Offshore Platforms Sizing Offshore Platforms Sizing Optimization through Genetic Optimization through Genetic

Algorithms Algorithms

Mauro Costa de OliveiraMauro Costa de OliveiraPetrobrasPetrobras

DeepDeep WaterWater FloatingFloating ProductionProductionSystemSystem

HowHow to to selectselect thethe bestbestdimensionsdimensions//shapeshape for for thethe floaterfloater??

BestBest PlatformPlatform ShapeShape andandDimensionsDimensions

BestBest PlatformPlatform ShapeShape andandDimensionsDimensions

BestBest PlatformPlatform ShapeShape andandDimensionsDimensions

DeepDeep WaterWater FloatingFloating ProductionProductionSystemSystem PlatformPlatform Design Design BasisBasis

DeepDeep WaterWater FieldField ScenarioScenario–– OilOil CharacteristicsCharacteristics–– EnvironmentEnvironment, , SoilSoil–– InfrastructureInfrastructure

ProcessProcess PlantPlant CharacteristicsCharacteristicsSubseaSubsea SystemSystem InterfaceInterfaceBuilding RequirementsBuilding RequirementsRules and RegulationsRules and Regulations

Design Design ProcessProcess

Selection of the main dimensions of a deep water Selection of the main dimensions of a deep water floating production system can be an exhaustive floating production system can be an exhaustive trial and error exercise;trial and error exercise;

A rational approach to guide the designer in this A rational approach to guide the designer in this search can be very usefulsearch can be very useful

Develop an organized searching processDevelop an organized searching process

MainMain Design Design ParametersParameters

ProcessProcess plantplant weightweight andand areaarea;;SubseaSubsea SystemSystem Interface;Interface;StabilityStability;;MotionsMotions (SCR);(SCR);BuildingBuilding//InstallationInstallation ConstraintsConstraints;;Internal Compartments Volume and Internal Compartments Volume and Distribution;Distribution;

ProcessProcess PlantPlant AreaArea andandArrangementArrangement

WeightWeight

BuildingBuilding ConstraintsConstraintsQuayQuay ConditionsConditions

BuildingBuilding ConstraintsConstraintsDeckDeck MatingMating

Transit ConditionTransit Condition

SubseaSubsea SystemSystem InterfaceInterface

SubseaSubsea Interface Interface SteelSteel CatenaryCatenary RiserRiser

Sea BedSea Bed

PLEMPLEMFlowlineFlowlineSCRSCR

Flex JointFlex Joint

Wat

er D

epth

Wat

er D

epth

StabilityStability

InitialInitial StabilityStability –– MetacentricMetacentricHeightHeight (GM)(GM)IMO CriteriaIMO Criteria

MotionsMotions in in WavesWaves

Fatigue Fatigue SeaSea States States SteelSteel CatenaryCatenary RisersRisers

point wave direction case

(from where it comes)Hs(m) Tp(s) alfa gama of vertical motion(m)P1 south 2.75 11.71 0.0019 1.16 02s05aP2 south 2.75 11.71 0.0019 1.16 02s05aP3 south 2.75 11.71 0.0019 1.16 02s05aP4 south 2.75 11.71 0.0019 1.16 02s05aP5 south 2.75 11.71 0.0019 1.16 02s05aP6 south 2.75 11.71 0.0019 1.16 02s05aP7 south 2.75 11.71 0.0019 1.16 02s05aP8 south 2.75 11.71 0.0019 1.16 02s05a

0.20560.17680.180.18

seastate category #1 - fatigue medium swellwave data (Jonswap spectrum) max. standard deviation

0.20560.20560.17680.1768

P1 P5

P6 P3

P7

P3

P2

P2

P1

P8

P4P4

NORTH

P1 P5

P6 P3

P7

P3

P2

P2

P1

P8

P4P4

NORTH

InternalInternal CompartmentsCompartments

BallastBallast AmountAmountEquilibriumEquilibrium in in ParallelParallel DraftDraft

Some Some AlternativesAlternatives to to SelectSelect thetheBestBest DesignDesign

““Manual” Evaluation of Some DesignsManual” Evaluation of Some Designs

AutomaticAutomatic GenerationGeneration ofof SeveralSeveral DesignsDesigns–– DrawDraw backback: : UnfeasibleUnfeasible designsdesigns–– AnalysisAnalysis andand selectionselection ofof thethe datadata

OptimizationOptimization–– GeneticGenetic AlgorithmsAlgorithms

Performance Performance TestsTests

SCR Fatigue Motions < Fixed

LimitsHydrodynamic

GM > 0.0 mGM > 0.3 mGM > 2.0 mInitial Stability

Parallel Draft

Equilibrium

Parallel Draft

Equilibrium

Parallel Draft Equilibrium /

Volume of Ballast > 15% of the Displacement

Loading Cond. / Ballast

Quay Condition

Transit Condition

Operation Condition

OptimizationOptimization ProcedureProcedure

Tool used to carry out the optimization process Tool used to carry out the optimization process was the program was the program ModeFrontierModeFrontier from ESTECOfrom ESTECO;;Genetic Algorithm Genetic Algorithm NSGANSGA--II scheduler;II scheduler;Develop a prescribed number of generations Develop a prescribed number of generations with a fixed number of memberswith a fixed number of members;;CoupleCouple thethe geneticgenetic algorithmalgorithm withwith thethe analysisanalysisprogramsprograms;;

OptimizationOptimization ProcedureProcedure

INPUT DATA

STABILITY ANALYSIS

OUTPUT DATA

MOTION ANALYSIS

OptimizationOptimization ProcedureProcedureInput Input VariablesVariables

OptimizationOptimization ProcedureProcedureInput Input VariablesVariables

2.517400Platform Heading related to NorthHEADING (degrees)

0.2764025DraftDRAFT (m)

2.497252.8Length of Transv and

Longit Pontoons between columns

LONG_PONTOON_LENGTH

(m)

0.626216Pontoon HeightPONTOON_DEPTH(m)

0.630279.6Longit Pontoon and Column Breadth

LONGIT_BREADTH(m)

StepBaseUpperBound

LowerBoundDescriptionName

ConstraintsConstraints

Dimensions / Volume / Quayside Draft

52.7GreaterMinimum Pontoon Length95LesserMaximum Total Length70GreaterMinimum Total Length

84500LesserMaximum Displacement0.32LesserMaximum Amount of Ballast0.18GreaterMinimum Amount of Ballast

0.5GreaterMinimum Freeboard in Quay Condition

11LesserMaximum Quay Draft

ConstraintsConstraints

Minimum GMt / GMl

0.3GreaterTransit Condition1GreaterQuay Condition

1.9GreaterOperating Condition

ConstraintsConstraints

Maximum Vertical Motion at SCR Connection Points

0.321LesserP1B Sea 3.75 m 12.08 s

0.23LesserP2A Sea 2.75 m 11.71 s0.23LesserP2B Sea 2.75 m 11.71 s

0.321LesserP1A Sea 3.75 m 12.08 s

0.321LesserP2A Sea 4.25 m 11.70 s

0.23LesserP1B Sea 2.75 m 11.71 s

0.23LesserP1A Sea 2.75 m 11.71 s

ObjectivesObjectives

The minimization of the vertical motion RMS The minimization of the vertical motion RMS in points P1A and P3 with the south and in points P1A and P3 with the south and southwest sea statessouthwest sea states

P1 P5

P6 P3

P7

P3

P2

P2

P1

P8

P4P4

NORTH

P1 P5

P6 P3

P7

P3

P2

P2

P1

P8

P4P4

NORTH

SummarySummary

1.1. Define 5 input variablesDefine 5 input variables2.2. Generate the hull, internal compartments, lightweight Generate the hull, internal compartments, lightweight

and variables loadsand variables loads3.3. Evaluate Quay Condition Equilibrium and Initial StabilityEvaluate Quay Condition Equilibrium and Initial Stability4.4. Evaluate Transit Condition Equilibrium and Initial Evaluate Transit Condition Equilibrium and Initial

StabilityStability5.5. Evaluate Operating Condition Equilibrium and Initial Evaluate Operating Condition Equilibrium and Initial

StabilityStability6.6. Evaluate Extreme Motions and Fatigue MotionsEvaluate Extreme Motions and Fatigue Motions7.7. Extract Output DataExtract Output Data8.8. Return to the BeginningReturn to the Beginning

ResultsResults5046 designs generated;5046 designs generated;672 different ones;672 different ones;35 feasible;35 feasible;563 unfeasible;563 unfeasible;74 failed in the equilibrium;74 failed in the equilibrium;

ResultsResults

ResultsResults

ResultsResults

ResultsResults

0HEADING (degrees)

36.4DRAFT (m)

52.8LONG_PONTOON_LENGTH (m)

9.6PONTOON_DEPTH (m)

18LONGIT_BREADTH (m)

ValueInput Variables

ResultsResults

ResultsResults

24698.81Steel Structure WeightSTEEL WEIGHT (t)12.08Buoyancy HeightKB (m)28.48Height of CoGKG (m)

84458.77DisplacementDISPLACEMENT (t)0.226Ballast AmountBALLAST (%)88.8Total LengthTOTAL_LENGTH (m)2.52Oper GM LongitGM_LONG (m)

0Oper HeelHEEL (degree)0Oper TrimTRIM (degree)

2.52Oper GM TransvGM_TRANS (m)

ValueDescriptionOutput Variables

ConclusionConclusion

Optimization Procedure is Feasible to Use in the Optimization Procedure is Feasible to Use in the Selection of Main Dimensions of a Deep Water Selection of Main Dimensions of a Deep Water FloaterFloaterFurther questions:Further questions:

Mauro Costa de OliveiraMauro Costa de Oliveira((mauro@petrobras.com.brmauro@petrobras.com.br))

Thank youThank you