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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
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
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