EOS7C WARNING. H2O MASS FRACTION IN THE GAS WAS LESS THAN ZERO IN 1 GRID BLOCKS
Hi All,
I got the error below in running TOUGH3-EOS7C. Any idea how to cope with this?
Thanks,
Haiyan
EOS7C WARNING. H2O MASS FRACTION IN THE GAS WAS LESS THAN ZERO IN 1 GRID BLOCKS.
( THE SUM OF CH4, BRINE AND NCG AND TRACER MASS FRACTIONS MUST BE LESS THAN OR EQUAL TO ONE. )
5 replies
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In the past, I have had better success using EOS7C when I specify a very small amount of all components as initial conditions. I use something like 1e-10 for mass fractions, and it does not change the physics of the problem, but sometimes helps numerical issues like you describe.
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Here are a few things to check:
Does your grid resolution change too suddenly? I try to make coarser grid blocks no more than 1.5 times the size of adjacent finer grid blocks.
Do your injection/production rates change suddenly? If it makes sense for your problem, try gradually changing rates with MOP(12)=0.
Try bigger amounts of initial mass fractions: 1e-9 or 1e-8 might help.
Make error criterion RE1 smaller. The default is 1e-5. Try 1e-6.
Check what is happening in the problem when the error occurs. Maybe you can make the problem "easier" for TOUGH by making changes more gradual.
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Sorry I missed the reply. Thanks for the detailed suggestions.
My grid resolution does change significantly, 100m vs 500m. I will try to modify it later.
My MOP(12) is already 0.
I will try the mass fraction.
I did not change the error criterion RE1 as I am afraid the model will run slower. But I can try.
Thanks,
Haiyan
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Christine Doughty said:
Try bigger amounts of initial mass fractions: 1e-9 or 1e-8 might help.This one works in my model. The warnings are all gone. Thanks!
Haiyan