Modification of gas dissolution in water phase in the compositional module

[ahmadreza shojaee]

Dear all,

I hope you are doing well. I have a question about the compositional module. In the compositional module, it is possible to set water phase as the liquid phase to simulate gas water displacement scenarios. However, EOSs in this module, predicts wrong values for gas dissolution in the water phase (x vector: mole fraction of each component in the liquid phase). For example, take a look at the attached. figure. I performed a simulation using CMG-GEM, ECLIPSE, and MRST. The below chart shows the mole fraction of CO2 in the water phase:

 Unfortunately, EOSs predicts wrong solubility for gas components in the water phase. 

In CMG-GEM, the approach of modeling gas dissolution in water is using henry's law, and it does not use any EOS to calculate that. However, ECLIPSE applied a modification in the EOS in the GASWAT model to improve gas dissolution prediction using EOS. This modification is known as Soreide and Whitson approach as follows:

I am wondering how we can apply these changes for the water component in MRST. If this modification would be applied into the MRST compositional module, it gives us more flexibility to solve water-gas systems!

Kind regards,

Ahmad

[Olav Møyner]

Hi,

At the moment there is no difference in phase behavior if you set the water phase as compositional versus the oil phase. This option is primarily intended to get the right phase labels, and allows MRST to be a bit more flexible when you have a specific rel. perm set up. It is up to the user to set parameters for the EOS to get the correct behavior. As you correctly note, different simulators make different choices for the aqueous phase. We do not have any plans or ongoing projects where e.g. the Whitson-Søreide modification will be implemented, unfortunately, but if someone would implement this we would be happy to incorporate it in the public MRST release.

Best regards,

Olav

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Subject: [MRST Users] Modification of gas dissolution in water phase in the compositional module

 

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[ahmadreza shojaee]

Dear Olav, 

Thanks for your answer. I believe adding this feature to the compositional module gives us more flexibilities to model complex gas-water systems in a general format. I would like to do that, but it takes a lot of time for me to find how EOS is treated among many functions. Is there any source or flowchart describes how and where the EOS is treated in the codes. I think this modification should not be hard as only it is changing one parameter only for water component (it would make it as a function of temperature and salinity). The other changes are binary interaction coefficient that can be entered manually.

Kind regards,

Ahmad