Disappearing gas phase during simulation of CO2 injection

[Guest LenWo_Germany]

Dear all,

I am trying to simulate an injection of CO2 into a brine saturated aquifer with PetraSim 5 (Toughreact 1.2 and ECO2N EOS module (1D, radial)). Everything works fine until the gas saturation Sg in the injection cell reaches full saturation (Sg=1, SG=1-SS approx. 0,95). Then instantaneously the gas phase in all the other cells disappears and the simulation prematurely stops. Also, the solid saturation in cell 1 (injection cell) reduces to 0 and only SG=1 remains. I have tried different solvers and also combinations with preconditioning options, but nothing works. Does anybody have an idea what might be the problem and how it can be avoided? Many thanks in advance!

[Alison]

It is hard to know what the problem is without reviewing the model, but my guess is that the simulation is halting and outputting an incomplete time step, rather than all of the gas phase in the model disappearing.

Depending on the model, it's possible that the SS value in the injection cell is actually going to 1, causing a premature halt to the model. The best way to confirm what is happening is probably to rerun the model with the print options turned on for the injection cell. This will allow you to view a detailed Cell History Plot and will hopefully reveal the problem.

If you continue to have problems, feel free to send me your SIM file and I will take a look.

Best Regards,

Alison

Alison @ rockware.com

[Guest LenWo_Germany]

Hi Alison,

the SS value seems not to be the problem, as it remains relatively constant around 0.05. I will try the print options test and report any advances. Thank you!

Best regards, Lennard

[Guest LenWo_Germany]

Oh, sorry, one correction: SS in the injection cell drops to 0 at the last time step.

[Alison]

I would recommend that you first check to confirm that the Pressure in the model is not exceeding 600 bars. You would normally get a "cannot find parameter" error in the output file for this type of problem.

[Guest LenWo_Germany]

Hi Alison,

no, the pressure does not exceed 600 bars, but is given as NaN in the final output of the last calculated timestep, coinciding with SG=1 in the first cell. I will send you my sim file, maybe you have any idea...

Thank you in advance!!

[Guest LenWo_Germany]

The problem originates in the use of Toughreact 1.2 and some bugs within that old version of the code. If the simulation is run with Toughreact 2 (V2.087), the problem does not appear and the calculation (slowly) converges.