FPSO Overall Design

7/15/2019 FPSO Overall Design

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FLOATING OFFSHORESTRUCTURES

Ship-shaped:Floating Production, Storage andOffloading Systems

OE4652 Floating Structures

Ir. H. Boonstra

Offshore Engineering



2

CONTENT

• Types

• Design drivers• Sizes

• Shapes

• General Arrangement• Systems



3

WORLD FLEET FPSO

August 2005 data (Offshore Magazine)

• 99 operating units

• About 50/50 leased/operator owned

• 15 under construction or repair/modification• 1 LPG FPSOs

• 27 units being bid

142 altogether



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FPSO DISTRIBUTION JULY 2005



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FAMILY

• Regular Tankers

• SPM Terminals

• FSU (floating storage unit)

• FSO (floating storage & offloading unit)

• FPSO• FSRU (regasification)

• LNG-FPSO (liquefied natural gas)



6

FPSO - why

• Recoverable asset

• Marginal fields (North Sea)

• Political stability (Nigeria)

• Re-use is feasible

• Lack of infrastructure (storage)

• Deep water

• Improve First Oil Date

• Parallel engineering

• Drill while you build

Anasuria



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FPSO – Layout

FALCON



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255 000 dwt



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GIRASSOL



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DESIGN DRIVERS

• Reservoir characteristics

• Field life/service life

• Site conditions

• Subsea development lay-out

• Regulatory standards & operator requirements

• Well intervention needs



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RESERVOIR CHARACTERISTICS

• Plateau production capability

• Pressure, temperature, viscosity

• Wax, asphaltenes

• CO2 and H2S content →materials, coatings

• Water cut → bpd throughput > bopd

• Gas content (GOR) → compression, gas swivel

• Water or gas injection

• Gas lift



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PRODUCTION PROFILE

Usually

peaking

up front

Water cut

influence



13

SITE CONDITIONS

• Sea surface : wind, waves, currents →

spread mooring or weather-vaning• Waves : motions, accelerations →

workability; extreme motions, stresses; fatigue

•

Current profile for risers → vortex shedding• Water depth : risers, mooring system

• Sea bed soil conditions for anchors

• Air temperature → gas turbines

possibility of ice



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SUBSEA LAY-OUT

• Direct tie-backs versus manifolding

• Turret diameter and number of risers

• Limited passes through swivel

• Swivel complexity



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STANDARDS AND CODES

• Classification Society (Lloyds, ABS, DNV, etc.)

• Coastal State

• Flag State

• International Conventions : IMO, SOLAS, MARPOL

• Detailed standards : API, ASME, ISO, ILO, etc



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VESSEL SIZE DETERMINATION

• Field production rate (bopd)

• Oil specific gravity (ton/m3, degrees API)

• Shuttle tanker schedule, days between offloading

• Sea state persistence data

• Complexity, size & weight of process plant

• Gas disposal : use, export, re-inject

• Availability of ships (for conversion)



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SHUTTLE SCHEDULE

• Regular or irregular

• Effect of weather on mooring up / disconnecting

• Mechanical breakdowns

Result : FPSO storage capacity =

bopd x shuttle interval plus a 10 - 15% reserve



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CRITERIA FOR TRANSFER source : UKOOA

500-800 m Visibility

35-40 knots35-40 knotsWind speed

15 sec15 secMax wave period

9.5 m8 mMax wave height

5.5-6.0 m4.5 mSign wave height

DisconnectConnect



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PERSISTENCE DATAexample : Gulf of Thailand

All year persistence of significant wave height

Threshold Lar er than threshold Smaller than threshold

m Duration Duration

Mean (hr) Max(hr) % of time Mean (hr) Max(hr) % of time

0.5 91 1091 69.5 49 1541 30.5

1 45 348 21.8 138 2861 78.21.5 27 185 5.7 357 6758 94.3

2 22 127 1.4 1093 7751 98.6

2.5 17 102 0.4 3009 8758 99.6

3 18 63 0.2 4373 8782 99.8

3.5 14 43 0.1 6254 8782 99.94 11 11 0 7965 8782 100



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DESIGN STEPS

• Determine total storage tank capacity

• Max. filling of tanks typically 98%

• Determine dwt capacity requirement

• Add estimated weight of the process plant

• From comparable ships, estimate main dimensions andlightweight or steelweight

• Allow for project specifics (e.g. turret)



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MAIN DIMENSIONS

• Largely determined by deadweight capacity

• Sometimes restriction of draught

• In North Sea and similar : risk of green water on deck / slamming on bow : ship shape with high freeboard atbow

• In benign areas : barge shape (cheaper to build)

L = length between pp B = width, beam

T = draft D = depth



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TANKER DWT-VOLUME RATIOTank Capaci t ies, 1923 ship s

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

0 100,000 200,000 300,000 400,000 500,000 600,000

DW T

T a n k v o l u m

e ,

t h o u s a n d b a r r e l s

Abt 7.5 bbls/ton

s.g.~ 0.84 ton/m3



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FPSO DWT-VOLUME RATIO



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STORAGE-PRODUCTION RATIO



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RESERVES-PRODUCTION

MMboe



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TANKER LENGTHLength of Tankers, 1923 ships

0,00

50,00

100,00

150,00

200,00

250,00

300,00

350,00

400,00

450,00

500,00

0 100.000 200.000 300.000 400.000 500.000 600.000

DWT

L e n

g t h b e t w e e n P P ,

215+ 0.00037 dwt

for 100-300 kdwt



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TANKER BEAMBeam of tankers, 1923 ships

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

0 100,000 200,000 300,000 400,000 500,000 600,000

Deadweight tonnage

M o u l d e d b e a m



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OIL TANKER LIGHTWEIGHT

0

0,05

0,1

0,15

0,2

0 100000 200000 300000 400000

Deadw eight Capaci ty (at full draught)

lwt/dwt

lwt/LBD

Linear (lwt/LBD)

Linear (lwt/dwt)



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DESIGN APPROACH

• Determine the required storage capacity

• Start with an “educated” guess of dimensions• Determine scantlings, based on Rules or first principles

• Check the required storage volume, weight capacity

•

Include reasonable volume for water ballast• Change dimensions and start again

The lwt/dwt statistics of tankers enable a bypass of the

cumbersome determination of scantlings



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FPSO DIMENSIONS

Always check :

• displacement = ρgCBLBT + skin, appendices• displacement = lightweight (incl. process plant) + deadweight +

suspended items (risers, anchor lines)

• deadweight = cargo weight + fuel + fluids in systems + crew +

miscellaneous• T max = D - freeboard

• Minimum freeboard determined by ship rules, for large tankersabt. 6 m

• Positive GM (GM = MB + BK – GK)



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SHAPES AND TYPES



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TYPES

• New-built or conversion

• Ship-shape or barge-shape

• Oil, LPG, LNG

• Spread moored or weather-vaning

• Internal or external turret

• Midship, bow, stern position

• Tandem or side-by-side offloading

• Gas re-injection or sales (pipeline)



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FPSO SHAPE Ship Shape•

In North Sea and similar•Green water on deck

•Risk of slamming at bow

•High freeboard at bow

•Or :because of conversion

Barge shape•Benign areas

•Cheaper to build



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CONVERSION VERSUS NEW

BUILDING

• Available time from decision to first oil

• Cost aspects

• Lifetime (fatigue considerations)

• Availability of appropriate conversion tanker

• size

• age

• history of use

• New built may be ship-shape or barge-shape



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DESIGN OF ARRANGEMENT

• Spread mooring or SPM

• SPM midship, internal in bow, external to bow

• Side or tandem offloading

• Flare tower or ground flare; position



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DESIGN OF ARRANGEMENT

• Accommodation (living quarters, LQ) : position upwind

or downwind of the process plant• Separation between LQ and flare

• Heliport unrestricted access

• Process plant subdivision• Thruster (at stern)



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MOORING

Soft Yoke (Nigeria)

Internal Turret (UK)

Spread Moored (Nigeria, risers attachedto side)

DP (China, temporarily)



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OFFLOADINGTandem

• Usually within 24 hours• Sea-state limits for mooring

up and for remaining

moored• Shuttle tanker may be

purpose built or a tanker of convenience

Side by sideSPM



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FPSO BRASIL



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255 000 dwt



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BLEO HOLM



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GIRASSOL

LNG FSRU NEW BUILT



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LNG FSRU – NEW BUILT

• SBM design

LNG FSRU CONVERSION



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LNG FSRU – CONVERSION

• SBM design



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PROCESS PLANT

PROCESS PLANT



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PROCESS PLANT

• At elevation above tank deck

• Subdivided in functional Pre-Assembled Units (PAUs), “pancakes”

• Multitude of interconnections

•Small to large

• 2 000 – 30 000 tonnes



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DEMOLITION OF EXISTING



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DEMOLITION OF EXISTING

DECK STRUCTURES

ELEVATED DECK



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ELEVATED DECK

• Typically 2.5 m above (closed) main deck

• Minimizes impact of green water

• Provides natural ventilation

• Separates (explosions in) topsides from cargo tanks

• For Northern North Sea:

Green water : elevation above still water to be taken 18-

22 m at bow, 10-12 m midship and stern



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(FPSO) PROCESS PLANT



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(FPSO) PROCESS PLANT• Separation Oil, Gas, Water

• Stabilized crude oil storage

• Gas handling – compressors, dehydration

• Water cleaning & disposal• Cooling and heating

• Flare

• Injection : gas, water, chemicals

• Gas lift

• Utilities

FIELD SPECIFIC !!



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Glas Dowr CSU load-out

STRUCTURAL WEIGHT PROCESS FACILITIES



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STRUCTURAL WEIGHT PROCESS FACILITIES

• Depends on flat versus 3D Pre-Assembled Units (PAU)

• Typically 30-40 % of total PAU weight• Self bearing structure for

• Load out

• Installation by heavy lift• Decoupling from ship’s hogging/sagging

ASSEMBLY



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ASSEMBLY

• "Pancake approach" saves time (ideally)

• .....but adds weight• Planning and logistics are essential

• Don't wait, expedite



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LIFTING PROVISIONS



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LIFTING PROVISIONS

TYPICAL COMPLETED TOPSIDES



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TYPICAL COMPLETED TOPSIDES

OIL PROCESSING MODULES



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OIL PROCESSING MODULES

Oil Separation LP

Oil Separation HP

GAS COMPRESSION MODULES



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Gas Process

Flare Stack

HP/LP Flare Knockout

Gas Compression

Gas Treatment

WATER INJECTION MODULES



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Water Treatment

Water Injection

STEAM / POWER



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Power Generation

Steam Generation

/

GENERATION



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FPSO SYSTEMS

Safety

Cargo Handling

Miscellaneous

Operation

Support Systems

SAFETY



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Fire and Gas

Emergency shut downDeluge

Safe Haven / Temporary Refuge

Emergency lighting Access and escape

Life boats, life rafts, helicopter

Seabed safety valve

FIRE FIGHTING



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• Pressurized fire mains throughout ship

•

Deluge system in specific areas• Sprinkler system in accommodation

• CO2 or other system in ship engine room

• Foam system on helideck

• Main fire pumps + jockey pump• Diesel driven emergency fire pump

• Fire & Gas detection system, monitored in CCR

ACCESS & ESCAPE



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• Main access by helicopter

• Heliport includes safety induction room• Escape by helicopter or boat

• conventional closed life boats

•free fall boats

• Life rafts as required by IMO

• Fast Rescue Craft

OPERATION



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Central Control Room

Power generation

Power distribution

Uninterruptable Power Supply

Remote cargo valve control

Material handling / laydown

Fresh/potable water

Tank monitoring

CARGO HANDLING



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Crude distribution

Tank monitoringFiscal metering

Offloading

Inert gas & tank ventilationBallast

Corrosion protection

CARGO



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• Central pumproom or deepwell/submersible pumps

• Single or multiple segregations

• Tank level gauges

• Settling tank(s)

• Slop tank(s)

• Cargo control system

• Remote control of valves

• Sloshing and free surface effects

CRUDE STORAGE TANKS



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• Storage tanks for 5-10-20 days peak production

• Storage for off-spec production• Max size per tank 30,000 m³ (MARPOL)

• Slop tank(s)

•

Segregated ballast tanks• Double hull principle : not (yet) required for FPSO

• Volatile Organic Compounds (VOC) control in crudetanks

INERT GAS



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• Purpose : preventing explosive conditions

• IG generator or stack exhaust gas• VOC’s depend on crude composition

• Crude flammability grade A-E depends on vapor

pressure (RVP measured at 31.8° C) and flash point• Lighter crude usually is more flammable

BALLAST



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• Purpose : draft and trim control

• Always segregated ballast tanks• Mainly wing tanks + peak tanks

• Corrosion protection

•

Inspection

OFFLOADING



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• Tandem shuttle mooring

• hawser• offloading hose

• quick release provisions

•

shuttle collision risk • Side by side shuttle mooring (unusual)

• Separate SPM berth (spread moored FPSO)

•

Fiscal metering system

GLAS DOWR



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Reel for theoffloading hose



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GLAS DOWR

Offloading hose reel

GLAS DOWR



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Bunker hose and hawser reels

TANDEM OFFLOADING TO



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MIDSHIP

SUPPORT SYSTEMS



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Pig launcher & receiver

Material handlingCrude oil washing

Anchor line tensioning

Cooling & heatingDrain systems

UTILITIES



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• Neither ship nor process

•Power plant for compressors, process etc

• Disposed water treatment

MATERIAL HANDLING



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• Deck crane(s)

•Lay down area(s)

• Trolleys, deck equipment

• Swivel module handling system

MISCELLANEOUS



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Accommodation

Communications and Public Address System

Shipboard power distributionHVAC

Seawater

Fresh water

Grey water, sewage treatment, incinerator

Fuel, lubrication oil

Thruster

ACCOMMODATION



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• Position of living quarters upwind or downwind of

process area• Safe Haven /Temporary Safe Refuge

• Central Control Room

• Client cabin(s) and office

• Temporary accommodation of larger maintenancecrews

HVAC (heating, ventilation, air-conditioning)



87

• Forced ventilation in living quarters and hull

•

Natural ventilation of process plant• HVAC designed for worldwide conditions

• Flaps in air ducts close on fire alarm

FUEL & LUB OIL



88

• Concentrated in ship’s engine room

•

Diesel pipeline to gas turbines in utilities• Supply by supply boat or shuttle tanker

FRESH WATER



89

• Fresh water makers on waste heat or board net

•

Sewage treatment unit• Engine cooling may be on closed fresh water circuit

THRUSTER(S)



90

• Requirement with midship turret

•

Sometimes with bow turret• Automatic thrust control, heading feedback

Documents

FPSO Overall Design