DS0704 - Fondements du numérique

Modeling And Control of Self-excited vibrations for DRILLing – MACS-DRILL

Submission summary

The proposed project is a collaborative research between two important and recognized French laboratories, GIPSA-lab and CAS-ARMINES, with the industrial cooperation of Kelda Drilling Controls. It will investigate modeling and control of drilling systems.

Drilling processes represent a substantial share of production costs for production of numerous natural resources or geothermal energy. This project focuses on mechanical vibrations related to the drilling process. Suppressing such oscillations requires the investigation of fundamental problems in control of time-varying delay systems, that we propose to conduct.

The drilling process consists in the creation of a borehole (the well), generally several thousand meter long. To do so, a long flexible drillstring is set into a rotating motion around its main axis. At the end of the drillstring, the “drill bit” cuts, shatters and crushes the rock. The irregularity of the bit-rock interaction causes the occurrence of mechanical vibrations that damage the facilities and are the culprit of important costs.

Traditionally, mechanical vibrations are divided into axial, lateral and torsional, and separately studied. An important share of the literature focuses on torsional oscillations. These are generally considered as a consequence of dry friction forces, modeled as decreasing functions of the rotating velocity. Torsional vibrations are then interpreted as an occurrence of the well-known stick-slip phenomenon. This interpretation gave rise to numerous contributions in the control literature, as well as commercial software suppressing torsional vibrations. Experience reports suggest that their performances are poor at low rotational velocities and for drillstring longer than 2500 meters.

Laboratory experiments recently reinterpreted suggest, however, that friction forces are independent of the rotational velocities in the drilling process. These make the aforementioned interpretation irrelevant. Rather, to accurately model the dynamics of drill bits, the experiments indicate that cutting forces need to be taken into account. These forces couple the axial and torsional dynamics and induce a delay depending on the position of the drill bit itself. Interestingly, a consequence of this new formulation is that the torque applied to the drill bit does depend on the rotational velocity, but as a consequence of the dynamics rather than a structural property of the forces applied to it.

This new paradigm calls for a reformulation of control problems associated with mechanical vibrations. One must now design control laws for state-dependent delay systems. Furthermore, it is important to take into account the propagation of the oscillations along the drillstring between the surface actuators and sensors and the source of the instability located at the bottom hole, in order for the controller performance not to depend on the length of the system.

The goal of this project is, therefore, the design of controllers for state-dependent delay systems with input and measurement delays, and their application to mechanical vibrations.

The project is classically divided in three Working Packages: modelling, control, experimental validation.

Project coordination

Delphine Bresch-Pietri (Grenoble Images Parole Signal Automatique - UMR 5216)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

Kelda Kelda Drilling Controls
GIPSA-Lab Grenoble Images Parole Signal Automatique - UMR 5216
ARMINES (CAS) ARMINES Centre Automatique et Systèmes de Mines ParisTech

Help of the ANR 309,970 euros
Beginning and duration of the scientific project: September 2015 - 42 Months

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