EOS7c and NCG injection
Dear all,
I am using EOS7c module, to model the injection of a NCG (either CO2 or N2) in a depleted CH4 reservoir. As soon as the mass fraction of the non-condensible gas X_NCG_G approaches 1 (i.e. X_METHAN_G become small, smaller than let's say 1E-5) the simulation stops after some iterations failure, providing the message
TOUGH STATUS: Failed in EOS. IGOOD= 2
Is this a limitation of the module or am I messing up something?
I have set-up the simulation without diffusion (NB = 6 in MULTI).
The temproary fix I did is injecting a small quantity of methane (<1% of the injected NCG) where the NCG is injected. This way the iterations procede without failure, but maybe there is a more elegant solution.
Any additional suggestion/comment on overcoming the problem is welcome, thanks.
3 replies
-
I would need to see more of your output to know for sure, but I have experienced this sort of thing also. In the original EOS7c, it was a strict requirement that some CH4 always be present, but that was a long time ago, so I doubt you have that version of the code. Turning on diffusion might help. Your temporary fix of co-injecting a little CH4 is something that I have also used successfully - in fact that is my go-to action when component disappearance causes problems. You could also check that your grid resolution does not change abruptly anywhere - that can cause difficulties regarding phase change in general.
-
EOS7C use an iterative approach for solving gas mutual solubility. This approach sometime has the convergence problem and causes failure of the iteration. We are working on a non-iteration method for next version of TOUGH codes.