Questions about compositional fluid solver

[Pengyu Huang]

Dear All,

I am new to the compositional fluid solver in MRST. I noticed that the equation of the state of the mixtures is calculated from this solver. For example, it can be seen from  "model.EOSModel". I wonder if I want to consider the pressure-dependent density and viscosity of water(or oil phase) in MRST, do I need to modify the properties in model.fluid? Or is it already considered in the compositional solve automatically? All advice is welcome. Cheers.

Regards,

Pengyu

[Olav Møyner]

Daer Pengyu,

If you use a compositional model, the phase properties (density, viscosity) of the miscible phases will be computed by the EoS. For example, for a three phase compositional model the default is that the water is assumed immiscible and uses the regular fluid struct while oil and gas uses the EoS. It is possible to configure the model so that e.g. water and gas is miscible (see the properties "liquidPhase" and "vaporPhase" on the model) in which case the oil phase would be taken from the fluid.

Best regards,

Olav

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From: sinte...@googlegroups.com <sinte...@googlegroups.com> on behalf of Pengyu Huang <hugh...@gmail.com>
Sent: Monday, June 14, 2021 7:09
To: MRST-users: The Matlab Reservoir Simulation Toolbox User Group <sinte...@googlegroups.com>
Subject: [MRST Users] Questions about compositional fluid solver

 

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[Pengyu Huang]

Thank you very much for the reply, Olav! Now it is much clear. 

I know how to add the EOS of water using the fluid struct, so I will try to do it this way. By the way, if I want to model the miscible phase, i.e. in my case will be water and methane, for an initial fraction of [0.45 0.55] (info.initial =  [0.45 0.55]  ), then for the s0 in initCompositionalState(G, info.pressure, info.temp, s0, info.initial, model.EOSModel), do I assgin s0 =  [0 0.45 0.55] for the initial saturation in the reservoir?  Is there a similar example case or tutorial case provided in the MRST code? Thank you again for your help. 

Regards,

Pengyu