MCE Deepwater Development 2015
Modularity of PLET and ILT design
for easy offshore installation and pipelay
March 24th 2015
Emmanuel Fontaine
1- PLET and ILT
functionalities
Agenda
2- Offshore installation
methods
3- Installation constraints
and impact on design
4- Mudmat modularity
5- Conclusions
2-Mar-15
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1 - PLET AND ILT FUNCTIONALITIES
• A PLET or ILT makes connection between the pipeline and a well or
manifold
• Contains special features:
- A piping bend with one connector or
more + valves and secondary featings
- A piping frame to hold the piping elements
and protect from dropped object
- A mudmat foundation to sustain:
 Gravity load
 Environmental loads
 Equipment loads
 Pipeline, Jumper loads
Mudmat can be sliding on seabed or allow the pipeline expansion (rails)
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2 - OFFSHORE INSTALLATION METHODS
FUNCTION
PLETILT
DESIGN
CLIENT
NEEDS
Installation Vessels
3 Types of structure
3 Installation
modes
PLET – First End
PLET - Second End
S-Reel-J lay
Inline Tee (ILT)
Thus 9 Groups of
design to cope with
vessels and
structure types
VESSEL
TO
INSTALL
• Requires to accomodate a range of installation methods
• Needs to cope with installation constraints
• Subsea Structure needs thus to be modular: Piping module; Mudmat
module; Special double joint module
• Some part are standardized with specific dimensions for flexibility and
variety in use (S-J-Reel)
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2 - OFFSHORE INSTALLATION METHODS
Double joint module
Piping module
Assembly
in S-lay
firing line
Stinger
PLET in
Catenary
(S-type)
Reel lay
work
station/
welding
station
PLET in
Catenary
(J-type)
S-LAY
Foundation module
Buoyancy module
Piping
module +
double joint
module +
foundation
PLET
handling
system
REEL
LAY
Buoyancy module
Piping
module +
double joint
module +
foundation
J-lay
tower/
welding
station
PLET
handling
system
Buoyancy module
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PLET in
Catenary
(J-Type)
J-LAY
2 - OFFSHORE INSTALLATION METHODS
REEL-LAY INSTALLATION SEQUENCE
• PLET installed in Reel-lay
• A PLET handling system (PHS) skids the structure aft and
transversally into the workstation for welding up to pipeline
Lay ramp
at vessel Stern
Aligner Wheel
Pipe
Storage drum
PLET Handling System
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Seven Oceans
PLET in the
workstation
2 - OFFSHORE INSTALLATION METHODS
REEL-LAY INSTALLATION SEQUENCE – Laydown case
PLET
Final landing of complete PLET
or simple piping module on a
Pre-installed foundation.
Foundation could also be postinstalled.
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2 - OFFSHORE INSTALLATION METHODS
J-LAY INSTALLATION SEQUENCE – Laydown case
• PLET installed in J-lay
• Pipeline and structure are deployed along vessel side with a J-lay tower
J-lay tower structure
J-lay tower
PLET
handling
frame
Seven Borealis
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PLET
Pipeline catenary
2 - OFFSHORE INSTALLATION METHODS
J-LAY INSTALLATION SEQUENCE - Laydown
PLET up-righted
Buoys
Pipeline catenary
Last stage: Final Landing of the all integrated PLET or single piping
module on a Pre-installed foundation. The foundation can also be postinstalled.
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2 - OFFSHORE INSTALLATION METHODS
S-LAY INSTALLATION SEQUENCE – ILT CASE
DOUBLE JOINT
MODULE
PIPING
MODULE
 For S-lay, the challenge is having the Piping
module pass along the firing line: may be
installed before/after tensioners
 Joints are welded, Field joint coated
 Tensioners are opened to their maximum range
allowing the double joint module to transit
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2 - OFFSHORE INSTALLATION METHODS S-LAY
S-LAY INSTALLATION SEQUENCE – ILT CASE
• Then the structure exits the
firing line and enter the
stinger
• Cross of the overbend region
• Buoyancy is connected
• Exit the stinger and last
rollers
• Last stage: Final Landing of
the complete ILT or single
piping module on Preinstalled foundation. Mudmat
can also be Post-installed.
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2 - OFFSHORE INSTALLATION METHODS
ALTERNATE DEPLOYMENT TABLE
• Use a deployment table (after
pipeline recovery after a Reel
J-S lay)
Abandonment cable
• Can be used for very
large/heavy structure
• Not applicable for ILT
• Requires recovery of the line
and installation of PLET in a
second stage
PLET
• Can be done with a second
vessel (without J/S or Reel
capacity)
Hang-off table
Pipeline catenary
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3 - INSTALLATION CONSTRAINTS AND IMPACT ON
DESIGN
• We have a wide range of installation constraints and Contractor
needs to integrate them in the PLET/ILT design.
• Need to specialize/adapt the design for each vessel tool.
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•Integrated to
piping module
for Reel and Jlay
•Separated for Slay
Foundation module
•Similar for all
3 modes S,
Reel, J
•But Requires
special
interfaces :
the PLET
handling tools
of Reel and Jlay towers
Pipeline special joint
Piping module
• For foundation the greatest flexibiltity is coming with the Pre and
Post-installed mudmat.
•Generally
integrated (Reel/J)
•Can be separated
for S-lay
•Can be Pre or Post
installed for all 3
modes
•Can be fixed to
piping module or
allow it to slide (
with rails)
3 - INSTALLATION CONSTRAINTS AND IMPACT ON
DESIGN
With interface for J-lay handling
With interface for Reel-lay handling
PLET/ILT
MODULE
TYPES
2-Mar-15
With separated piping
With special double joint
frame for S-lay handling
(S-lay firing line)
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3 - INSTALLATION CONSTRAINTS AND IMPACT ON
DESIGN
Mudmat integrated to PLET/ILT
Pre-installed mudmat
(w/o foldable wings)
PLET/ILT
FOUNDATION
MODULE TYPES
Suction Pile for stab and hinge over
system
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Post-installed mudmat
4 - MUDMAT MODULARITY
• The structure overall size is a constraint for the offshore
deployment.
• The mudmat can be quite large and heavy.
• The weight of the PLET is increased due to the mudmat (+ 1020 MT).
• Additional buoyancy is required for the mudmat.
• The mudmat is adding a hydrodynamic mass (limit sea states).
• The installation time is increased as well as risks to deploy
heavy and large structure.
• Solutions :
 Post-install the foundation on a pre-installed piping module
(patent pending)
 Pre-install the foundation and land the piping module inside
(patent pending)
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4 - MUDMAT MODULARITY
POST-INSTALLED MUDMAT SOLUTION
• Video of installation stages: the piping module exits the
stinger, goes in the sagbend transit and lands on seabed,
Mudmat is then connected by the top (patent pending)
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4- MUDMAT MODULARITY
PRE-INSTALLED MUDMAT SOLUTION
Piping module and frame
Mudmat module
Mudmat
Piping module
and frame
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4- MUDMAT MODULARITY
GAINS WITH A MODULAR MUDMAT APPROACH
Geotechnic
Post-installed:
Mudmat is connected
by the top
Final settlement of the
assembly is enabled
by load transfer of
piping module on the
mudmat
Pre-installed:
Mudmat is preinstalled on seabed
Mudmat settlement
occurs with selfweight
of foundation, and
further after piping
module landing
Both: No size limit to
cope with very soft
soil
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Pipeline
Both:
Can be used with
S/Reel/J lay modes
Residual plastic strain
(S & Reel lay) may
induce a pipeline axial
rotation
Buoys counter the
rotation and residual
torsion to remain
small for mudmat
connection (postinstalled case) or
piping module tilt
(pre-installed case)
Less buoyancy
required in catenary
Structure
Installation
Both:
There is no size
limitation for the
mudmat
Post-installed:
No need to oversize
the mudmat for
installation tolerances
The piping frame can
be sliding on mudmat
and accommodate
large thermal
expansion
Pre-installed:
Mudmat size needs to
account for installation
tolerances +/-5m
Installation is
reversible: recovery is
possible without
overstressing the
piping frame
Conception is
modular and can be
standardized
Both: installed
separately and can be
with a smaller vessel
Lighter and safer to
handle with vessel
cranes
5 - CONCLUSIONS
• S-Reel-J methods require specific interfaces on PLET/ILT
modules for installation.
• Design must take into account these constraints (in piping
and mudmat module) by having common part related to
installation method.
• Thinking modular ease the design and installation
• The Pre or Post-Installed mudmat modules offers great
flexibility for installation
• The Pre and Post-Installed mudmat design are applicable to
S, J or Reel-lay
• A separate foundation module allow lighter structure in the
firing line (the structure is easier to handle)
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• Thank you for your attention
• Any Questions ?
• Email
[email protected]
This presentation only reflects the opinion of its author and does not
imply endorsement by the company to which acknowledgements are
made.
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