Flow assurance using AspenHYSYS Hydraulics

ProcessSimulationFlowAssuranceCaseStudy

2014©COPYRIGHTPROCESSECOLOGYINC.

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EstimationofslugvolumeusingAspenHydraulics

Background

• Heavyfractioninnaturalgascondensesmayresultinslugsreachingfacilities

• Sizingtheslugcatcherrequiresestimationofslugvolumeandduration

23/04/14 2014©COPYRIGHTPROCESSECOLOGYINC.

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Projectdescription

• Muchrichergaswasexpectedintheclientpipeline.

• Theobjectiveofthisprojectwastoestimatetheanticipatedslugvolumeandduration

• Initialestimatesindicateda3,000bbl vessel


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Sluggingtypes

• Terrain–inducedslugging– Causedbychangeofelevationinpipeline.

• Hydrodynamicslugging– Causedbyformationofwaveonliquidsurfaceasaresultoffastermovinggasphase.

• Pig-Inducedslugging– Causedbypiggingoperationsinpipeline.Pigisdesignedtopushmostoftheliquidcontentstotheoutlet.


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Slugvolumepredictionmethods

• Basedonthecompositionandoperatingconditionsatslugcatcher

• UsingAspenHYSYSPipesegmentsluganalysistool(Hydrodynamicslug)

• Estimationusingliquidhold-upprofile(Pig-Induced)

• TransientanalysisusingAspenHydraulics(Terrain-Induced,Pig-Induced)


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Elevationprofile

73and47pointswereselected(asabalancebetweenaccuracyandmodelspeed)torepresentPipe1andPipe2respectively.

ValidationCase

Location Pressure(kPa)Reported HYSYSPipe

Pipe1-60KMfromInlet 5,099 5,130Compressor1Suction 4,998 5,011Compressor1Discharge 6,486 6,657

Pipe2-40KM fromCompressor1Station

5,901 5,911

Compressor2Suction 5,026 5,026(spec)Pipe1pressuredrop 101 119Pipe2pressuredrop 1,460 1,631


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Pipe2a30KM

Pipe1140KM

CompressorStation1

Pipe2b50KM

CompressorStation2

Assumptions:Thegroundtemperaturewasassumedtobe4C.Thepipedepthwasassumedtobe2m.

SlugPrediction

• Recoveredliquidvolumeflowratefromflashcalculation

• Slugvolumebasedontheliquidholdupprofile• SlugVolumebasedontransientanalysisusingHYSYSHydraulics


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SlugPrediction




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Gascomposition

• Clientprovided3compositionsforcurrentcase,OneyearprospectandUltimate.


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Analysis Methanecontent(mol%)

Current 90.59

OneyearProspect 86.91

Ultimate 79.50

Flashcalculationresults

Analysis RecoveredLiquid(bbl/day)@29.5Fand530psigUnadjustedcomposition Adjustedheavycomposition

Current 0 366OneyearProspect 101 338Ultimate 0 345


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• Thevaluesinthistablerepresenttheanticipatedsteady-stateliquidproduction.

• RecoveredliquidisstrongfunctionofC6+composition.Clientwasadvisedtogetanextendedanalysisforthecurrentproductionwhichmay providesomeguidanceregardingtheexpectedC6+representationforfutureproduction.

SensitivityAnalysis– C6+/C7+distribution


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• Theprovidedcompositionforthe“Oneyearprospect”contained500ppmofC7+,whichwasassignedtoC9andC10respectively

SlugPrediction




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Liquidholdupprofile


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0

0.0005

0.001

0.0015

0.002

0.0025

0 10000 20000 30000 40000 50000 60000 70000 80000

Liqu

idholdu

p

DistancefromCompressor1discharge(m)

Pipe2(A/B)liquidholdupprofile

𝐸" = 𝐴% 𝐿'() − 𝐿' ℎ𝑜𝑙𝑑𝑢𝑝 '2

'3)

Slugvolumebasedonliquidholdupprofile

• 𝑉5678 = 𝐸" − 𝑄" ∗ 𝑃𝑖𝑔𝑇𝑟𝑎𝑛𝑠𝑖𝑡𝑇𝑖𝑚𝑒


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Pipe1 Pipe2PigTransitTime(hrs) 20 2Method SlugVolume(bbl)HYSYS-HTFS-LiquidSlip 102 9HYSYS-HydraulicPipe(SS) 98 8FanandDanielson(ConocoPhilips)

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SomecommentsforwhywelookedatPipe1

Pipe1liquid-gasproductionis1/3ofPipe2--->Lowerphasevelocities--->Higherliquidaccumulation--->Higherpig-inducedslug

SlugPrediction


• Slugvolumebasedonsteadystateliquidholdupprofile

• SlugVolumebasedontransientanalysisusingHYSYSHydraulics– AspenHydraulicsallowsyoutosimulatethepiggingrigorouslyindynamicmode.


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Modelsetup


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- Steady-statevaluesforinitializationofdynamicsmode- Usedsteady-statetemperatureprofileanddisabledheattransfercalculationsinthe

dynamicsmode- UsedEventSchedulertorunthepigs- HighPerformancePig

SlugVolume- Transientmodelling


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- Peakof~550bbl/day- Mostoftheliquidisrecoveredwithin1-2hours

Pressuredrop– Transientmodelling


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500

550

600

650

700

750

1440 2440 3440 4440 5440 6440 7440 8440

PressureDrop(kPa

)

ElapsedTime(min)

PressuredropinPipe2b

Piggingfrequency


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Pigging Interval (hrs) Pigging Slug Size (bbl)Pipe1

1 1.75 8.712 20.824 41.648 83.172 100.378 101.5

PiggingInterval(hrs) PiggingSlugSize(bbl)Pipe2

1 10.13 30.25 44.37 50.010 50.1

EffectofPipe1slugonslugcatcher


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0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

0 10000 20000 30000 40000 50000 60000 70000 80000

Liqu

idholdu

p

DistancefromCompressor1Discharge(m)

Steady-stateholdupprofileinPipe2

Holdupprofile5hoursafterPipe1slugsenttoPipe2

Conclusions

• Resultsarehighlysensitivetothecompositionofheavycomponents

• Aconservativedesignwouldlimitthesizeofthevesseltoaround1,000bbl

• AspenHYSYSenablestheestimationofslugvolumeswithvariouslevelsofdetail

• HYSYSUpstreamHydraulicsallowstheevaluationoftransientslugformation


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Thankyouforyourattention

• QUESTIONS?

• [email protected]• [email protected]


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Gascomposition

GasComposition(mol%)CurrentCase Oneyearprospect Ultimate

AsGiven

Heavy AsGiven Heavy AsGiven Heavy

Methane 90.59 90.59 86.91 86.91 79.50 79.50Ethane 5.84 5.84 8.41 8.41 15.55 15.55Propane 1.95 1.95 2.47 2.47 3.23 3.23i-Butane 0.26 0.26 0.38 0.38 0.27 0.27n-Butane 0.37 0.37 0.52 0.52 0.43 0.43i-Pentane 0.05 0.05 0.12 0.12 0.03 0.03n-Pentane 0.05 0.05 0.09 0.09 0.03 0.03n-Hexane 0.04 0.04 0.07 0.07 0.05 0.05n-Heptane N/A 0.00 0.04 0.03 N/A 0.00n-Octane N/A 0.00 0.01 0.01 N/A 0.00

C9 N/A 0.00 0.00 0.00 N/A 0.00C10+ N/A 0.04 N/A 0.01 N/A 0.03

Nitrogen 0.52 0.52 0.43 0.43 0.44 0.44CO2 0.29 0.29 0.55 0.55 0.44 0.44Sum 99.96 100.00 100.00 100.00 99.97 100.00


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Flow assurance using AspenHYSYS Hydraulics

Engineering

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