TRICERATOPS The Case for a New Deepwater Concept Is there room for a new concept? Principles and limitations of (TLP’s) What’s at the core of spar concepts?

TRICERATOPSThe Case for a New Deepwater Concept

• Is there room for a new concept?

• Principles and limitations of (TLP’s)

• What’s at the core of spar concepts? (risers)

• When is a spar not a spar?

• Reducing deepwater TLP costs

• A Buoyant Leg Structure is an optimized tethered buoyant tower

• Clustering Towers to support big payloads

• Triceratops (assembly)• Triceratops in

shallower waters

Is there room for a new concept?

• Currently there are only 3 proven concepts for deepwater dry-tree platforms– Towers (steel - Bullwinkle, Lena; concrete - Troll, Draugen)

– TLPs (& mini-TLPs)– Spars

• Only TLPs and Spars have been proven for very deepwaters and large payloads

• Large payload deepwater TLPs have very expensive hulls & mooring systems

• Spars have very expensive hulls and riser systems• TLPs have great motion characteristics, but costs

& dynamic response increase dramatically in ultra-deep waters

Enter BLS & Triceratops

• Buoyant Leg Structures are tethered spars (i.e., vertically restrained)

• The BLS combines the qualities of spars and TLPs where its deep draft hull limits vertical excitation

• The BLS can give better motions and more convenient riser systems/well access than spars with much smaller, simpler hulls than spars or TLPs

• A Triceratops combines 3(or more) tethered spars to support very large production facility deck structures

• Either one may support dry tree or subsea well risers

• AND….BLS & Triceratops will be cheaper than TLPs & spars for competing payloads

Wet TreesDry TreesCaissons

Posted BargeJackets

Tower

TLP

Spar

FPSO

Semi FPS

Spar

Water Depth Ranges for PLATFORM Concepts

BLS

Mini-TLP

BLS

Tendons & Buoyant LegsTLP

Tendons becomeHeavier & ‘Stretchier’

with increasing WD=> RESONANCE

Tendons’ useful strength may be preserved by stepping wall thickness & partial buoyancy, but large steel cross-

sections are still required to avoid vertical mode RESONANCE.

Reducing Ultra-deep TLP CostsTLP

Tendons are costly in deep waters, but rigid

TLP ‘nodes’ are costly at ALL water depths

If a ‘buoyant tendon’ is extended through the

surface, we might call it a ‘tethered buoyant tower’

Self-standing (buoyancy supported) RisersSpar

Multi-FunctionBargeTree Tree

The ‘self-standing risers’ used in spar

are simple‘Tethered Buoyant

Platforms’With Trees as their

payloads

When is a Spar NOT a Spar?Spar

Tree

When it’sTethered

and becomes aBuoyant

LegStructure

Trees

Well & Riser

Triceratops - a tethered buoyant platform structure

Buoyant Columns

Tension Legs (partially flooded)

Hybrid Gravity/SuctionAnchors

Three (or more) tethered buoyant towers acting

together can support “a lot”!

Buoyant Columns

Tensioned Restraining Legs (may be stepped in wall thickness,

tapered in section, or partially flooded)


Float-over Truss FrameDeck w/ Modules

Contact “Hinge” Nodes

Workover/CompletionRig

CVAR Tubing TiebackRiser

Triceratops – a tethered buoyant tower

structure

The columns are installed and

stand independently

until the deck ties them together

Buoyant Columns



CONCEPT FEATURES/CHALLENGES-

•Float-over Truss Frame Deck w/ Modules•Typical top-tensioned or Compliant Vertical Access Dry Tree Tieback risers can be used•Deck stays horizontal as platform offsets in wind, waves & currents (like a TLP)•Contact nodes between deck structure and buoyant columns allow angular deflections (acting as a bi-directional “hinge” joint)•Hinge points can face upward (to deck) or downward (to columns)•Hinges require careful design but loads and angles are well within limits for existing flex-joint designs•Columns are only about 450ft in draft (versus 700+ft for spars) and are relatively small diameter•Heave restraining leg allows column draft to be limited and still maintain great motions•Column vertical weight (mass) distribution optimized for stability and limited excitation to restraining legs•Restraining legs experience very little vertical resonant excitation due to column design/draft



Triceratops – a tethered buoyant tower structure

Ultra-deepWater

ModerateWaterDepths

DeepWater

Triceratops – a Compliant Concept that is readily adapted to

a wide range of water depths

Buoyant Columns



Float-over Truss FrameDeck w/ Modules



Why Triceratops?

• Payload & deck area virtually unlimited• Tethering costs minimized

•Tethering loads minimized as with TBT/BLS• Concern about vertical mode resonance limited

• Deck sees TLP-like motions• Lower cost deck fab/install• Small diameter columns cheaper to fabricate

• Can be fab’d in GoM without long tow

• Wells can be located beneath deck or well away from foundations

Basic Comparisons

TLP Spar BLS/TBT T’tops

WD range 500-5,000ft

1,500-10,000ft

1,000-8,000ft

500-8,000ft

Payload capacity

1,000-60,000t

1,000-30,000t

1,000-20,000t

5,000-60,000t

Motions Vertical modes restrained; heave-pitch/roll cross-coupled

All vertical modes minimized by design; surge/sway limited by size

Heave restrained, roll/pitch minimized by design principles

Heave restrained, roll/pitch & surge constrained by configuration

High Cost elements

Nodes at column tops & bottoms, tendons, installation

Massive hull; spread mooring, deck installation,

Restraining-leg (cheaper than tendons); deck installation

Restraining-legs (cheaper than tendons)

Risk Installation; Well hazards affect foundations

Deck install & pitch/riser fatigue in well-bay

Pitch angle at tension-leg

New Ideas

(see next slide)

Risks v. Benefits• Cost Risks

– Replaces complex rigid nodes at deck & pontoons on TLPs with compliant compression bearing joints at deck

– Reduces tethering steel/cost to minimum required for station-keeping

– Avoids complex tendon porches

– Avoids massive spar hull

– Avoids complex riser systems & buoyancy on spar risers

– Allows simple deck installation

• Project Schedule Risks– Small, simple hull & tether structures

easily fab’d locally (e.g., in US)– Towing column/tether as one unit with

up-ending at field limits critical exposure periods for installation

– Hook-up & pre-commissioning inshore can be maximized

• Design/Safety Risks– Simple structures compared to TLP

– Tethers see low dynamic loads

– Wells can be located remote from foundations/anchors

– Hulls float stably with restraining leg removed

– Provides large deck area for safe distribution of hazardous area

• Operational Risks– Limited inspection challenges

– Easy maintenance of readily replaced components

• Reservoir Risks– With tethers (ie., restraining leg)

removed entire platform can be towed to new field as one unit or deck can be easily removed for upgrade inshore

and re-installed at new field

Apparent Cost Advantages

Spar T’tops

Mission 6000ft WD, 100mbopd, 12 prod. risers

Payload, Incl. Deck structures

14,740t 16,130t

Column Dia. & Draft, Displacement

132ft x 700ft 40ft x 400ft

49,900t

Engineering & Project Mgt

$47MM $32MM

FabricationTopsides + Hull/mooring

$66MM

+$121+28MM.

$85MM

+$51MM

Installation & HUC $27MM $11MM

Total Cost,excl. Risers/well systems

$289MM $179MMdelta = -$110MM

Work-over +CompletionRig is leased

=>Savings >30%

Triceratops Introductory StudyUltra-deepwater Applications

• Location & WD• Mission/Payload Characteristics• Definition of System Components• Performance Criteria & Safety Considerations

– Global Analysis– Contact “Hinge/Node” loads and behavior

• Installation Planning and Estimates• Costs• Schedule

TriceraTOPS’em All!!

“A Triceratops horridus gallops”, a painting by Douglas Holgate

http://dinosauricon.com/artists/index.html

By,FrankDeNota

“Triceratops horridus charges through the forest”

Documents

TRICERATOPS The Case for a New Deepwater Concept Is there room for a new concept? Principles and limitations of (TLP’s) What’s at the core of spar concepts?