2005 Annual Report - SBM Offshore

Report of the Board of Management
ideally suited to carry a large number of such deepwater
SCRs. SCR bending fatigue concerns in this use have been
addressed and shown not to be a problem in moderate to
rough environments.
Further internal R&D studies are underway to reduce the SCR
installation costs by placing the installation means on the
FPSO and use threaded couplings to join and install the
SCRs. As the SCRs are assembled, anchor handling type
tugs will be used to pull out the SCR to subsea wells or
manifolds where conventional tie-in procedures are used to
make the connection with subsea facilities.
Mid-water pipe systems
Product transfer between floating systems in deep and ultra
deep water is often more efficient if handled at minimal depth
by mid-water pipe systems. Two such systems having
distinct uses have been developed. The Trelline for large
diameter flexible lines used in the transfer of stabilised crude
from FPSOs to export buoys, and the Gravity Actuated Pipe
(GAP) for the transfer of multiple live produced fluids
between Dry Tree Units (DTUs) and an FPSO used for
processing of the hydrocarbon production.
The Trelline is a joint development between Trelleborg and
SBM for the qualification of a large diameter bonded hose
capable of much higher internal and external pressure and
tension than standard submarine loading hoses. This hose
received the API 17K certification by Bureau Veritas in 2003.
In 2004, work focused on the analytical modelling of the hose
carcass and the fatigue testing of the highly loaded first hose
section attached to the buoy. In 2005, completion of the final
certification work has made this hose a good alternative to
steel or unbonded flexible solutions. Hose advantages are
superior bending fatigue, large diameter availability and
installation without the use of expensive lay vessels. A first
order for the use of this technology was received in the course
of 2005 for an application in the Bonga field offshore Nigeria.
The GAP consists of a neutrally buoyant bundle of steel
pipes supported and tensioned at a near surface depth by
chains and weights attached to floating systems. The floating
systems transfer production fluids through the pipe bundle
and via vertical flexible lines at both extremities. This near
surface transfer greatly reduces flow assurance problems
caused by the formation of hydrates and waxing that would
occur with a bottom founded SCR piping system. The
38
GAP’s neutrally buoyant bundle also greatly reduces the
load placed on the floater when compared to SCR use, which
is quite important when designing TLP tie-ins. Studies of tieins
from two to thirty kilometres have shown the GAP to be
applicable in any deepwater production area of the world.
The first contract for the application of this technology was
received in 2005 for a tie-in of this type in the Kikeh field
offshore Malaysia.
TLP Depth Extension
TLP use generally has been thought to be limited to depths
up to 1,500 metres. This limit is a consequence of the TLP
mooring physics. The longer vertical mooring tendon
stiffness reduces with depth causing the TLP mass and
spring system to move to longer periods. These longer
periods are excited by commonly occurring short waves
causing fatigue in the tendons. Increasing tendon size to
reduce periods adds weight to the structure and cost to the
tendons thus making the TLP less competitive in deep water.
A passive air damping system that can be placed in the TLP
columns and which damps out the dynamics caused by
these longer tendons, has been developed. Work is
progressing to incorporate this air damping system in the
TLP. Once this system is integrated in the TLP, longer lighter
tendons will enable TLPs to be economically designed for
water depths up to 3,000 metres. Preliminary tests of this
system were successfully carried out in 2005 and early 2006
will see the final confirmation tests.
A gimbal joint accommodates angular motions between the FPSO piping
and the Trelline TM export hose