OLGA6 Tips & Tricks

8/19/2019 OLGA6 Tips & Tricks

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OLGA User Group Meeting

OLGA SupportTips & TricksBeijing, UGM, Oct. 18, 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

http://www.sptgroup.com/http://www.sptgroup.com/


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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 maximumperformance with OLGA ?

3. Is OLGA compatible with Windows 7 ?

4. Can OLGA simulate Water Hammer effects ?5. Why does not always the 2 nd 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 betweenOLGA 6 and OLGA 5 ?


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What is NOT different inOLGA 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 theSPT 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 lowflow rates

• better consistency between steady state pre-processor anddynamic 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 givesignificant performance boost when run on such systems

• Most benefit for –

large cases with few nodes, long pipelines and a relativesmall amount of process equipment


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What hardware is recommended to achievemaximum 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)

N o r m a

l i z e

d w a

l l c

l o c

k t i m e

Cores+Hyperthreading

Oil field Gas-condensate

Running 2 CPUs onsame machine

Running 2 threads oneach 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

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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/m 3)

• Maximum hammer pressure achieved if valve closure time is

shorter than system response time:

L = pipeline length

l l vc P max

c

Lt

r

2


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• Fluid packingcontributes topressure increase

• Small spatialdiscretizationgives betterresolution ofpressure wave

4 km long pipeline with flowing water


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• Elastic walls

• more correctvolume change &speed of sound

4 km long pipeline with flowing water


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Why does not always the 2 nd order numericalscheme give more accurate results?


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2nd Order Scheme for Mass Equations

• It should be used for cases with holdup or concentrationgradients e.g.

– Start-up – Rate change –

Slugging – Injection of inhibitors

• 2nd order scheme is not recommended for simulations whereinstabilities 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 feedbackfrom users


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be dynamic

Documents

OLGA6 Tips & Tricks