottom-hole assembly is performed. Finally, the identification of key drilling parameters ranges for which non-desired torsional oscillations are present is carried out by studying Hopf bifurcations in the vicinity of the system equilibrium point when rotary velocities are greater than zero.

Suppressing stick‐slip oscillations in underactuated multibody drill‐strings with parametric uncertainties using sliding‐mode control

“…The literature using the lumped-parameter model for control purpose is vast, e.g. [4,5,6,7,8]. Navarro-López and Cortés [4] used a generic lumped-parameter model to analyze self-excited stick-slip oscillations at the drill bit by identifying the ranges of key drilling parameters for which non-desired torsional oscillations can be avoided.…”

“…[4,5,6,7,8]. Navarro-López and Cortés [4] used a generic lumped-parameter model to analyze self-excited stick-slip oscillations at the drill bit by identifying the ranges of key drilling parameters for which non-desired torsional oscillations can be avoided. In [5], Navarro-López and Licéaga-Castro proposed a dynamical sliding-mode controller to avoid different bit sticking problems appearing in the model.…”

Numerical and experimental studies of stick–slip oscillations in drill-strings

“…In the present work, we will consider the lumped-parameter model shown in Fig. 2, which has been studied in the past by various authors; see, e.g., [10][11][12][13]. The generalized lumped-parameter model can be written in a single-input and multi-output form as follows Fig.…”

“…2, we present a preliminary numerical study of a low-dimensional version of the lumped-parameter model (1). The dynamics of models of this type has been analyzed in the past (see, e.g., [22][23][24]); however, the numerical investigations of the stick-slip oscillations were carried out using direct numerical integration. In the present work, we will employ pathfollowing (continuation) techniques for non-smooth systems, which will allow us to gain a much deeper insight into the possible control strategies that can be employed to avoid stick-slip oscillations.…”

Dynamic stability of a stepped drillstring conveying drilling fluid

“…Working under complex conditions, the drillstring is apt to lose stability and collides with the borehole wall seriously. It would lead to reduction in both the quality of wellbore and the service life of drilling tools, and result in the raise of drilling costs ultimately (Hakimi and Moradi, 2010;Zamani et al, 2016;Navarro-López et al, 2007).…”