Session: 04-01-02 Flexible Pipes and Umbilicals II

Paper Number: 104682

104682 - Calibration of Dynamic Riser Analysis Using Measured Motion Data 

When designing and analyzing dynamic flexible riser motions, the common practice is to use software specifically developed for this purpose. However, an analysis is based on several assumptions and simplifications regarding hydrodynamic motions and interactions between objects: when linking for instance an FPSO with a midwater arch (MWA) with flexible risers, the dynamic behavior is derived as a function of the combined impact from vessel RAOs, flexible riser properties, hydrodynamic forces, and MWA buoy data. As a base case, most of the applied input values are based on theoretical considerations rather than test and/or actual measured data, and the resulting motions can be inaccurate.

When performing analyses on existing systems, e.g., lifetime extensions, it is possible to reduce uncertainties by harvesting actual motion data and calibrate analysis models to obtain a sound, but not overly conservative, level of conservatism.

In the user case described in this paper, dynamic motions of both the Åsgard B platform and the MWAs are measured throughout an entire winter and used to calibrate the analysis model.

The intention was to identify vessel RAO conservatism (or the opposite) and, after eliminating potential RAO inaccuracies, develop a method for accurate modelling of MWA structures in OrcaFlex. 

Key words:  Mid water arch, Flexible risers, Sensors, Monitoring, Subsea structures, Calibration, Dynamic Software

 

Presenting Author: Karina Bruun Mortensen 4Subsea

Presenting Author Biography: Educated in Coastal engineering, marine structures, fluid dynamics, with MSc Certification from the Technical University of Denmark (graduated March 2007).

More than 15 years of experience, worked in Equinor as Principal Engineer, Platform Technology, Dynamic Risers with a position lead of flexibles team in subsea lines modifications. Have been working in flexible pipe manufacturers, in different roles related with pipe design and engineering team management.

Actually is SURF Advisor in 4Subsea Expert Services team.

Authors:

Karina Bruun Mortensen 4Subsea
Håvard Skjerve 4Subsea