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PhD thesis unlocks potential for offshore risers

Airindy Ayu Felisita (33) recently defended her PhD thesis in offshore technology. Her research could prove useful for the offshore industry’s use of so-called steel lazy wave risers.

The steel lazy wave riser (SLWR) was first installed in 2008 at Brazil’s BC-10 field. Since then, it quickly became a popular and competitive riser solution for application in deepwater locations. This is due to the riser’s satisfying performance when exposed to dynamic loadings and the relatively simple configuration (particularly when compared to hybrid risers).

However, as it was put to use only quite recently, this riser concept is still lacking in technology qualification and design validation, in addition to very little field experience and data. Felisita’s thesis presents a study on the application of SLWR in harsh environments combined with high-motions vessels.

Strength and fatigue

The main objective is to demonstrate and document various design aspects for application of SLWR in such situation. Main analysis aspects include strength and fatigue of the riser, specific challenges from the environments (internal solitary waves) and installation operation for the riser.

In addition, a potentially novel concept using SLWR for application in areas prone to glacial ice is also included.

These findings can be applied to the design of SLWR, particularly for understanding the riser’s dynamic performance in correlation with its geometric shape, the influence from soil characteristics and VIV.

Added safety

The potentially novel sidestep concept, using SLWR for application in areas with glacial ice, is very useful as it provides an additional safety barrier prior to turret disconnection.

The design method against internal solitary wave can be used as a verification method during early stages of riser design/field development planning.

The results from installation analysis can be used to identify possible installation methods, vessels and required weather window for installing SLWR in harsh environments.

Thesis and defence

Airindy Felisita’s thesis is titled «On The Application of Steel Lazy Wave Riser for Deepwater Locations with Harsh Environment». The research was supported by DEA E&P Norge AS.

Felisita's main supervisor was professor Ove Tobias Gudmestad at UiS. Felisita defended her thesis at the Faculty of Science and Technology on 19 January 2017.

Foto av Airindy Ayu Felisita

Airindy Ayu Felisita