I use the TOUGHREACT EOS1 to model chemical reactions in porous media. In the Permeability-Porosity relation, I choose the Verma-Pruess correlation. The equation is k/ki=(phi-phi_c/phi_i-phi_c)^n.
In the model, I choose the phi_c as 0.46 and the n as 10. However, the simulation result doesn't match the correlation and the chosen parameters.
The initial porosity is 0.5, the critical porosity is 0.46 and the exponent is 10. The expected k/ki is 0.00166, however, the simulation result is 0.48387. I wonder if I miss another keyword causing this issue.
Even though I didn't have the source code, there is a hyperthesis in this Verma-Pruess correlation issue: if we set poro_c =0.46 and n =10, the simulator will take poro_c =0.23 and n =10 as input. That means they will take half of the poro_c and original n as simulation input. Although poro_intial is 0.5, we can put 0.8 for the poro_c keyword in chemcial.inp to make the true poro_c as 0.4. This hyperthesis will give a decent match between expectation and simulation result.
Hope some guys who have the source code can prove that.
Have a great day!