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TRICERATOPS The Case for a New Deepwater Concept

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1 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? (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

2 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

3 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

4 10ft Triceratops ? 10,000ft Water Depth Ranges for PLATFORM Concepts
Dry Trees Caissons Wet Trees Posted Barge Jackets FPSO Tower Semi FPS TLP Mini-TLP BLS Triceratops BLS Spar Spar ? 10,000ft

5 Heavier & ‘Stretchier’
Tendons & Buoyant Legs TLP 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. Tendons become Heavier & ‘Stretchier’ with increasing WD => RESONANCE

6 Reducing Ultra-deep TLP Costs
$$$ If a ‘buoyant tendon’ is extended through the surface, we might call it a ‘tethered buoyant tower’ Tendons are costly in deep waters, but rigid TLP ‘nodes’ are costly at ALL water depths

7 Self-standing (buoyancy supported) Risers
Multi-Function Barge Spar Tree The ‘self-standing risers’ used in spar are simple ‘Tethered Buoyant Platforms’ With Trees as their payloads

8 When is a Spar NOT a Spar? Spar When it’s Tethered and becomes a
Tree Trees When it’s Tethered and becomes a Buoyant Leg Structure Well & Riser

9 Triceratops - a tethered buoyant platform structure
Three (or more) tethered buoyant towers acting together can support “a lot”! Triceratops - a tethered buoyant platform structure Buoyant Columns Tension Legs (partially flooded) Hybrid Gravity/Suction Anchors

10 Triceratops – a tethered buoyant tower structure
Workover/Completion Rig Float-over Truss Frame Deck w/ Modules Contact “Hinge” Nodes CVAR Tubing Tieback Riser Buoyant Columns Tensioned Restraining Legs (may be stepped in wall thickness, tapered in section, or partially flooded) Hybrid Gravity/Suction Anchors The columns are installed and stand independently until the deck ties them together

11 Triceratops – a tethered buoyant tower structure
Workover/Completion Rig Contact “Hinge” Nodes 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 Buoyant Columns Tension Legs (partially flooded) Hybrid Gravity/Suction Anchors

12 Triceratops – a Compliant Concept that is readily adapted to a wide range of water depths
Ultra-deep Water Moderate Depths Deep

13 Why Triceratops? Payload & deck area virtually unlimited
Workover/Completion Rig Why Triceratops? Float-over Truss Frame Deck w/ Modules Contact “Hinge” Nodes 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 Buoyant Columns Tension Legs (partially flooded) Hybrid Gravity/Suction Anchors

14 Basic Comparisons TLP Spar BLS/TBT T’tops WD range 500-5,000ft
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)

15 Risks v. Benefits Cost Risks Project Schedule 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

16 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 Fabrication Topsides + Hull/mooring $66MM +$121+28MM. $85MM +$51MM Installation & HUC $27MM $11MM Total Cost, excl. Risers/well systems $289MM $179MM delta = -$110MM Work-over + Completion Rig is leased =>Savings >30%

17 Triceratops Introductory Study Ultra-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

18 “A Triceratops horridus gallops”, a painting by Douglas Holgate
TriceraTOPS’em All!! “A Triceratops horridus gallops”, a painting by Douglas Holgate

19 “Triceratops horridus charges through the forest”
By, Frank DeNota

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