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OLGA User Group Meeting OLGA Support Tips & Tricks Johan Henriksson Aberdeen, November 10 th 2010

TIP & TRAP

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Page 1: TIP & TRAP

OLGA User Group Meeting

OLGA Support Tips & Tricks

Johan Henriksson

Aberdeen, November 10th 2010

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OLGA support

• Send to [email protected]

• Support Center – access to FAQ, track your support requests

• Requesting user feedback on support

• Check www.sptgroup.com for new minor releases

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Feedback from earlier UGMs

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Tips & Tricks

1. What is the main difference between OLGA 6 and OLGA 5 ?

2. What hardware is recommended to achieve maximum

performance with OLGA ?

3. Is OLGA compatible with Windows 7 ?

4. Can OLGA simulate Water Hammer effects ?

5. Why does not always the 2nd order numerical scheme give

more accurate results?

6. Why is AXIALHEAT not included in OLGA 6?

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What is the main difference between

OLGA 6 and OLGA 5 ?

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What is NOT different in

OLGA 6 compared to OLGA 5 ?

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OLGA 6 and OLGA 5 : same concept

• fundamental modeling concept is the same

– Flow model

– Numerical methods for conservation equations

• Graphical User Interface (GUI) is the same

• Comparisons from cases in OVIP data base and from the

SPT functional test repository show that:

OLGA 5 and OLGA 6 will in general give very similar results

both for steady-state and transient simulations

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Conservation equations in OLGA 6

• three momentum equations (gas, oil, water)

– effect when individual momentum of oil and water are

important (heavy slugging in risers)

• an interfacial level gradient term between oil and water

– give higher water content in gas condensate pipelines for low

flow rates

• better consistency between steady state pre-processor and

dynamic solution

– interfacial level gradients included in pre-processor

• 2nd order scheme for mass equations

– optional

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OLGA 6 has a new node model

• Internal nodes have a finite volume

– use same physical and numerical models as sections

– more general than split/merge => easier to model closed loops

• No momentum transfer across nodes

– higher pressure drop for cases with high velocity

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Process equipment in OLGA 6

• Controllers are signal network components

– Coupled in the controller signal network

• Separator is a flow network component

– Similar to multi-train separator in OLGA 5

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The OLGA 6 code is parallelized

• developed for multi core platforms, and may give

significant performance boost when run on such systems

• Most benefit for

– large cases with few nodes, long pipelines and a relative

small amount of process equipment

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What hardware is recommended to achieve

maximum performance with OLGA ?

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Effect of several cores and CPU’s

Tested using 2 Quad core Intel CPUs with Hyperthreading

(2 threads per core)

Speedup is case dependent

0

0.2

0.4

0.6

0.8

1

1.2

1 2 3 4 4+4 2*(4+4)

No

rma

lize

d w

all

clo

ck

tim

e

Cores+Hyperthreading

Oil field Gas-condensate

Running 2 CPUs on

same machine

Running 2 threads on

each core

(Hyperthreading)

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What CPU to buy?

• Speedup is dependent on e.g.

– Size of problem

– Dominating flow regime

– Modules used

• True multicores give good speedup

• Good effect of Hyperthreading (Intel)

• Effect of multi-CPU for larger problems

• AMD and Intel Quad core give good speedup

• Expects good performance on new 6 and 8 cores CPUs

14

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Is OLGA compatible with Windows 7 ?

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Windows 7 compatibility

• Yes, with some known exceptions

• OLGA is not supported on

– PCs with Windows 7 + integrated Intel graphic card and

integrated Intel driver

• Following issues happen more often on Windows 7

– ‘Copy as picture’ of the network view to clipboard fails

– Input report does not include image of the network view

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Can OLGA simulate Water Hammer effects?

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Water Hammer simulations in OLGA

• Hammer effects occur in liquid systems with fast transients

– Injection systems

• Maximum hammer pressure :

P = Pressure (Pa)

c = Wave propagation velocity (speed of sound) (m/s)

v = Fluid flowing velocity (m/s)

ρ = Density (kg/m3)

• Maximum hammer pressure achieved if valve closure time is shorter than system response time:

L = pipeline length

ll vcP max

c

Ltr

2

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Water Hammer simulations in OLGA

• Fluid packing

contributes to

pressure increase

• Small spatial

discretization

gives better

resolution of

pressure wave

4 km long pipeline with flowing water

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Water Hammer simulations in OLGA

• Elastic walls

• more correct

volume change &

speed of sound

4 km long pipeline with flowing water

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Theoretical comparisons

• Instantaneous closing valve, Joukowski equation:

• For slower occurring changes the following relationship is

used to estimate the surge pressure:

Comparison between OLGA,

Joukowski equation and

slow-close-equation

0

5

10

15

20

25

30

35

40

45

50

0 10 20 30 40 50

Ha

mm

er

pre

ssu

re (

bar)

Valve closing time (s)

OLGA

Slow close

Joukowski

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Water Hammer simulations in OLGA

• Advice for simulation hammers in OLGA

– Spatial discretization is important

– Use DTCONTROL : SOUND_CFL = ON

small fixed time steps (dt = 2Ls/c)

– Account for elastic walls with ELASTIC = ON

• CONCLUSION

– OLGA can simulate water hammer effects

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Why does not always the 2nd order numerical

scheme give more accurate results?

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2nd Order Scheme for Mass Equations

• It should be used for cases with holdup or concentration

gradients e.g.

– Start-up

– Rate change

– Slugging

– Injection of inhibitors

• 2nd order scheme is not recommended for simulations where

instabilities are observed

• enhances the numerical oscillations

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Why is AXIALHEAT not included in OLGA 6?

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AXIALHEAT

• Not implemented in OLGA 6 yet because

– Model in OLGA 5 is sensitive to pipeline geometry

– Should only be used for vertical risers

– No field data is available

• May be included in later versions depending on feedback

from users

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be dynamic