Pigging Slug Trick

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Pigging Slug Trick

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  • 1Primary funding is provided by

    The SPE Foundation through member donations and a contribution from Offshore Europe

    The Society is grateful to those companies that allow their professionals to serve as lecturers

    Additional support provided by AIME

    Society of Petroleum Engineers Distinguished Lecturer Programwww.spe.org/dl

  • 2Slugging in Pipelines:What You NEED to Know

    Mona TrickAdvisor Flow Software

    Schlumbergermtrick@slb.com

  • 3Outline

    Why Worry? Hydrodynamic Slugs Terrain Induced Slugs Turn Up Slugs Pigging Slugs Slug Modelling: Where Are We? Areas Currently Being Researched Conclusions

  • 4Why Worry?

    Damage to facilities

    Separators flooding

    Increased corrosion

    Starving compressors

    High back pressures

  • 5Hydrodynamic Slugs

    Slugs can be created by just flowing

    and there might be lots of them

    Steady state mechanistic models will account for hydrodynamic slugging (OLGAS, XIAO models)

  • 6Hydrodynamic Slugs

    25

    26

    27

    28

    0.0 0.5 1.0

    Time hours

    Liquid Inventory m3

    6300

    6400

    6500

    6600

    6700

    Inlet Pressure kPa

  • 7Avoiding Hydrodynamic Slugs

    Superficial Gas Velocity (ft/sec)

    Supe

    rfic

    ial L

    iqui

    d Ve

    loci

    ty (f

    t/sec

    )

    Bubble

    Slug Wave

    0.01 0.1 1 10

    0.01

    0.1

    1

    10

    100

  • 8A Slug can be created by liquid trapped in the pipeline at low spots

    Terrain Induced Slugs

    .. Irregular ...

  • 9Severe SluggingStage 1

    Terrain Induced Slug - Severe

    Gas blockage can occur in downward sloped flow line at riser base

    A liquid slug begins to form in the riser

    GasLiquid

  • 10

    Terrain Induced Slug - Severe

    Riser fills, and liquid begins to unload into the separator

    Gas pressure builds up behind slug!!!

    Severe SluggingStage 2

    GasLiquid

  • 11

    Severe SluggingStage 3

    Terrain Induced Slug - Severe

    Gas penetrates into the riser

    Liquid begins to unload rapidly

    GasLiquid

  • 12

    Severe SluggingStage 4

    Terrain Induced Slug - Severe

    Liquid blows through with residual fallback

    Gas blockage occurs, and cycle begins again

    GasLiquid

  • 13

    Terrain Induced Slug

    Steady State Multiphase Software: Severe slugging: Fuchs and Pots

    correlations give contradictory results but Pots can give indication of potential severe slugging

    Cannot predict other terrain induced slugging Check for high liquid holdup in low spots and

    low liquid velocities

  • 14

    Terrain Induced Slug

    Use a Transient Multiphase Model to Determine:

    Whether terrain induced slugging will occur Length and size of slug Transit time of slug Frequency of slug Separator size required to handle the slug

  • 15

    Severe Slugging Liquid Flow Rate

    0

    500

    1000

    1500

    2000

    2500

    0.0 0.5 1.0 1.5 2.0

    Time hours

    Outlet Liquid Rate m3/d

    5500

    6000

    6500

    7000

    7500

    Inlet Pressure kPa

  • 16

    Separator Size

  • 17

    Avoiding Terrain Induced SlugsIn Onshore Pipelines: Increase gas flow rates Decrease diameter

    In Offshore Risers:

    Add riser base gas injection

    Increase backpressure

  • 18

    Turn Up SlugsA Slug can be created by a Flow Rate change

    .

    .. but only when it increases ...Slug volume = difference between liquid holdup at 2 flow ratesUse transient model to rigorously model

  • 19

    Turn Up Slugs

    0

    200

    400

    600

    800

    1000

    1200

    0.0 1.0 2.0 3.0 4.0

    Time hours

    Outlet Liquid Rate m3/d

    6600

    6700

    6800

    6900

    Inlet Pressure kPa

  • 20

    Pigging SlugsSlugs can be created by Pigging

    .. but typically just one...

    Slug volume = total liquid in pipe minus volume dumped into the separator during pig transit

    Use transient multiphase model to accurately model pigging slug size and transit time

  • 21

    Pig Position and Pig Velocity

    0

    2

    4

    6

    8

    0.0 0.5 1.0 1.5

    Time hours

    Pig Position km

    0

    1

    2

    3

    4

    Pig Velocity m/s

  • 22

    Liquid Inventory from Pigging

    0

    10

    20

    30

    40

    50

    60

    70

    0 2 4 6 8 10

    Time hours

    Liquid Inventory m3

    6400

    6450

    6500

    6550

    6600

    6650

    6700

    Inlet Pressure kPaa

  • 23

    Slug Modelling: Where are We?

  • 24

    Slug Modelling: Where are We?

  • 25

    Slug Modelling: Where are We?Mechanistic Models Use the Unit Cell Model

    Developed by Taitel in 1980s

    Liquid picked up from liquid film = liquid shed

    In mechanistic models now (OLGAS, XIAO)

    Accurate pressure gradients and holdup

    in fully developed slugs

  • 26

    Areas Currently Being Researched

    Flow pattern transition to / from slug flow in steady state

    More robust models for Liquid holdup in liquid slug (gas entrainment) Gas velocity in liquid slug (turbulence within

    the liquid slug) Liquid holdup in elongated bubble Liquid slug translational velocity

  • 27

    Conclusions

    Define what you mean by slugging- hydrodynamic- terrain induced- turn up- pigging

    Transient modelling provides additional information

    Mechanistic modelling of slug flow understood but still actively being researched and improved

  • 28

    Acknowledgements

    Dr. Garry Gregory and Dr. Khalid Aziz For creating the multiphase video at the

    University of Calgary For the images for severe slugging and slug

    flow Pablo Adames, Schlumberger

    For updates on the current state of slug research and parsing the multiphase video

    Schlumberger for sponsoring My time, visas, inoculations and hotels

  • 29

    Society of Petroleum Engineers Distinguished Lecturer Programwww.spe.org/dl

    Your Feedback is Important

    Enter your section in the DL Evaluation Contest by completing the evaluation form for this presentation

    http://www.spe.org/dl/

    29

  • 30

    Slugging in Pipelines:What You NEED to Know

    Mona TrickAdvisor Flow Software

    Schlumbergermtrick@slb.com

  • 31

    Hydrodynamic Slugging: Steady State

  • 32

    Hydrodynamic Slugging: Transient

  • 33

    Hydrodynamic Slugging: Transient

  • 34

    Terrain Induced Slugging

  • 35

    Terrain Induced Slugging

  • 36

    Turn Up

  • 37

    Turn Up: Elevation Profile

  • 38

    Pigging

    Slide Number 1Slugging in Pipelines:What You NEED to KnowOutlineWhy Worry?Hydrodynamic SlugsSlide Number 6Avoiding Hydrodynamic SlugsTerrain Induced SlugsTerrain Induced Slug - Severe Terrain Induced Slug - SevereTerrain Induced Slug - SevereTerrain Induced Slug - SevereTerrain Induced SlugTerrain Induced SlugSevere Slugging Liquid Flow RateSeparator SizeAvoiding Terrain Induced SlugsTurn Up SlugsTurn Up SlugsPigging SlugsPig Position and Pig VelocityLiquid Inventory from PiggingSlug Modelling: Where are We?Slug Modelling: Where are We?Slug Modelling: Where are We?Areas Currently Being ResearchedConclusionsAcknowledgementsSlide Number 29Slugging in Pipelines:What You NEED to KnowHydrodynamic Slugging: Steady StateHydrodynamic Slugging: TransientHydrodynamic Slugging: TransientTerrain Induced SluggingTerrain Induced SluggingTurn UpTurn Up: Elevation ProfilePigging