Integrated Design Developmentof a

Low MotionSemisubmersible Hull Form

Contents

• The Semisubmersible as a Deep water Concept

• Hull Form Development and Optimization

• Hull Motion and Structural Verification

• Platform Features

– Hull

– Topsides

– Mooring and Riser System

• Conclusions

The Semisubmersible as a Deep waterConcept

• System components adaptable to ultra-deep water

• Concept supports wide range of topside payloads

• Track record of proven design and fabrication and methods

• Proven offshore installation methods with minimal risk

• Quayside Hook-up and Commissioning

Advantages

Limitations

• Currently, the concept is limited to applications with subseawells

Hull Form Development

CONSTRUCTION

TRANSPORTATION

INSTALLATION

OPERATION

-

FunctionalRequirements

PracticalAspects

Hull FormOptimization

DesignVerification

TOPSIDES

DRILLING

PAYLOAD

RISERS

HULL

-

OPTIMIZEDMOTIONS ANDSTEEL WEIGHT

-

ANALYSIS

MODEL TESTING

-

Work Flow Path

Functional Requirements

Basis Range of Application

Location Gulf of Mexico Adaptable to other regions

Water Depth 1830 m > 3000 m

Topsides 100 KBOPD150 MMSCFDDrilling26,000 Tonnes

Can be re-configured for largertopsides (>40,000 Tonnes)

Riser System Steel Catenary Risers:6 Production2 Test2 Water Injection2 Export18-inch Maximum Dia.4,500 Tonnes vertical load

Flexibility to accommodate additionalrisers and/or larger diameter

Basic Requirements

Practical Considerations

Draft LimitationOperating Draft (Max.) = 27.5m

• Structural efficiency• Stability / tow-out draft• Deck Installation

Column ConfigurationFour-column and Six-Column configurations studied

Six-column solution selected:• Structural benefit from reduced deck span• Improved rectangular deck layout (safety, piping, etc.)• Increased flexibility for deck construction

Ring Pontoon

Omni Directional Motion Response

• Transit Draft (Min.) = 12m• Flexibility for Deck Integration• Access to yards

Hull Form Optimization

Variables

Draft

Columns (number, size,spacing, shape,inclination)

Pontoon (length, aspectratio, bilge radius, shape)

Cross bracing / ringpontoon configuration

Constraints

Target motion RAOs

Heave natural period

Motion/Acceleration at RiserAttachment

Minimum GM

Deck area requirement

Minimum trimming ballast

Pontoon span / depth ratio

Maximum Draft

Transit draft

SOLVER

HULLWEIGHTMODEL

MOTIONRESPONSE

MODEL

Cycle II I-O perat ing

0 .0 0 0

0 .0 0 1

0 .0 0 2

0 .0 0 3

0 .0 0 4

0 .0 0 5

0 .0 0 6

0 .0 0 7

0 .0 0 8

0 .0 0 9

0 .0 1 0

0 5 1 0 15 2 0 25 3 0 3 5 40

Pe ri od (s e c)

An

gu

la

rM

ot

io

n(

ra

d/

m)

Pitc h , Hd g = 0

Ro ll, Hd g= 9 0

Cycle II I- Operat ing

0 .0

0 .2

0 .4

0 .6

0 .8

1 .0

1 .2

1 .4

1 .6

1 .8

2 .0

0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 0

Pe ri od(s e c )

He

av

e(

m/

m)

CG, Hdg = 0

CG, Hdg = 9 0

Pontoon We ight Coe ffic ients

P o ntoo n A spe ct R at io

Vol

ume

tric

Wei

ght

Coef

f.(t

/m3

)

D raf t = 2 2. 5 m

D raf t = 2 7. 5 m

D raf t = 3 2. 5 m

OPTIMIZED HULL

Hull Form Optimization

Morison Element formulation for heave pitchand roll motion

Added mass and inertia (wave) forcescalculated assuming hull as an assembly ofslender Morison elements

Closed-form equations for pre-integratedforces along longitudinal, transverse andvertical slender members

Motions are de-coupled by calculatingangular motions about an estimated center ofrotation

Special treatment (added mass corrections)at connections between elements andelement ends to obtain reasonablecorrelation with results from 3-D radiation /diffraction analysis

h_ toc

H_t ape r * (d raf t_r - Hp) d ra ft_r

Hp

Wpo

Xpon _Ytra ns * Yi

Yi

Xsp +Dco

Db _Dt * Dco Db_Dt *Dc i

Can t

r ad _col * Dco

r ad _col * Dci

Xsp

Xsp/3 Xs p/3

Ysp/2

Wpi

Dco

Wpx

p on_ Xtran s * XspDci

Motion Response Model

Example of Hull Idealization

Pontoon Weight Coefficients

Pontoon Aspect Ratio

Vo

lum

etr

icW

eig

ht

Co

eff

.(t

/m3

)

Draft = 22.5 m

Draft = 27.5 m

Draft = 32.5 m

Hull Form Optimization

Pontoon Aspect Ratio

a/b = 2 a/b = 3

Vo

lum

etr

icW

eig

ht

Co

eff

icie

nt

Increasing Draft

Steel Weights defined on a volumetricbasis

Correlated to actual and preliminarydesigns

Adjustments for draft / column (tankvent) height

Adjustments for pontoon height andaspect ratio

Steel Weight Calculation:

Hull Motion And Structural Verification

• Motion Response Prediction

• Comparison to Production Semi’s and MODU’s

• Model Testing

• Structural Verification

Hull Form - Key Features

• Six-columns

• Ring Pontoon

• Pontoon Shaped to ReduceMotion and Provide Omni-directional Response

• Enlarged Center Column andPontoon Section

• Pontoon Aspect Ratio MaximizesAdded Mass Contribution

• Pontoons Consist Entirely of FlatPlate Construction

• Columns Rounded to ReduceWave Run-up

Motion Characteristics

Heave Rao Pitch / Roll Rao

0.0000

0.0010

0.0020

0.0030

0.0040

0.0050

0.0060

0.0070

0.0080

0.0090

0.0100

0 5 10 15 20 25 30

Period (seconds)

Ro

ll/P

itc

hA

mp

litu

de

(rad

/m

)

Roll (Beam S eas)

Pitc h (Head Seas)

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

0 5 10 15 20 25 30

Period (seconds)

He

ave

Am

plitu

de

(m/m

)

0 deg (Head)

45 deg (Quartering)

90 deg (Beam)

Motion Performance Comparison

HEAVE MOTION @ CG, Hdg=90 (Beam Seas)

0.00

0.10

0.20

0.30

0.40

0.50

0.60

5 6 7 8 9 10 11 12 13

Tz (sec)

Sig

.Heave

/H

s(m

/m)

KBR Drilling and Production Semi

Production Semi 2

5th Generation Drilling Semi

Production Semi 1

Heave Rao Heave Response

100-YRHURRICANE

Heave RAO, Hdg = 90 (Beam Seas)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 5 10 15 20 25 30

Period (sec)

Heave

(m/m

)

KBR Drilling and Production Semi

Production Sem 2

Typical 5th Generation Drilling Semi

Production Semi 1

Motion Performance Comparison

Roll Rao Pitch Rao

Pitch R AO, Hdg = 0 (Head Seas)

0.000

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0.010

0 5 10 15 20 25 30

Period (sec)

Pit

ch

(ra

d/m

)

K BR Drilling and P roduct ion Sem i

Typic al Pro duction S emi

5 th Generation Drilling Sem i

Roll RAO, H dg = 90 (B eam Seas)

0.000

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0.010

0 5 10 15 20 25 30

Period (sec)

Ro

ll(r

ad

/m)

K BR Drilling and Product ion Semi

Typical Product ion Semi

5 th Generat ion Drilling S emi

Motion Performance Comparison

Heav e Acc eleration at Ris er P orch #2 , Hdg=45

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

5 7 9 11 13

Tz (se c)

Sig

.He

av

e.A

cc

'n/H

s[

(m/s

^2

)/m

]

Production Sem i #1

Production Sem i #2

KBR Drilling and Produ ction Semi

Vertical Acceleration At Riser Porch Locations

H eav e Acce leration at Riser Porch #1, Hdg= 45

0 .00

0 .02

0 .04

0 .06

0 .08

0 .10

0 .12

0 .14

5 7 9 11 13

Tz (sec)

Sig

.He

av

e.A

cc

'n/

Hs

[(m

/s^

2)/

m]

Product ion Semi #1

Product ion Semi #2

KBR Drilling and Production S emi

Model Test Verification

Heave Rao Correlation

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0 5 10 15 20 25 30

Period (sec)

He

av

eA

mp

litu

de

(m/m

)

DIFFRACTION ANALYSIS

Model Test (soft mooring)

Model Test (full mooring)

Structural Design Process

Hull Framing and Scantling Calculations

Global Hull FE Model (Patran):

•Shell & Bulkhead Plating

•Pontoon & Column Web Frames

•Column Deck Flat Plating & Girders

•Shell and Bulkhead Stiffeners (“Lumped”)

•“Dummy” Members for Risers Porches, Fairleads,etc.

Static and Mooring/Riser Loads (Patran):

•Hull Dead Weight and Operational Loads, including Ballast

•Topsides Dead Weight and Operational Loads

•Mooring Line & Riser Tensions

Global Topsides Model (Patran):•Primary Transv erse Trusses

•Primary Longitudinal Trusses

•Primary Deck Girders and Plating

Hydrodynamic Analysis (WADAM)

•Various Wav e Headings & Periods•Map Wav e Pressures and InertialLoadsonto Global FE Model

Determine Design Waves

•“Squeeze-Pry” Load between the Pontoons

•Global Torsional Moment

•Longitudinal Shear Force between Pontoons

Global Strength Analysis (SESAM)

•Stillwater + Hydrodynamic Loads

•Yield Checks

•Buckling Checks (SESAM-Platework)

Fatigue Analysis (SESAM)

•“Screening” Lev elStochastic Fatigue Analysis using a BlanketSCF and one or more S-N Curv es with G.o.M Scatter Diagram

•Detailed Fatigue Analysis of Critical Areas using Refined FEModels (e.g. “t” x “t”)

123, 239

210,135

262, 672

368,602360,927

322, 958

Hull Structure

WebFrames

Transv. Bhd.Plating, Stiff &Girders

ShellPlating &Stiff.

Long. Bhd.Plating & Stiff.

Typical Pontoon Framing Scantlings in accordance with ClassRules (confirmed by GlobalStrength and Fatigue Analysis).

Shell Plate Thickness Limited to 22mm, except 30 mm in way of crosspontoon connections.

Plate thickness and stiffener sizevariations minimized (8 plates sizesand 7 stiffener sizes, excluding localreinforcement at foundations).

Option for bulb or angle stiffeners.

Frame Spacing: 2400 - 2950 mm.

Stiffener Spacing: 640-750 mm.

355 MPa (50 ksi) Materials.

Hull Structural Design

Global Structural Model

Hull design has adequate strength andmeets stress/buckling criteria usingreasonable plating and stiffener sizes

All areas have fatigue in excess of 200years (based on Gulf of MexicoCriteria)

Castings used in “corner” region toprovide sufficient fatigue life

Casting Detail

Moorings

Risers

Drilling Derrick

Accommodation& Utilities

Platform Configuration

TOPSIDES

Process Capacity: 100 KBOPD150 MMSCFD

Dimensions 60 x 96 x 14m

Number of Decks: 2

Operating Weight: 26,000 tonnes

HULL

Overall Length………...112 m

Overall Breadth………..95.2 m

Height (t.o. column)…..43.4 m

Draft……………………..27.5 m

Air Gap (to deck)..…….18.3 m

Process Facility

PF1C

VOID

PF1B

BALL AST

PF1A

BALL AST

PF2A

BALLAST

PF4B

BASE OIL

PF3A

BALLAST

PF5B

BALLAST

PF4A

DRILLWATER

PF5A

BALLAST

PF6A

BALLAST

ACCESS SHAFTW .T.

DOOR

SF1C

VOID

SF1BBALL AST

SF1A

BALLAST

SF2A

BALLAST

SF4B

BALLAST

SF3ABALLAST

SF4ABALLAST

SF5A

BALLAST

SF6A

BALLAST

A CCESS SHAFTW .T.

DOOR

CF1D

VOID

PA1C

VOID

PA1B

BALLAST

PA1A

BALLAST

PA2A

BALLAST

PA4B

BALLAST

PA3A

BALLAST

PA5B

BALLAST

PA4A

BALLAST

PA5A

BALLAST

PA6A

BALLAST

A CCESS SHAFT

ACCE SS SHA FTELEV.

SHAFT

P6B

BALLAST

S6BBALLAST

SF2BBALLAST

PF2B

FUEL OIL

PA2B

BALLAST

PUMPROOM

UTIL .

SHAFT

ELEV.SHAFT

PUMPROOM

UTIL .SHAFT

EL EV.

SHAFT

PUMPROOM

UTIL .

SHAFT

EL EV.SHAFT

PUMPROOM

UTIL .SHAFT

SA1A

BALLAST

SA2ABALLAST

SA4A

BALLASTSA3A

BALLAST

SA5A

BALLAST

SA6A

BALLAST

SA1B

BALLAST

SA2B

FUEL OIL

SA4B

BASE OILSA5B

BALLAST

SA1C

VOID

CA1D

VOID

SF5BBALLAST

Lower Hull Plan

CROSS PONTOONS(VOID TANKS)

PUMP ROOM (TYP)

ACCESS TUNNELS

FLUID STORAGETANKS (TYP)

Transverse Section At Corner Columns

ACCESSSHAFT

BALLASTTANK

PUMPROOM

VOID

VOID

EQPTROOM

CHAIN JACK

FAIRLEAD

VOID

PIPING/UTILITYCHASE

CROSS PONTOON

CHAIN LOCKERS

CHAIN PIPES

Transverse Section At Center Column

ACCESS TUNNEL

VOIDVOID

BALLASTTANK

BALLASTTANK

BULK TANKS

CHEMICAL

STORAGE

MUD TANKSDRILLING

FLUID

STORAGE

COLUMN STORAGE CAPACITIES

Barite/Bentonite…………425 m3 (15,000 ft3)

Cement……………………340 m3 (12,000 ft3)

Liquid Mud……………….4,000 bbls

Drilling Fluid (Brine)……4,000 bbls

Chemical Storage……….4,500 bbls

Topsides Configuration Alternatives

Integrated Deck

– Stiffened Plate “Box” Deck

– Floatover or Lifted Construction

Modular Deck

– Truss Structure

– Lifted in 4,000 ton modules orlarger

INTEGRATED “BOX” DECK

MODULAR DECK

Modular Deck Configuration

PROCESS MODULE

UPPER DECK

LOWER DECK

MEZZANINE DECK

PROCESS MODULE

Topsides - Upper (Weather) Deck

QUARTERS

RISERRACK

PIPERACK

PIPERACK SUBSTRUCT.

POWERGEN.

GASCOMPRESSION

CEMENTING/SACK STORAGE

DERRICK

FLARE

16.8 m 16.8 m19.75 m 19.75 m22.1 m

96 m

60 m

LAYDOWN/UTILITIES

FLASHGAS

BOOSTERPUMPS

Topsides - Lower (Production) Deck

QUARTERS

MUDPITS

MUDPUMPS

UTILITIES

MANIFOLD

OILPROCESS

AREA

WATERTREAMENT

UTILITIES

MCC/SWITCHGEAR

GASTREATMENT

Hull - Deck Interface

BOX BEAM

FE Model

Modular Deck Construction

Mooring And Riser System

EXPORTRISERS

PRODUCTION,INJECTION &TEST RISERS

MOORINGS

UMBILICALS

RISER PORCHES

Mooring System

SCR Interface - Production Lines

SCRFLEX JOINT/BASKET

CLEAR DECK AREA FORVERTICAL ACCESS

FIXEDPIPING

TO MANIFOLD

CHAIN JACK

CHAINBASKET

MESSENGER CHAIN

TOPSIDES

SCR LAYOUT CONCEPT

INSTALLATION SET-UP

Summary

The semisubmersible hull form provideslow motion characteristics within normaldraft limits and using a relatively simplehull geometry.

Motion response verified by analysis andmodel testing

Structural design and analysis to verifyhull weight and construction.

Efficient and functional deck layout.

Flexibility to accommodate alternativedeck construction methods.

Flexibility to accommodate riser system

Integrated Design Developmentof a

Low MotionSemisubmersible Hull Form

Thank You

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