Abstract
Abstract In this article, we present a dynamic model for a generic drill-string. The model is developed with the intention for component-based simulation with coupling to external subsystems. The performance of the drill-string is vital in terms of efficient wellbore excavation for increased hydrocarbon extraction. Drill-string vibrations limit the performance of rotary drilling; the phenomenon is well known and still a subject of interest in academia and in industry. In this study, we have developed a nonlinear flexible drill-string model based on Lagrangian dynamics to simulate the performance during vibrations. The model incorporates dynamics governed by lateral bending, longitudinal motion, and torsional deformation. The elastic property of the string is modeled by the assumed mode method, representing the elastic deformation, with a finite set of modal coordinates. By developing a bond graph model from the equations of motion, we can ensure correct causality of the model toward interacting subsystems. The model is analyzed through extensive simulations in case studies, comparing the qualitative behavior of the model with state-of-the art models. The flexible drill-string model presented in this article can aid in developing system simulation case studies and parameter identification for offshore drilling operations.
Highlights
The drill-string is a vital component of a drilling rig multidomain system, and crucial in establishing the wellbore for hydrocarbon extraction
The drill collar section is a set of heavier pipes to produce enough weight on bit (WOB) when drilling and intervals of stabilizers keeping the string centred in the borehole
The torque on the bit is a consequence of the applied torque at the top, WOB, and the torque from the formation being excavated due to cuttings and the friction from the rock it self [1]
Summary
The drill-string is a vital component of a drilling rig multidomain system, and crucial in establishing the wellbore for hydrocarbon extraction. The model is used to analyze drill-string behavior in horizontal wells, and predicts the whirl phenomena close to the BHA together with the coupling effect for axial and torsional motion trough the bit-rock model. To the best of the authors’ knowledge, using the floating reference frame formulation for describing the coupling between lateral and torsional deformation and structuring this in a componentbased model for a drill-string, has not been previously presented. The flexibility of the pipe is represented by the elastic deformation p1e(z,t) and ψ(z,t) These vectors can be described utilizing mode shape functions obtained from solving the eigenvalue problem of lateral bending by means of the Euler-Bernoulli beam model, longitudinal vibration of a bar and torsional vibration of a shaft. This allows us to rewrite (12) in terms of the generalized coordinates as
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