Temperatures reaching out of range in EOS2 despite no GENER block

Hi all,

I am trying to run a model operating at temperatures close to the maximum modelled by TOUGH (360C) due to the system it is based on. Since this is only 13 C cooler than what is achievable by TOUGH2 I have opted to fix the basal cells to 360 C by maximizing their volume to infinity rather than having a GENER block. This basal layer of cells also has a fixed CO2 partial pressure of 30 bar / 3 MPa, similar to reservoir conditions found at the depth of the system I am modelling. The rest of the model starts with 0 CO2 partial pressure.

However, the model finishes prematurely, stating that temperatures are out of range in many blocks that seem to have no correlation. How can this be possible if there is nothing to raise these cells above supercritical temperatures? 

Is this due to phase changes / boiling / the addition of CO2? Models without a CO2 component run without a problem. I have considered the injection of CO2, but I have no data to reference the rate at which is injected.

 Any advice would be greatly appreciated.

Cheers,

Hamish J