Compositional model phase Properties

[Markonemore]

hello

I am trying to calculate fluid properties using the compositional model standaloneFlash.m. It is reasonable to say that when the pressure is less than the bubble point pressure, with the gradual decrease of the pressure, the gas separates from the oil phase, and the density and viscosity of the oil phase should increase. However, the calculated density and viscosity of the oil phase are still decreasing. When the pressure drops to atmospheric pressure, it seems normal. What is the reason?

[Olav Møyner]

Hi,

What is your experimental data and how did you set up your equation of state? Typically you would have to do some tuning of the parameters (for example the binary interaction coefficients) if you want to match experimental data for any given mixture. The same goes for the viscosity calculation: MRST implements the LBC model which may have to be tuned for a specific mixture.

I suspect that you may also be in different phase states for the 1 atm pressure point and the rest.

Best regards,

Olav

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From: sinte...@googlegroups.com <sinte...@googlegroups.com> on behalf of Markonemore <markon...@gmail.com>
Sent: Tuesday, April 15, 2025 12:15
To: MRST-users: The Matlab Reservoir Simulation Toolbox User Group <sinte...@googlegroups.com>
Subject: [MRST Users] Compositional model phase Properties

 

hello

I am trying to calculate fluid properties using the compositional model standaloneFlash.m. It is reasonable to say that when the pressure is less than the bubble point pressure, with the gradual decrease of the pressure, the gas separates from the oil phase, and the density and viscosity of the oil phase should increase. However, the calculated density and viscosity of the oil phase are still decreasing. When the pressure drops to atmospheric pressure, it seems normal. What is the reason?

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[Markonemore]

Thank you for your reply.

The parameters I used have been adjusted, and the experimental data in the figure is the calculation result in CMG-WINPROP. I suspect that MRST only obtained the possible correct phase state at atmospheric pressure. Is the bubble point pressure not considered? At the same time, under the same parameters, the density and viscosity calculated by MRST above saturation pressure still have some deviation from CMG.

[Olav Møyner]

Hi,

I think it is hard for me to debug this without having access to the exact setup you used to produce the plots. We do not really have a CMG input parser, so I presume that you have set this up in a script? The EOS in MRST uses a fairly standard sets of parameters (bics, molecular properties, volume shift) so presumably you have these available together with your test data. If you can share the data (privately by email or here in the list) I could have a look.

Best regards,

Olav

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From: sinte...@googlegroups.com <sinte...@googlegroups.com> on behalf of Markonemore <markon...@gmail.com>

Sent: Tuesday, April 15, 2025 15:13

To: MRST-users: The Matlab Reservoir Simulation Toolbox User Group <sinte...@googlegroups.com>

Subject: Re: [MRST Users] Compositional model phase Properties

 

To view this discussion visit https://groups.google.com/d/msgid/sintef-mrst/47c3e733-9b3b-454b-bc5d-bb53794716cbn%40googlegroups.com.