Tuning EOS parameters

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.

which cubic EOS's are you used?

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

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.

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

[QUOTE]I have read the PVTi manual [/QUOTE]
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

[url]http://www.escet.urjc.es/~sop/alumnos/proyectos/descargas/propuesta04.pdf[/url]

[url]ftp://78.39.200.210/FTP%20server/Teacher/montazere/Gas%20Condensate%20Papers/Science%20Direct/[/url]

[url]http://faculty.ksu.edu.sa/kelshreef/Publication/New%20correlations%20calculate%20volatile%20oil,%20gas%20condensate%20PVT%20properties.pdf[/url]

[url]http://www.fekete.com/resources/papers/four_reasons_gas_condensate_paper.pdf[/url]

[url]http://www.pvtsim.com/modules-packages/pvt-lab/pvt-simulation.aspx[/url]

[url]http://www.pe.tamu.edu/wattenbarger/public_html/PETE%20611_Wattenbarger/pete611notes/chap5_611.pdf[/url]

Whitson's lecture stressed what is in this paper
[url]http://www.onepetro.org/mslib/servlet/onepetropreview?id=00064520&soc=SPE[/url]

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.

[url]ftp://78.39.200.210/FTP%20server/Teacher/montazere/Gas%20Condensate%20Papers/SPE/00091505.pdf[/url]

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.

Have a look

[url]http://www.petrostreamz.com/admin/uploads/whitepapers/GasCondensatePVT.pdf[/url]

[url]http://www.spe.org/jpt/print/archives/2001/07/JPT2001_07_DA_series.pdf[/url]

[url]http://www.weatherfordlabs.com/LinkClick.aspx?fileticket=DhVs75si85w%3D&tabid=133[/url]

[url]http://www.egpet.net/vb/threads/8116-Acentric-factor-%28equation-of-state%29[/url]

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 [email]nguyenhoanglong2303@yahoo.com[/email].

I would read carefully this paper

[url]ftp://78.39.200.210/FTP%20server/Teacher/montazere/Gas%20Condensate%20Papers/SPE/00081113.pdf[/url]

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

[url]http://www.ipt.ntnu.no/~curtis/courses/PVT-Flow/2010-TPG4145/[/url]

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.

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.

Take a look at this also

[url]http://lib3.dss.go.th/fulltext/Journal/Ind.Eng.Chem.Res/2000v39no12/no.12/2000v39no12p5029-5036.pdf[/url]

Now this paper deals with QC of the data BEFORE going to the tuning process

[url]http://www.hycal.com/old/PDFPapers/Reservoir%20Optimization/Reservoir%20Fluid%20Sampling%20&%20Recombination.pdf[/url]

This is something that Prof. Whitson spends some time explaining in the lectures.

This one is also on the NET. Use GOOGLE.

[QUOTE]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.[/QUOTE]

You sent to me the dissertation of Ph.D "New strategic method to tune equation-of-state to match experimental data for compositional simulation" 1 or 2 months ago.
I followed the strategy the Al-Meshari, Ali Abdallah, Ph.D proposed. There are 7 steps. I try to do exactly as he wrote. But it is so hard to do on PVTi exactly.
do you have any gas condensate datta , such as components analysis, CVD test, CCE test that I can do on PVTi?

I would look through these papers

[url]ftp://78.39.200.210/FTP%20server/Teacher/montazere/Gas%20Condensate%20Papers/[/url]

and look in the text book

"Phase Behavior of Petroleum Reservoir Fluids"

Take a look on page 440

Ahmed-T-Equation-of-State-and-PVT-Analysis.pdf

Then go to references

Also a very good explanation of the tuning steps in the Petroleum Experts PVTP manual

[url]http://www.fanarco.net/books/reservoir/PVTP_COMPLETE.pdf[/url]

look at the Worked Examples

[QUOTE]If no other factors such as system integration influence the selection we would recommend PATH 1 to find a matched EoS. With integrated systems the surface facilities modeling package may not allow the changing of pure component properties. In this case select the approach outlined in PATH 2.

PATH 1

Start with all Tcs and Pcs selected (except for N2 and CO2).

If BI coefficients are available select the value between C1 and the heaviest component.

The reason AFs are not chosen initially is that they have a tendency to be pushed to extreme values which in turn lifts the low temperature end of the Phase Envelope to near vertical. Using Tcs and Pcs give a gentler and more controlled path to a solution.

If using Tcs and Pcs does not result in convergence, start adding AFs.

If Volume Shift is required select some Si component properties. Please note that Volume Shift is not recommended until no other combination is found to work( see Volume Shift for more details)

There may be some objections to using the properties for pure components below C6 since they are measurable.

We have found the above method to work universally. however, we do not prevent the user from selecting any combination of properties or approaching the solution differently.

PATH 2

The requirement to hold pure component properties means that the overall matching process becomes more difficult and the approach must change almost from the beginning to maximize the matching possibilities. Create a composition with 5 or more pseudo components. Use the Whitson gamma method within the Advanced Splitting Dialog to get the best set of pseudo components. Add BICs where practical.

Use the Preferences Dialog to switch off regression with pure components. In the Regression Parameter Dialog select all pseudo component Tcs and Pcs and any BICs that may be available. Initially match with volume shift off.

If match is not adequate add volume shift and pseudo AFs to the match parameters. With the restrictions placed on the match parameters it may not be possible to fully match all the properties of the fluid.

The problems encountered with heavily volume-shifted compositions basically arise from an inconsistency in mass balance. Much work has been done within the IPM suite to reduce the effects of this. If volume shift cannot be eliminated then its late inclusion to the match will help to reduce its effect.

See also Step by Step Guide (Appendix A) for a detailed methodology in creating a fully matched composition by either path.

[/QUOTE]

Shakespears, after you tune the PVT model, How can you validate whether your model is right or not?

If you are using PVTi, you will see how good things are through the Regression Report. Another way is through PLOT option for your different experiment data (CCE, DL etc.) which will show a plot of the regression results and the experimental data for different properties and parameters.

I have been going through the "WORKFLOW" example for PVTi and must say it is confusing. It was better described in a much older version of PVTi. Not sure why, but it seems that someone who knew it very well made one too many options of how a fresh user would interpret the written description.

However in the end this is a TRIAL-and-ERROR process.

The person who I thought might be the best source of info on the regression process has so far not responded :-(

Notice that Petroleum Experts PATH1 and PATH2 has lots of similarity to the "WORKFLOW" tutorial for PVTi.

Does anyone have access to this paper

[QUOTE]A systematic investigation into the most suitable data for the development of equations of state for petroleum reservoir fluids

Robert C. Merrill, Jr.a and Trevor M.J. Newleyb

aBP Research International, Sunbury Research Centre, Chertsey Road, Sunbury-on-Thames, Middle--- TW16 7LN Gt. Britain

bBP Exploration (Alaska), P.O. Box 196612, Anchorage, Alaska 99519 USA

10 August 2001[/QUOTE]

I have tried to match the PVT of gas condensate with observations from experiment by trial and error process. But I can't match all the observations exactly simultaneously. The errors of Liquid volume ( in CCE and CVD) and vapor viscosity in CCE are very large. Can you take a look of my PVT file? I can send it to you. Can you give me your email? my email is [email]nguyenhoanglong2303@yahoo.com[/email].

A good paper

"How many components ... "
[url]http://www.brilabs.com/LinkClick.aspx?fileticket=DhVs75si85w%3D&tabid=133[/url]

[URL="http://repository.tamu.edu/bitstream/handle/1969/1388/etd-tamu-2004C-2-PETE-Al-Mesha.pdf?sequence=1"]Tuning - Dissertation[/URL]

hoanglongbk88 - Take a look at the graphs of the tuning results in this paper. Pay special attention to the Liq. Saturation CVD data. Tell me what you see.

Liq. Sat. experiment is IMPORTANT because it is the one that will model how much condensate will come out of the gas. Hence that will decide how much will be left in the reservoir if you pressure drops below Dew Point.

Dew Point is also important as it will effect the point on the Liq. Sat. curve at which condensate (Liq. Sat.) starts to drop out.

In you data these are the things that are the biggest problem from what I saw. The rest looked good.

I would suggest to carefully spend the time DOING tutorials "Regression" (R) and "Workflow" (W) to fully understand how PVTi works. For instance you have "Superimpose" button. Do you know why? Then in "W" they tell you to CLOSE the project without saving. Do you know why? ....

Let me know here as this will help others.