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INFORMATION FOR

BEGINNING WITH OLGA

Plan of this page :

1. Presentation of Olga ScandpowerSoftware

2. First steps with Olga

3. Some advises about the GUI

4. Some advises about the PVT file

5. General advises

Presentation of Olga Scandpower Software

Olga is a Norwegian petroleum software originally developed by IFE for Statoil in 1983. Olga2000 is capable of one dimensional simulation of Oil, gas and water flows. You can find

information about the Olga model in The dynamic Two-Fluid Model Olga: Theory andapplicationby Bendiksen, K.H Malnes, D. Moe, R. and S. Nuland edited by SPE ProductionEngineering, May 1991, pp. 171-180.

Olga is supposed to can be used for:

Oil and Natural gas flowlines or transportation lines, Wet gas or condensate pipelines, Well stream from a reservoir, LNG / LPG/ NLG pipelines, Dense phase pipelines, Network of merging pipelines, Artificial lift and other mass source injections, Pipelines with process equipment ( compressor, heat exchanger, separators, check-valve,

controller, mass source / sink),

Single phase gas or liquid, Small diameter pipelines with various fluids, Laboratory experiments.
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The input system of Olga consists in six files. Input file 1 & 2 are always required while 3,4,5 &

6 are optional.

File 1 (name.inp): General case definition: name, reference, geometry, operational conditions,

output variables

File 2 (name.tab): Fluids properties definition ( also called PVT file )Files 3, 4, 5 & 6: Optional files for compressor, pump & restart file.

The version I used is an Olga Graphic User Interface (GUI) version called Olga 2000.

The GUI allows the user to :

create the files 1, 3, 4, 5 & 6 directly via several modules (keywords), draw graphs, verify the TXV file (Fluid Properties button),

In a nutshell, the GUI simplifies considerably the using of Olga in defining the case in some

windows and not in a text editor. Besides, even if you have an Olga GUI version, you cancomplete directly the files in a text editor of your choice (it also allow the user to control what he

enters in the interface). Moreover, the GUI propose you two ways of launching the calculus : abatch version or a interactive version (in which you can reduce the time of your simulation

without changing the file).

First steps with Olga

How getting helpTo found help, refer to the two written manuals of Olga 2000 ( User's Manual for global

information about Olga & Getting Started for the GUI using) or click on help directly underOlga, then you will access to the HTML version of User's Manual.

You can also contact directly Scandpower.

How beginningTo begin with Olga, I recommend you look the Olga examples (at the end of the User's Manual,

appendix C to O). Personally, I used the first example (appendix C) to understand how to

implement the Olga files. First, I opened this case and saw how to draw graphs. Then, I openedthe different modules of the GUI version of the case main file (click on 'show Keyword' to have

a direct access to these modules) . And then, I tried to reproduced the same case under the Olga

GUI. In that way, I understood how to enter the case and when I encountered problems, I opened

the .inp file (case file) to see really what I had entered.In that way, I understood how to select an item in a list, how to enter different values in a same

line (as example, different times), how to draw graphs and how to access to the modules I want

to implement.


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Then to implement networks of pipes, I used the second example (appendix D).

In the following section, I give some advises relative to the major problems I encountered.

Some advises about the Olga GUI

The Graphic User Interface of Olga is quite simple to take into hands but I encountered some

difficulties to enter some values in the different modules.

ClickHEREto see the GUI

Thanks to the GUI, you can directly:

Launch the calculus, Create the case files (but not the PVT), Draw graphs (Trend or Profile).

Following some advises about problems I encountered.

Founding the divers modules of the files

To use correctly the Olga GUI, you have to press the 'keywords' button. In that way, all the basicmodules you have to complete would appear. For the other modules, you can enter into a

modules and press next until the desired module appears or (better) directly select the desire

module via the upper tools bar, section Keywords .

Entering divers values in a same lineIt is simple but I encountered some difficulties the first time I went to enter different time values.

As example, I want to enter a mass flux time dependant. I enter three time values: at t = 0 s, t =20.5 s and t = 40 s. I have to enter in the time line : 0.0 , 20.5 , 40 (without the parentheses, but

they will be added in the text version of the file). For the other lines of the module, you have to

enter 3 values of the property corresponding to the different times (always without parentheses).

Remark: If Olga does not agree with your values, they will disappear instantaneously with a

'bip'.

Selecting an item in a list (as example the pipe or branch ...)

This is also simple but the first time it can be problematic. In fact, you cannot directly enter thename of your item, you have to select it on a list.

When you have to select an item in a list, a special button is put at the end of the line. It is arectangular button with three points or with a arrow pointing down. Press this button to obtain

the list. Then select the item and click on replace (if this button appears).

Avoiding the GUISometimes, the GUI refuses a value (this value disappear and you can hear a 'bip').
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It can be because your value is not correct: you have entered divers time values so you have to

enter a list for this line. If you think to have right, do not hesitate to open the .inp file in a text

editor. In that way, you can verify your case and change what you want.

ClickHERE to see the GUI

Some advises about the PVT file

In this file, the divers properties of the fluids are defined.

There is a tool to help the user to create this file but I do not have it at my disposal. So I createdmy own PVT file directly in a text editor. To have a referenced, I opened an Olga PVT file

example (Ol-terslug-1.tab) and with the manual, I changed it to adapt it to my case.

Consequently, if you have to do the same or to read such a file I can give you some advises

relative to my case.

In the first line, between quota, a code is written to identify the fluids. In the second line, enter the number of, respectively, pressure and temperature steps you

want to define:

NbP NbT

In the third line, enter respectively the pressure and temperature steps (in bar and degreeCelsius):

DeltaP DeltaT

In the fourth line, enter the 'initial' point: initial pressure (in bar) and initial temperature(in degree Celcius)

Po To

In that way, you will defined the properties of your fluids in NbP * NbT points:

P between Po and Po + deltaP * (NbP 1)

T between To and To + deltaT * (NbT 1)

In the fifth and sixth lines, enter NbT numbers. Personally, I do not know what theyrepresent and I let the numbers I found in the Olga example.

Then, you will have to write a keyword representing a property of the liquid or gaseousphase. Below this keyword, you will have to give the value of this property at eachpoints. You will write NbP lines of NbT values. You can consider that as a matrix. In the
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line i and column j, you will write the value at Po + deltaP * (i - 1) bar and To + deltaT *

(j - 1) degree celcius.

Two other advises :

If you go to the help section of your manual about the second file (name.tab), you willsee that some keywords do not correspond to the manual. In fact, in this file, as example,

the evolution of the the volumic mass of the gas function of the temperature isrepresented by the keyword drogdt.

Generally, you can assume that the gaseous phase is perfect and its density verifies thefollowing equation:

General Advises

Incomprehensible error message

Olga functions under Windows and both are unstable. Consequently, do not hesitate to closeyour case and reopen it to launch it if you have an error stating that you have no license or that

the application is busy. Besides, if you close the Olga deamon then you have to reopen it to

launch simulation in the Execution control mode.

DebuggingTo debug your case, you can use the batch execution mode (run batch): it would write step by

step the errors it encountered in your files. In that mode you can also launch the debugger ofOlga (it will underline the non physical aspect of your case), you have only to select 'on' in the

case OPTIONS module in front of DEBUG (keyword = ' OPTIONS').

Be simple at the beginningPersonally, at the beginning, I only used the examples 1 and 2 of the Olga manual. With these

examples, I simulated a vertical pipe and a network of pipes with one manifold for four wells. Ionly used sources to introduce flows. I introduce a valve but without checkvalve. In fact, I only

create and use the principal files of Olga but not the equipment files.

Simulation of a steady statePersonally, I simulated steady state via launching the simulation for 20 or 5 seconds. In that way,

the calculus converged to the steady state.

Flows entry conditionsWith Olga, you have to enter the total mass flow rate (Qt) and the gas fraction (Gfraction).

These quantities can be understand via the following formulas:


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J is the surface velocity, Q the mass flow rate, S the surface of the section and rho the density.

The values keywords

To edit value (via Trend, Profile or Output modules), you have to define them with theirkeywords. As example :

to edit the flow regime indicator, use ID, to access to the void fraction, write AL, to edit jg (the gas velocity or gas flux), enter USG, to edit the pressure, enter PT...

All these keywords are given at the end of the Olga principal manual.

The output fileYou can visualize your results directly with the GUI (Trend or Profile sections) but you can also

write the results in a text file with a .out extension. You can open this file in a text editor ( like

Wordpad ). You can use the Output section of the .inp file to determine the values you want towrite (with the keyword given in annexes). In the .out file, you will read the .inp file and the

output results you have implemented in the Output section. You can also open this file with

Excel and draw your own graphs. It is very interesting to open this file because you will discoverwhat is really implemented in your case (in particular, you will see that some values are taken in

the center of the cells and some other in the limits of the cells).

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