Tuning EOS parameters

[hoanglongbk88]

I am learning to calibrate cubic EOS for compositional simulation. Who can share me some experience to match between PVT of gas condensate calculated from EOS and observations by using PVTi in ECLIPSE solfware. How to quality check the PVT model after matching?
I am appriciated with your all kind help.

[munqith]

which cubic EOS's are you used?

[hoanglongbk88]

I use Peng-Robinson three parameters and volume shift is independent on critical properties.

[Shakespear]

hoanglongbk88
Check the tutorials for PVTi by opening the PVTi manual.

Also there is a PVT course by Whitson on egpet that may also help.

[hoanglongbk88]

I have read the PVTi manual , but I cannot match the PVT of gas condensate.

[Shakespear]

I have read the PVTi manual

But did you do the Tutorials that are in that manual?
None of this tuning work is easy and I think it very difficult to explain it through emails. That is why a course is the best way to go. However the tutorials are good way to go because they go step-by-step to show you the procedure.

The Whitson videos were the best that I have seen on the net regarding PVT analysis. However even in this case the problems they did were not available hence you only get half of the knowledge.

Look here and see if some useful info may be located

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Whitson's lecture stressed what is in this paper

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and he made it know that he thought that his program did a better job of controlling the tuning process than PVTi. You would need to listen to the lecture to try and understand this.

Also you would need to do a validation of your pVT data else your tuning will go nowhere.

[link Point to another website Only the registered members can access]

[hoanglongbk88]

I know that it is very difficult to tune the EOS parameters. I read the tutorial of PVTi. As you see there are a lot of combinations of regression variables. I tried to do step by step as PVTi tutorial procedure. Firstly I split the C7+ into SCN45 by Whitson method , then I matched the dewpoint pressure based on the extended composition. Next, I group into 6 pseudo components ( N2C1, CO2+C2+C3, C4 to C6, MCN1,MCN2). I match dewpoint pressure again. Finally , I match other PVT properties. THe viscosity I match the last.
I dont know when we should set weight for dew point pressure to preserve this value in the regression. And which error is the PVT properties compared with the observations after tunning ?( maybe below 5%).
I read the SPE as " New strategy to NEW STRATEGIC METHOD TO TUNE EQUATION-OF-STATE TO MATCH EXPERIMENTAL DATA FOR COMPOSITIONALSIMULATION" or " An effcient Tuning Strategy to calibrate Cubic EOS for Compositional simualtion" But I hardly do these strategies on PVTi. I am really cuirous which solfware these authors use. WHo can help me tho answer above questions? THank you so much.

[Shakespear]

Have a look

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[hoanglongbk88]

Thanks Shakespear, I have read all above documents that you posted here. But I really need some experimence how to realize which PVT properties ( dewpoint pressure, vapor density...) we should match firstly in PVTi? Can I contact with you by emails?my email is nguyenhoanglong2303@yahoo.com.

[Shakespear]

I would read carefully this paper

[link Point to another website Only the registered members can access]
This paper gives you a lot of hints how to do it. Also look up the references !!!
Again, listen to the Whitsen lectures as he talks about this and the regression process.

Yes, the weights needs to be used and the parameters used NEED TO BE constrained so as not to go out of the realistic range for the parameters. Again, this is in the paper and in the Whitson lecture.

Now this is a bonus, Prof. Whitson SHARES his lectures which he gives in Norway University

[link Point to another website Only the registered members can access]
This is education for FREE. I rarely see this done this well, even in places where you would think this should be the norm.

I will try to contact someone who may, I repeat may, help. No guarantee.

You are dealing with a near critical fluid which is not the norm for me and some of my friends. The one things I do know about Near Critical fluids is that it is very very easy to THINK you have matched the data when in fact you have not gotten it right at all.

When I have something I will share it here.

[hoanglongbk88]

I will try to read your papers you posted here carefully. Once again, I am really appreciated your kind help. Hope you can contact someone who used to match PVT model of gas condensate. Thank you very much.

[Shakespear]

Take a look at this also

[link Point to another website Only the registered members can access]
Now this paper deals with QC of the data BEFORE going to the tuning process

[link Point to another website Only the registered members can access]
This is something that Prof. Whitson spends some time explaining in the lectures.

This one is also on the NET. Use GOOGLE.

New strategic method to tune equation-of-state to match experimental data for compositional simulation
by Al-Meshari, Ali Abdallah, Ph.D., TEXAS A&M UNIVERSITY, 2004, 248 pages; 3156484


Abstract:

Since the plus fraction of reservoir fluids has some uncertainty in its molecular weight and critical properties, equation-of-state, EOS, are generally not predictive without tuning its parameters to match experimental data. Tuning of the EOS is found to be the best method for improving the predictions of compositional reservoir simulators.

The proposed strategy for tuning EOS consists of seven steps: (1)?split the laboratory plus fraction to single carbon number groups, SCN, usually up to SCN 44; the last component will be C45+ , (2)?use set of correlations to calculate the critical properties and acentric factor for each SCN group, (3)?match the saturation pressure at reservoir temperature by altering the measured value of the molecular weight of the plus fraction using the extended composition, (4)?group SCN groups to multiple carbon number groups, MCN, (5)?assign critical properties and acentric factor for each MCN group, (6)?rematch the saturation pressure at reservoir temperature using the grouped composition, and (7)?match the volumetric data by regressing on volume shift parameters of all components in grouped composition.

This research shows an accurate method to split the plus fraction to SCN groups. The most accurate set of correlations to calculate the critical properties and acentric factor for each SCN group that will result in a small adjustment for the molecular weight of the plus fraction when saturation pressure is matched using the extended composition. The proposed strategy groups the extended composition to eight pseudocomponents. The binary interaction coefficients between hydrocarbons and between hydrocarbons and non-hydrocarbons are set to zero which dramatically reduces the simulation time.

The strategy proposed in this research for tuning EOS to match experimental data has been tested for a wide range of C7+ mole% (4-25) which covers gas condensate and volatile oil samples. Also, using this strategy to tune EOS at reservoir temperature will accurately predict the fluid properties at separator conditions and saturation pressures at different temperatures.

The scope of this research is to come up with an accurate and systematic technique for tuning an EOS for use in compositional simulation.