Need Help Choosing EOS Module

Hi everybody, 

I'm pretty new to TOUGH2 MP. I'm hoping somebody can help me, which EOS module should I use?

To modeling natural gas production and reservoir compaction I use FLAC3D with a 3D hydro-mechanical model, because FLAC3D is not so good at calculation for gas flow, so I think, I should try TOUGH-FLAC. After reading the user's guide, I still don't know, which EOS module should I use? In the gas reservoir, there is more than 80% CH4, 10% N2, and a little CO2, but I think, it can be simplified to just CH4 and all this are gas phase.

Thank you,

Gang