OLGAS - re l iabi l i ty for mult iphase f low

OLGAS is the steady state flow correlation based on OLGA®

- the industry standard for dynamic multiphase flow

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OLGAS

Using the OLGA® model for steady state calculationsOLGAS is a mechanistic point model that calculates pressure gradients, liquid hold-up and flow pattern at a specific section of pipe/tubing.

OLGAS is available in both the 2- and 3-phase options.

Being a reference model with superior predictive capabilities, OLGAS is the natural default flow model in all steady state applica-tions.

Why OLGAS?OLGAS is the superior mechanistic model that has been

developed from laboratory and test data supplied

by operating companies since the mid 80’s. OLGAS

is continuously being developed in conjunction with

the OLGA® dynamic simulator and the power in the

development has never been stronger than today.

OLGAS updates are typically released twice per year.

The correlation challengeEngineers are charged with the responsibility to find

the appropriate multiphase correlation for systems

- especially when:

Lack of appropriate data when a new well or

pipeline is being designed.

“Industry Standard” correlations do not fit the

available test data for some or all of my wells.

Different correlations are used to match similar

wells.

The same correlation yield incomparable results in

different application.

OLGAS is developed to support the engineer in these

situations. No other flow model is valid in a wider

operation than OLGAS.

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The OLGAS codeThe OLGAS program is a steady-state multiphase model for

the calculation of pressure drop, local phase volume frac-

tions and related information at a single point in a pipeline.

The OLGAS point model is available as a FLEXlm protected

dll, which may be dynamically linked to (e.g.) a steady-state

pipeline/well flow simulator.

The OLGAS dll has three main interfaces defined:

2 phase interface

3 phase interface

3 phase interface w/effective oil and water phase vis-

cosity including water/oil dispersion effects

There are also defined interfaces for license control, extended

input and output:

The OLGAS DLL is currently available on the Winnt, Win32 and

Linux. Default programming languages available for interfac-

ing is Fortran 77/90/95 and C/C++.

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OVIP – a key driver in the OLGAS developmentOVIP (OLGA® Verification an Improvement Project) is a

multi-client joint industry research and development

program for validation and improvement of OLGA®. Over

the last decade a chain of OVIP projects have dramatically

improved the performance of the point model OLGAS. The

current OVIP program is supported by BP, Chevron, ENI,

ExxonMobil, Petrobras, Statoil, Total and Shell.

OVIP embodies by far the largest multi-

phase flow data collection ever assembled.

Containing both experimental and field data,

including gas/condenasate pipelines, lower

GOR pipeline, well, and transient data, OVIP

contributes to significant improvements in

OLGA® and OLGAS.

Some of the recent improvements includes

important phenomena in stratified flow:

Wall shear stress models

Droplet entrainment models

Gas entrainment in the liquid layer

Droplet deposition on the pipe wall

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3rd Party AvailabilityEach 3rd-party supplier is afforded identical implementations of OLGAS to assure that the flow correlation results provided by one simulator will be comparable to those from another. Vendors typically offer bi-annual upgrades.

OLGAS is available, with a product specific license, from a number of leading vendors of steady state simulators:

Aspentech - Hysys®

Calsep – DepoWax®

Honeywell - UniSim®

Invensys - PIPEPHASE®

Neotech - Wellflo® & Pipeflo®

Petroleum Experts - Prosper® & GAP®

Schlumberger - PIPESIM® familyand others

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OVIP – with focus on wellsWork on multiphase flow in vertical upward wells and risers

shows that there are fundamental differences between the

flow in small and large diameter pipes. In flow patterns occur-

ring in vertical upward flow the relative importance of flow

regimes is very different for small and large pipes. In the OVIP

2002-03 project, OLGA was modified to take this better into

account. Also, a new correlation for entrainment in annular

flow by Pan & Hanratty (2003) has been modified based on

the unique high-pressure data from the

SINTEF Multiphase Flow Laboratory. These

enhancements have improved OLGAS pre-

dictions of pressure drop in vertical annular

flow in wells and risers.

Experiments in the Well Loop at the Institute for Energy Technology (IFE)

Selected References • Nossen, J., Shea, R.H., and Rasmussen, J.: New

developments in flow modelling and field data

verification: Banff 2000.

• Bendiksen, K., Malnes, D., Moe, R. & Nuland, S.:

The Dynamic Two-Fluid Model OLGA: Theory

and Application. SPE Production Engineering,

May 1991, pp. 171-180

• Shea, R., Rasmussen, J., Hedne, P. and Malnes,

D.: Holdup predictions for wetgas pipelines

compared. Oil & Gas Journal, May 19, 1997

OLGAS vs Beggs & Brill 7.5” ID 1deg incl

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www.olgaworld.com olga@sptgroup.com

SPT Group is the world leader in dynamic modelling

for the oil and gas industry. Employing highly

skilled professionals worldwide, SPT Group

provides a combination of software and

consulting services within multiphase

flow and reservoir engineering.

www.sptgroup.com

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