Annual Report

Marine Subsea Fleet
Offshore Intervention Vessels
Key features
Class:
Length:
Width:
Draft:
Deck Area: 1 470 m 2
Accommodation:
Deadweight:
Speed:
Crane capacity:
Module handling
tower;
140 t
Dynamic
Positioning: 3
Intervention depth: 2 500 m
+ DNV 1A1 R Ship-shaped Well Intervention
Unit SF LFL* COMF-V(3)C(3) HELDK
CRANE OPP-F E0 DYNPOS-AUTRO NAUT-
OSV(A) CLEAN DESIGN DK(+) HL(2.8)
MODU CODE Safety Certificate
120,2 m
25 m
7–5 m
100 persons
40 single & 30 double cabins
Roll reduction tanks
Diesel-electric propulsion
8 700 t
14,5 knots
2 Work Class ROV’s, 3 000 m
140 t
The two SX121 vessels Sarah and Karianne are designed as state of the
art Offshore Intervention vessels. Both have multiple usage functions and
are particularly well suited for subsea construction and well interventions.
Subsea well intervention, which is regarded as a very promising market,
entails improving oil recovery from wells that have been in production for
some time. The operation is typically performed by lowering specialized
tools through the moon pool of the vessel, into the well. These tools can
then perform production logging, re-perforation, lubrication etc., with the
objective of improving oil recovery. Traditionally, these operations have
been carried out by exploration semi-submersibles. However, with rig rates
being significantly higher than for vessels, subsea well intervention operations
can be performed faster and more economically from purpose built
vessels such as Sarah.
Both Sarah and Karianne, are practically identical. The vessels have the
characteristic new X-Bow shape, which enables better fuel efficiency,
more space for accommodation in the bow of the vessel and better motion
characteristics.
The vessels are dynamically positioned (DP3) and hence do not require
mooring lines when stationed over the object. The vessels are designed
with a central moon pool in the deck and with a 140 t heave compensated
tower above. They have also a 140 t heave compensated crane and both
the tower and crane are rated for 2 500 m water depth
The hulls of vessels are being built in the Ukraine, while completion and
commissioning is performed at Ulstein Group’s shipyard in West Norway.
Annual Report 2009 Marine Subsea 13