crashing after reaching equilibrium and starting VOC injection
I am simulating a 3D sand pack test where it is half full of water with some small hydraulic head from one end to another and the oil leaks into the sand at some distance above this water table. So, after generating the mesh, I defined the appropriate BC on both ends while everything else in the middle was disabled and then ran the model until reach a steady state. Then, I fixed both ends and enabled the model cells, and ran again to reach a steady state again. I then updated the cells based on the obtained thermodynamic conditions in the SAVE file. Now I have a water table established nicely across the model based on the desired head.
Next, I started to inject some oil into the sand; however, it keeps issuing an error message that a gas phase appears at the lowermost layer of the model which at the end of the steady state was filled 100% with water (with some small amount of dissolved air). I do not understand why a gas phase should evolve at that point which is far away from the spill point.
Any idea why is this occurring?
Your output shows PG=infinite and this is the cause of the phase switches from aqueous to two phase Aq+G. PG is the sum of partial pressures of components in the aqueous phase and, of course, should not be infinite. In particular when there is no VOC initially dissolved in the aqueous phase and the air content is below its solubility limit at local T.
You are using a custom VOC (called B) for which you entered the necessary parameters in CHEMP block. I simply removed this VOC and included one of the VOC available in the internal data bank supplied by PetraSim. And TMVOC is able to go on, without any phase change in the single aqueous elements.
I suggest you to check the parameters given in CHEMP for your "B" VOC. In particular, the coefficients given to compute its solubility in water and its saturation P.