New formulation and application of the segment method for extensible risers

ABSTRACT

Slender systems in which the length dominates over the other dimensions are an integral part of offshore systems. Modelling of such systems takes into account bending, sometimes torsional, and more rarely longitudinal deformations. The paper presents a new formulation of the segment method, in which the elongation of a slender link is considered; it is also possible to restrict analysis to one selected deformation while neglecting the others, which results in a very high computational efficiency. The models take into account the impact of the environment and the flows inside risers. Validation is carried out by comparing the simulation results with those presented by other researchers. The method is then applied in the solution of dynamic optimisation problems concerning the re-entry process, which includes disconnecting the riser from the wellhead and moving the platform with the riser. Due to consideration of sea currents, this task is a spatial problem.

KEYWORDS:

• Segment method
• bending
• torsion and elongation
• dynamics of risers
• hydrodynamic forces
• dynamic optimisation

Disclosure statement

No potential conflict of interest was reported by the author(s).