bhrg 2009 no_backup

www.bhrgroup.co.uk

14th International Conference Multiphase Production Technology

Cannes, France - 17th - 19th June 2009

SDAG

Discretization Methods for Multiphase Flow Simulation of Ultra-Long Gas-Condensate Pipelines

Erich Zakarian & Henning HolmShtokman Development A.G.

14th International Conference Multiphase Production TechnologyCannes, France - 17th - 19th June 2009

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Contents

• The Shtokman field development

• Profile discretization of gas-condensate pipelines• Objective and requirements• Method 1 – concept of pipeline profile indicator• Method 2 – concept of lumping and redistribution• Comparison and simulation

• Conclusions


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Integrated Development of the Shtokman Gas-Condensate Field – Phase 1


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Cannes

ParisMurmansk

Teriberka

Shtokman

Gas export to shore • 70 MSm3/d (2.5 BCFD) – Phase 1• 2 x 36” ND trunklines (0.86 m ID)• Length 558 km (347 miles)• Dry two-phase flow• CGR = from 2 to 16 Sm3/MSm3


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-400

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-100

0

100

200

0 100 200 300 400 500Distance [km]

Elev

atio

n [m

]

Shtokman pipeline profile

• Detailed pipeline profile from seabed bathymetry survey (2007)

• Free span analysis and seabed intervention taken into account

108,785 points


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Given either as-built profile or detailed terrain survey

• In transient multiphase flow simulation, the actual or expected pipeline geometry must be simplified to achieve reasonable CPU time

• For long pipelines (> 100 km) laid on rough terrain, compression of a large set of data points is required typically from 104-105 points to few 103 points

Pipeline profile discretization: objective

Target Simulation time ≥ 24 x CPU time


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The Shtokman case

• Average pipe length will be approximately 200 m

• Avoid small pipe sections to maximize numerical time steps

Δt < min (Δx/U)i

Target ≈ 2500 pipesfor a total length of 554 km


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Pipeline profile discretization: requirements1. The total pipe length must be conserved

2. The simplified geometry must have the same overall shape (large and small scale undulations)

3. The pipe angle distribution of the discretized profile must be as close as possible to the original distribution

4. The total climb (cumulative length of uphill pipes) must be conserved to predict the same overall liquid content in steady-state flow conditions

1

24

3

Original profile


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Liquid holdup vs. pipe inclination

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

-5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10Pipe inclination [deg]

Liqu

id h

oldu

p [-]

USG = 1.00 m/s

USG = 1.50 m/s

USG = 2.00 m/s

USG = 2.50 m/s

USG = 3.00 m/s

USG = 3.50 m/s

USG = 4.00 m/s

USG = 4.50 m/s


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Two methods for a single objectiveMethod 1: concept of pipeline profile indicator

• Select, simplify and complexify relevant sub-profiles

• Use the pipeline profile indicator and the total climb to match the original angle distribution

Method 2: concept of lumping elements with similar inclination

• Redistribution to match the original large & small scale topographies


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Method 1

Concept of pipeline profile indicator


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Definition: pipeline profile indicator

θi = inclination of pipe i with respect to horizontal [%]Li = length of pipe i [m]N = number of pipes

B. Barrau, “Profile indicator helps predict pipeline holdup, slugging”, Oil & Gas Journal Vol. 98, Issue 8, p. 58-62, Feb 21, 2000

( ) ( )[ ] 25066091490 ...tan.+−×= ii ArcHoldup θ

πθ

( ) ( )[ ]1000

0

1

1 ××−

=

∑

∑

=

=N

ii

N

iii

L

LHoldupHoldupPI

θ


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Holdup function vs. OLGAS

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

-5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10Pipe inclination [deg]

Liqu

id h

oldu

p [-]

Holdup function

USG = 1.00 m/s

USG = 1.50 m/s

USG = 2.00 m/s

USG = 2.50 m/s

USG = 3.00 m/s

USG = 3.50 m/s

USG = 4.00 m/s

USG = 4.50 m/s


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Pipeline profile indicator scale

PI < 0 Pipeline profile is globally sloping downwardsNo particular operating problem to be expected

0 < PI < 20 Pipeline profile is nearly horizontal or over-simplifiedNo particular operating problem to be expected

20 < PI < 40 Pipeline profile is relatively flat or slightly hillyPossible troubles at very low flow rates or during restart

40 < PI < 80 Pipeline crosses hilly terrainDesign & Operation needs particular attention

80 < PIPipeline profile is very hilly or very steepDesign & Operation needs very careful attentionValidity of simulation software to be checked

From Total E&P experience in gas-condensate pipelinedesign and operation

Shtokman pipeline profile indicator = 79.7


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Step 1: sub-profile selection

020406080

100120140160180

0 100000 200000 300000 400000 500000

Pipe

line

indi

catto

r [-]

Distance from offshore platform [m]

-10-8-6-4-202468

10

230000 240000 250000 260000 270000 280000

Incl

inat

ion

[deg

]


Pipe inclination

-10-8-6-4-202468

10

410000 420000 430000 440000 450000 460000

Incl

inat

ion

[deg

]


Pipe inclination


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• Final average pipe length should be about 200 m (target ≈ 2500 pipes)

• For example, use the Box Filter from OLGA®

Geometry Editor

• Or simply select one point every 1 km

Step 2: simplification of the original profile


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0500100015002000250030003500400045005000

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0

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0 100000 200000 300000 400000 500000

Total climb [m

]Elev

atio

n [m

]


Pipeline geometryPipe elevation (simplified profile) [m]Pipe elevation (original profile: 108,785 points) [m]Total climb (original profile: 108,785 points) [m]Total Climb (simplified profile) [m]

-15-10

-505

101520

0 100000 200000 300000 400000 500000

Incl

inat

ion

[deg

]


Pipe inclinationPipe inclination (original profile: 108,785 points) [deg]Pipe inclination (simplified profile) [deg]

PI = 79.7 25.8

Step 2: result


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Step 3: complexification

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0 2000 4000 6000 8000 10000


Elev

atio

n [m

]

Complexified profile

Simplified profile

For each sub-profile• Keep original pipeline

indicator within +/-1%• Keep original total climb

within +/- 1%

• Split the simplified profile into smaller pipes5 smaller pipes per simplified pipe pipe length ≈ 200 m

• Move new points up and down with a random process


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0500100015002000250030003500400045005000

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-200

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0

100

200

0 100000 200000 300000 400000 500000

Total climb [m

]Elev

atio

n [m

]


Pipeline geometryPipe elevation (complexified profile) [m]Pipe elevation (original profile: 108,785 points) [m]Total climb (complexified profile) [m]Total climb (original profile: 108,785 points) [m]

-15-10

-505

101520

0 100000 200000 300000 400000 500000

Incl

inat

ion

[deg

]


Pipe inclinationPipe inclination (original profile: 108,785 points) [deg]Pipe inclination (complexified profile) [deg]

Step 3: result


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Method 2

Concept of lumping elements with similar inclination


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Method 2 – “Lumping and redistributing”

1. Define the criteria (in priority) to determine the pipe length to be used for the simplified profile :1. minimum pipe length2. maximum elevation change for a pipe element3. maximum pipe length

2. Sort all elements in the detailed profile by inclination in ascending order

3. Lump together the sorted elements to longer pipes, starting with the element with the steepest downhill inclination. The length of each pipe element is then limited by dominating criteria in 1).

4. Distribute the pipe elements in the simplified profile to match the large scale and small scale topography of the detailed profile.


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Pipelength (m)

Pipe

ele

vatio

n ch

ange

(m)

Xmin Xmax

Maximum elevation change

-25-20-15-10

-505

10152025

-8 -6 -4 -2 0 2 4 6 8Pipe inclination (deg)

Elev

atio

n ch

ange

(m)

01002003004005006007008009001000

Pipe

leng

th (m

)

Elevation change of single pipePipe length

Step 1)Define the criteria (in priority) to determine the pipe length to be used for the simplified profile :1. minimum pipe length (200 m)2. maximum elevation change for a pipe element (5 m)3. maximum pipe length (1000 m)


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Step 3)Lump together the sorted elements to longer pipes, starting with the element with the steepest downhill inclination. The length of each pipe element is then limited by dominating criteria in 1).

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0

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Distance (m)

Ele

vatio

n (m

)

-1200-1100-1000-900-800-700-600-500-400-300-200

0 50000 100000

Distance (m)

Elev

atio

n (m

)

-5-4-3-2-1012345

Incl

inat

ion

(deg

)Original profile

Inclination

Lumped, but not redistributed profile

Step 2) Sort elements in the detailed profile by inclination in ascending order – divide into subsections if required


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”Inclination classes” versus ”lumping by inclination in ascending order ”

0

100000

200000

300000

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600000

-5 -4 -3 -2 -1 0 1 2 3 4 5

Inclination (deg)

Acc

umul

ated

leng

th (m

)

grouping by inclination classes

Lumping by inclinations inascending order

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200

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600

800

1000

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1400

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2000

30 35 40 45 50 55 60 65 70

Export flow rate [MSm3/d]

Con

dens

ate

cont

ent [

m3]

Original profile 20-70 km'lumping by inclination in ascending order'

'Sorted by inclination classes'


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Step 4)Redistribution of elements by “Simulated Annealing” (Travelling salesman problem)“minimize distance between detailed profile and simplified profile”

yi : values from the simplified profile

ŷi : values from the detailed profile

wi : weight factor

where as “i” denotes:

1) Elevation

2) “Total Climb”

3) “Pipeline Indicator” *

2)()( ii ii yywyF −⋅=∑Cost function:

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0

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Distance (m)

Elev

atio

n (m

)

-400-350-300-250-200-150-100-50

0

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Distance (m)

Ele

vatio

n (m

)

-300-290-280-270-260-250-240-230

70000 75000 80000 85000 90000 95000 100000

Distance (m)

Elev

atio

n (m

)


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Original profile

Simplifiedprofile

Method 1profile

Method 2profile

Number of pipes 108,784 554 2,766 2,550Pipeline profile indicator 79.7 25.8 80.3 80.3Total climb [m] 4,187 1,235 4,180 4,187Total length [m] 554,505 554,400 554,507 554,505

Comparison

Pipeline geometry

-300-290-280-270-260-250-240-230

70000 75000 80000 85000 90000 95000 100000


Elev

atio

n [m

]

Original profileSimplified profileDiscretized profile (method 1)Discretized profile (method 2)


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Angle distributionsPipe angle distribution

0

10000

20000

30000

40000

50000

60000

70000

80000

(-90,

-60)(-3

0, -20)

(-10,

-5)(-2

, -1)

(-0.5,

-0.25

)(0,

0.01

)(0.

1, 0.2)

(0.3, 0

.4)(0.

5, 0.75

)(1,

1.25

)(1.

5, 2)

(2.5, 3

)(4,

5)(6,

7)(8,

9)(10

, 20)

(30, 9

0)

Pipe angle group [deg]

Tota

l pip

e le

ngth

per

ang

le g

roup

[m]

Original profileDiscretized profile (Method 2)Discretized profile (Method 1)Simplified profile


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Steady-state simulation: original vs. discretizationCondensate content vs. export flow rate

42" ND pipeline - Fluid: 50%J0/50%J1 - OLGA steady-state pre-processor

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1000

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1400

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30 35 40 45 50 55 60 65 70Export flow rate [MSm3/d]

Con

dens

ate

cont

ent [

m3]

Original profile 20-70 km

Discretized profile 20-70 km (Method 1)

Discretized profile 20-70 km (Method 2)


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Steady-state simulation: simplified vs. discretizationTotal condensate content vs. export flow rate

42" ND pipeline - Fluid: 50%J0/50%J1 - OLGA steady-state pre-processor

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

20 25 30 35 40 45 50 55 60 65 70

Export flow rate [MSm3/d]

Tota

l con

dens

ate

cont

ent [

m3]

80

100

120

140

160

180

200

Inlet pressure [bara]

Total condensate content (simplified profile)Total condensate content (method 1)Total condensate content (method 2)Inlet pressure (simplified profile)Inlet pressure (method 1)Inlet pressure (method 2)


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Conclusions• Simplification of long and rough gas-condensate pipeline profiles is a key issue for correct design

• Two methods were introduced for the development of the Shtokman field – Phase 1

• Essential characteristics of the original detailed pipeline profile are conserved:

Length + Topography + Angle distribution + Total climb

• The hydrodynamic behavior of the original profile is conserved through both methods despite significant data compression

bhrg 2009 no_backup

Documents

total pipe length

detailed pipeline profile

discretized profile

total length

average pipe length

pipe inclination0

id length

small pipe sections