[Paraview] pre processor tough2 geothermal reservoir simulator

[Johan de Koning]

Hello,

I am using a geothermal reservoir simulator called Tough2. For 
post-processing I use Paraview.
Now I am also looking for an open source pre-processing software that 
can create grids. It has to be flexible since I plan to explicitly model 
natural fractures that are present in the underground reservoirs that 
contain the hot water. Does anyone have a suggestion?

Thanks in advance,

Johan