Calibration of Dynamic Riser Analysis Using Measured Motion Data

 Abstract

For design and analysis of dynamic flexible riser motions, the common practice is to use tailor-made software to create an analysis model based on a large set of assumptions and simplifications regarding hydrodynamic loading and interaction between objects. Normally, most of the applied input values are based on theoretical considerations rather than tests and/or actual measured data, and it can be difficult to assess the overall level of conservatism.

When performing analyses on existing systems e.g., lifetime extensions, it is possible to reduce uncertainties by harvesting actual motion data and calibrate the analysis models to obtain a
sound level of conservatism.

In the case described in this paper, dynamic motions of both the Åsgard B semi-submersible platform and the Mid Water Arch (MWA) were measured throughout an entire winter season and used to calibrate the analysis model. The intention was to develop a method for improving accuracy in modelling of risers over the Åsgard B MWA structure in OrcaFlex

Authors

Karina Bruun Mortensen
Advisor at 4Subsea

Håvard Skjerve
Lead Engineer at 4Subsea