Porosity change by pressure change in TOUGHREACT
Hello, TOUGH community,
In my flow simulation with TOUGHREACT, I observe pressure changes by fluid injection.
Here, I find that without chemical reactions, there is no porosity change at all even with changing pressure.
I used rock compressibility in the ROCKS block in flow.inp. WIth this setting, I could model the porosity change in the TOUGH2 and TOUGH3.
In TOUGHREACT, is there any other input option that I need to assign to see the porosity change by pressure change?
Thank you for your consideration.
3 replies
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Hi Kyung Jae,
In TOUGH2 the pore compressibility changed the porosity internally only for the pressure calculation, but did not "update" that modified porosity (porosities were only stored as an unchanging rock parameter). Changing porosity using the pore compressibility can be done in TOUGHREACT with this revised MOP parameter:
MOP(23) = 0 Coupling of pressure to porosity changes
= 1 No coupling of pressure to porosity changes
However, while using pore compressibility to change porosity is a good way to model pressure changes in porous media, it assumes the rock grains are compressible and there is no grid block volume change. This does not accurately conserve mass for reactive-transport. Those mass balance errors may not be very large, unless the compressibility is set large and the porosity changes significantly. So we have a MOP option to choose whether to update the porosity. Either way the compressibility is used internally to modify the porosity. Now that I read the description, it should say "update in the porosity owing to pressure changes".
cheers,
Eric