Thunder Horse PLET Reconnect

DOF Subsea Survey & Positioning
Case Studies - Thunder Horse PLET
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Thunder Horse PLET Reconnect
Part 1
Client
Heerema/BP
Field & Location
Gulf of Mexico
Project Type/Discipline
Marine Construction & Support
Water Depth
1844m
Date Award
December 2006
Date Completed
January2008
The Thunder Horse production facility consists of a
semi-submersible floating production system utilising
a semi-taut moored Production Drilling and Quarters
Vessel (PDQ). The minimum and maximum water depths
for Thunder Horse are approximately 5,520 ft (1,682 m)
and 6,270 ft (1,911m) respectively.
Scope of Work
During 2004-2005, Heerema Marine Contractors Nederland BV (HMC)
performed the installation of several PLETs, Suction Piles and Flowlines for
BP. Subsequent to the completion of the installation, defects were discovered
in some of the subsea structures. The remedial action involved recovery of
the manifolds, jumpers and PLETs.
HMC was contracted to perform the re-installation of the twenty one PLETs, two
manifolds and the associated temporary holdback and permanent piles. For the
four PLETs located under the PDQ, keel haul operations were employed using
the DCV Balder, the MV Normand Master and the SV Union Manta to recover
the flowlines from the seabed, weld on the new PLETs and install them back
onto the seabed. This keel haul operation is where C3D and C4D were utilised
as effective visualisation tools during planning and execution.
© DOF Subsea 2016. Information correct at time of going to press.
www.dofsubsea.com
DOF Subsea Survey & Positioning
Case Studies - Thunder Horse PLET
ROVs were positioned to monitor the rigging and the clearances
between risers using Sonar
A field layout drawing was posioned on the
seabed to act a target box for the PLETs
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PLETs were lowered between SCRs with very little clearance at each side
Project Execution
The project comprised a complex keel-haul procedure, utilising multiple vessels
to recover four flowlines, weld on the PLETs and then install the PLETs down
onto the seabed. Due to multiple SCRs (Steel Catenary Risers) installed into
the Thunderhorse PDQ semi-submersible, the flowlines and PLETs had to
be threaded through these SCR’s during recovery and re-installation
without damaging any of the existing lines. The clearance between risers
was limited (15ft), leading to a high risk of conflict. This is where the benefits
of C3D assisted the project team.
Benefits of 3D Visualisation
Models of PLET and rigging were included
in the catenary models to add detail and
realism
Complex deep water projects test our ability to develop and perform intricate
engineering procedures safely, efficiently and without damage to equipment.
During this project, C3D provided the ability to create geospatially accurate
environments during procedure development, and to simulate each step of
the offshore installation using engineering analysis software. This allowed the
risks to be evaluated effectively so procedures could be optimised to reduce
these risks, and in turn costs.
C3D accurately visualised all procedures prior to live offshore operations, with
respect to clashing and clearance analysis, ROV accessibility, hazard identification
and training and familiarisation. This helped to drastically reduce the costs
of project planning and risk mitigation.
© DOF Subsea 2016. Information correct at time of going to press.
www.dofsubsea.com