The Example in TOUGH2's ECO2N：Radial Flow from a CO2 Injection Well

Dear Luo,

two cases are simulated, one is a isothermal problem in which the energy balance equation is not solved (NEQ=3), the second is a non-isothermal problem (NEQ=4) in which the wellbore injection T is held constant at the initial reservoir T of 45°C.

(1) in order to run non-isothermally but with a constant injection T, the rock thermal energy of wellbore block needs to be numerically infinite, either by assigning an infinite rock density and/or an infinite rock specific heat. 

(2) CO2 injection enthalpy can be omitted in both cases. Actually TOUGH2 reads 0 J/kg as CO2 injection enthalpy. This value does not affect the simulations because for the isothermal case the thermal energy balance is simply not solved, while for the non-isothermal case the CO2 injection enthalpy has an insignificant contribution to the energy balance of wellbore block due to the infinite rock thermal energy.

(3) Setting the wellbore block node distance to zero simply reduces the P losses inside the wellbore to a negligible value as we can expect, assuming the wellbore P is applied directly at the sand face.

(4) By using the above input assignments, you should be able to replicate the user's guide simulations for both isothermal and non-isothermal cases.

The user's guide describes the use of the above input assignments quite clearly. Having a look to TOUGH2 balance equations helps in following the user's guide description.

Regards,

Alfredo