Discretisation, characterisation, and complexification of multiphase pipeline elevation profiles

1. www.bhrgroup.co.uk
16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Discretisation, characterisation,
and complexification of multiphase
pipeline elevation profiles

2. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Contents
• Context
• Profile discretisation
• Method (MPT 2009, Cannes)
• Recommendations and lessons learnt
• Profile characterisation
• Roughness indicators and regression
• Profile complexification
• Method and example
• Conclusions

3. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Context
• Bathymetric / hypsometric data for the concept
select phase of field developments are usually scarce
• Detailed profile data from geophysical surveys or
pipeline inspection may be available later
‐100
‐50
0
0 50 100 150 200 250
Elevation [m]
Distance [km]
Detailed profile Early profile

4. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Liquid holdup vs. pipe angle (gas transport)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
‐5 ‐4 ‐3 ‐2 ‐1 0 1 2 3 4 5 6 7 8 9 10
Condensate holdup [‐]
Pipe inclination [deg]
Dry gas‐condensate
Condensate holdup vs. pipe inclination
and gas superficial velocity (Usg)
Usg=1.05 m/s Usg=1.58 m/s Usg=2.12 m/s
Usg=2.65 m/s Usg=3.19 m/s Usg=3.73 m/s
Usg=4.27 m/s Usg=4.81 m/s Usg=5.35 m/s
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
‐5 ‐4 ‐3 ‐2 ‐1 0 1 2 3 4 5 6 7 8 9 10Total liquid holdup [‐]
Pipe inclination [deg]
Wet gas‐condensate
Total liquid holdup vs. pipe inclination
and gas superficial velocity (Usg)
Usg=1.06 m/s Usg=1.60 m/s Usg=2.14 m/s
Usg=2.67 m/s Usg=3.22 m/s Usg=3.76 m/s
Usg=4.30 m/s Usg=4.83 m/s Usg=5.34 m/s

5. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Water holdup vs. pipe angle (oil transport)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
‐5 ‐4 ‐3 ‐2 ‐1 0 1 2 3 4 5 6 7 8 9 10
Water holdup [‐]
Pipe inclination [deg]
Oil & water
Water holdup vs. pipe inclination
and oil superficial velocity (Uso)
Uso=0.07 m/s Uso=0.10 m/s Uso=0.13 m/s
Uso=0.20 m/s Uso=0.27 m/s Uso=0.40 m/s
Uso=0.67 m/s Uso=0.93 m/s Uso=2.00 m/s
0
0.1
0.2
0.3
0.4
0.5
0.6
‐5 ‐4 ‐3 ‐2 ‐1 0 1 2 3 4 5 6 7 8 9 10Water holdup [‐]
Pipe inclination [deg]
Oil, water & gas
Water liquid holdup vs. pipe inclination
and oil superficial velocity (Uso)
Uso=0.25 m/s Uso=0.41 m/s Uso=0.58 m/s
Uso=0.75 m/s Uso=0.91 m/s Uso=1.08 m/s
Uso=1.24 m/s Uso=1.41 m/s Uso=2.08 m/s

6. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Methodology
• Complexification of scarce elevation contours is
recommended to model the influence of the terrain
roughness on the hydrodynamic behaviour of multiphase
flows
• Simplification of detailed bottom-of-pipe and terrain
profiles is necessary
• to produce suitable profiles for the dynamic simulation
of multiphase flows
• while preserving the hydrodynamic behaviour of the
original (detailed) profile  Discretisation

7. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Profile discretisation: minimum requirements
1. Both horizontal span and length should be preserved
2. The angle distribution of the discretised profile should
be as close as possible to the original distribution
3. The Total Climb (sum of uphill flow elevation changes)
should be conserved
Original profile
2
1
3

8. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Additional requirements for dynamic simulation
1. The overall shape (large and small scale undulations)
should be preserved
2. The distribution of segment lengths should be as
uniform as possible
1
2
Original profile

9. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Discretisation method (MPT 2009, Cannes)
1. Select data points from the original profile
2. Add intermediate segments
3. Change the elevation of intermediate segments
randomly to match the original Profile Indicator and
Total Climb
‐120
‐119
‐118
‐117
‐116
48,000 48,500 49,000 49,500 50,000
Elevation [m]
Distance [m]
Original profile
Discretised profile
Simplified profile

10. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Profile Indicator and Total Climb
0
0.1
0.2
0.3
0.4
0.5
‐5 0 5 10Holdup [‐]
Pipe angle [% or deg]
[%]
[deg]
= segment angle in %
= segment length
= segment elevation change
= total number of segments

11. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Recommendations
• The resolution of the original profile should (ideally) be
about 3 metres and should not exceed 50 m or so
• Scarce and steep sub-profiles must be removed from the
original profile
• Detailed portions can be used to generate roughness
indicators for scarce sub-profile data
• Rough simplification of vertical or steep geometries may be
required to avoid severe time step limitation during dynamic
simulation
• Any noise in the profile data must be filtered to remove
any unphysical roughness

12. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Lessons learnt
• Step 1: Can the discretisation of pipeline profiles be
limited to a selection of original points?
• Yes if the Terrain Indicator profile is close to zero
• Step 2: four (4) intermediate segments are adequate in
most cases for complexification
• Step 3: complexification can be run on uniform
distributions of sub-profiles
• A constant 10 km span (or so) is adequate in most cases
• Lumping of sub-profiles is not necessary

13. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
• The relative difference between original and
discretised Total Climbs shall not exceed 1%
• A larger deviation is acceptable for the Profile Indicator
• but a difference < 1% is feasible in most cases
• An increase in the number of original points in Step 1 is
the best method to improve the angle distribution fidelity
and capture original terrain undulations
Lessons learnt

14. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
‐600
‐400
‐200
0 10 20 30 40
Elevation [m]
Distance [km]
Two pipeline profiles with a Total Climb of 400 m
Characterisation and complexification
• The Profile Indicator and Total Climb are two practical
indicators to quantify the propensity of a pipeline for
accumulating liquids
• However both combine small scale features (terrain
roughness) and large scale undulations (overall profile)
Rugged seabed (PI = 88)

15. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Roughness indicators
‐140
‐130
‐120
0 5,000 10,000
Elevation [m]
Distance [m]
Original bottom‐of‐pipe profile Smooth profile
x
z

16. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Region-specific regressions
y = 0.1546x ‐ 4.2183
0
4
8
12
16
20 40 60 80 100 120
Terrain Indicator [‐]
Rough Profile Indicator [‐]
Barents Sea
Pipeline A Pipeline B
y = 0.0652x + 0.1076
0
1
2
3
0 10 20 30 40 50
Terrain Indicator [‐]
Rough Profile Indicator [‐]
Persian Gulf
Pipeline A Pipeline B Pipeline C

17. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Region-specific regressions
y = 0.0848x ‐ 0.3796
0
1
2
3
4
5
6
7
8
9
0 20 40 60 80 100
Terrain Indicator [‐]
Rough Profile Indicator [‐]
North Sea
Pipeline A Pipeline B Pipeline C
y = 0.0739x + 0.1084
0
1
2
3
4
5
0 10 20 30 40 50 60
Terrain Indicator [‐]
Rough Profile Indicator [‐]
North West Shelf
Pipeline A Pipeline B

18. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Region-specific regressions
y = 0.0896x ‐ 0.2207
0
2
4
6
8
10
12
0 20 40 60 80 100
Terrain Indicator [‐]
Rough Profile Indicator [‐]
Timor Sea
Pipeline A Pipeline B

19. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Seabed profile vs. bottom-of-pipe profile
0
2
4
6
8
0 20 40 60 80 100
Terrain Indicator [‐]
Rough Profile Indicator [‐]
North West Shelf Pipeline A
Seabed Bottom‐of‐pipe (normal op. conditions)

20. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
0
2
4
6
0 10 20 30 40 50 60
Terrain Indicator [‐]
Rough Profile Indicator [‐]
North West Shelf Pipeline A
Bottom‐of‐Pipe (normal op. conditions)
Seabed features
Rugged terrain
(scarps, ridges)
Benign features
(megaripples, sandwaves)

21. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Complexification method: example
y = 0.0739x + 0.1084
0
1
2
3
4
5
0 10 20 30 40 50 60
Terrain Indicator [‐]
Rough Profile Indicator [‐]
North West Shelf
Pipeline A Pipeline B
‐120
‐100
‐80
‐60
‐40
‐20
0
0 100 200 300Elevation [m]
Distance [km]
Dummy pipeline
elevation profile
RPI = 50
RPI = 10
Original Profile

22. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Complexification method
1. Split each straight sub-profile into segments of same
distance (e.g. 1 km)
2. Add intermediate segments
3. Change the elevation of intermediate segments
randomly to match the Total Climb (and Profile
Indicator) calculated from the regression between the
Terrain Indicator and Rough Profile Indicator

23. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Angle distribution and indicators
Original profile
(RPI = 0)
RPI = 10 RPI = 50
Profile indicator [-] 3.8 11.5 58.7
Total climb [m] 100 363 1,282
0
50,000
100,000
150,000
200,000
250,000
Total pipe length per
angle group [m]
Pipe angle group [deg]
RPI = 50
RPI = 10
Original profile (RPI = 0)

24. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Dry gas-condensate flow: simulation results
0
5,000
10,000
15,000
20,000
0 20 40
Condy accumulation [m3]
Total mass flow rate [kg/s]
Dry gas‐condensate flow
Condy accumulation vs. mass flow rate
RPI = 50
RPI = 10
Original profile
0
20
40
60
80
100
0 20 40
Pressure drop [bar] Total mass flow rate [kg/s]
Dry gas‐condensate flow
Pressure drop vs. mass flow rate
RPI = 50
RPI = 10
Original profile

25. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Wet-gas condensate flow: simulation results
0
5,000
10,000
15,000
20,000
0 20 40 60 80 100
Liquid accumulation [m3]
Total mass flow rate [kg/s]
Wet gas‐condensate flow
Liquid accumulation vs. mass flow rate
RPI = 50
RPI = 10
Original profile
0
40
80
120
0 20 40 60 80 100
Pressure drop [bar] Total mass flow rate [kg/s]
Wet gas‐condensate flow
Pressure drop vs. mass flow rate
RPI = 50
RPI = 10
Original profile

26. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Two-phase oil-water flow: simulation results
0
5,000
10,000
15,000
20,000
25,000
30,000
0 50 100 150 200
Water accumulation [m3]
Total mass flow rate [kg/s]
Two‐phase oil‐water flow
Water accumulation vs. mass flow rate
RPI = 50
RPI = 10
Original profile
0
20
40
60
80
100
0 50 100 150 200
Pressure drop [bar] Total mass flow rate [kg/s]
Two‐phase oil‐water flow
Pressure drop vs. mass flow rate
RPI = 50
RPI = 10
Original profile

27. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
3-phase oil-water-gas flow: simulation results
0
50
100
150
0 50 100 150 200
Pressure drop [bar] Total mass flow rate [kg/s]
Three‐phase oil‐water‐gas flow
Pressure drop vs. mass flow rate
RPI = 50
RPI = 10
Original profile
20,000
25,000
30,000
35,000
40,000
0 100 200
Water accumulation [m3]
Total mass flow rate [kg/s]
Three‐phase oil‐water‐gas flow
Water accumulation vs. mass flow rate
RPI = 50
RPI = 10
Original profile

28. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Conclusions
• Region-specific regressions between roughness
indicators can be used to generate representative,
complexified profiles when detailed seabed data are not
available
• Non-dimensional indicators can be used to:
• Quantify the roughness of pipeline elevation profiles
• Model the smoothing effect of pipeline laying on the seabed
profile (using reduced roughness indicators)
• Anticipate the severity of hydrodynamic phenomena such
as liquid build-up for various pipeline routes
• Improve the interpretation of multiphase flow simulations

29. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Discretisation, characterisation, and
complexification of multiphase pipeline
elevation profiles
Erich Zakarian & Julie Morgan
Woodside Energy Ltd, Australia
erich.zakarian@woodside.com.au
julie.morgan1@woodside.com.au
Henning Holm
Statoil, Norway
hthol@statoil.com
Dominique Larrey
Total, France
dominique.larrey@total.com

30. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Back-up slides

31. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Smooth Profile Indicator (SPI)
‐100
‐50
0
50
100
150
200
250
300
350
400
‐10 ‐5 0 5 10
Smooth Profile Indicator [‐]
Sub‐profile inclination [deg or %]
Smooth profile indicator (SPI) vs. sub‐profile inclination
SPI vs. inclination [deg] SPI vs. inclination [%]

32. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Rough Profile Indicator (RPI)
‐250
‐200
‐150
‐100
‐50
0
50
100
150
200
250
‐100
‐50
0
50
100
150
200
250
300
350
400
‐10 ‐5 0 5 10
Rough Profile Indicator [‐]
Profile Indicator [‐]
Sub‐profile inclination [deg]
PI and RPI vs. sub‐profile inclination
Profile Indicator (PI) [‐] Rough Profile Indicator (RPI) [‐]
Terrain Indicator [‐] = 10

33. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Pipeline profile database: TI vs. RPI
0
2
4
6
8
10
12
0 20 40 60 80
Terrain Indicator [‐]
Rough Profile Indicator [‐]
Timor Sea Persian Gulf North West Shelf North Sea

34. 16th International Conference on Multiphase Production Technology
Cannes, France 12 – 14 June 2013
Pipeline profile database: TI vs. RPI
0
2
4
6
8
10
12
14
16
18
0 20 40 60 80 100 120
Terrain Indicator [‐]
Rough Profile Indicator [‐]
Timor Sea Persian Gulf North West Shelf North Sea Barents Sea