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Seaflex Aids Underwater FPSO Mooring Retrieval
Unique Seaflex, a Unique Maritime Group company which is an
integrated turnkey subsea and offshore solution providers, has
facilitated a complex underwater lift project carried out for
Lundin Tunisia BV in approximately 300m of water.
Lundin Tunisia BV is a 40% stakeholder in and operator of the
Oudna field 80km offshore Tunisia.
Abandoned by Shell in the mid-80s when relatively small
discoveries in relatively deep water were still considered
unviable due to lack of pipeline infrastructure, with the advent
of the FPSO came a new way to make such fields viable. Oudna was
accordingly de-mothballed a decade or so ago, and serviced until
recently by the FPSO Ikdam.
At end of the field's viable lifecycle, the problem arose of how
best to decommission the FPSO - and in particular how to take
care of the delicate operation of disconnecting several hundred
tons' worth of moorings without incident.
After a series of technical discussions between Lundin and Unique
Seaflex, it was determined that a combination of 41
different-sized parachute-style Air Lift Bags (ALBs) up to 50t in
size were needed to be installed on the moorings to reduce their
tension to a manageable level. The deck-mounted linear winch was
rated to 450t, but because the three mooring anchors were
extremely well embedded in the sandy seabed, the effective
tension on the chafe chain would have increased by an estimated
1.5 to 2 times the original 400t.
The use of Unique Seaflex ALBs allowed the deck-mounted linear
winch to pull on the chafe chain so as to slacken the connection
to the Ikdam deck hook. The connecting shaft was then pulled out
from the wren hook and by doing so, freed the chafe chain thus
allowing the mooring system to gently be lowered on a wire,
thereby de-tensioning the system.Once released, the chafe chain
was transferred to a nearby AHTV which held the de-tensioned
mooring system whilst the Ikdam FPSO disconnected.
Along with the fleet of ALBs, Unique Seaflex also supplied all
the heavy duty shackles and lifting slings as well as an air
inflation/deflation system and a topside technician to oversee
the operation and ensure the safest and most efficient use of the
package of equipment.
Commenting on this occasion, Graham Brading, Managing Director at
Unique Seaflexwho was instrumental in leading the Unique Seaflex
effort on this project proudly said, "Whilst we do supply
standard buoyancy products to solve standard buoyancy problems,
Unique Seaflex is always dedicated to bring out world-class
solutions when clients describe their operational challenges and
ask us to work with them to develop methods which will deliver
them the best possible technical, operational and commercial
outcome."
seaflex.co.uk
Jan 29, 2014
