☑️A: RELATIVE PERMEABILITY FUNCTIONS

TOUGH4 retains the same relative permeability functions for two-phase or three-phase flow problems. Table lookup using the user provided table as a new approach has been introduced for both relative permeability and capillary pressure function. To make this report self-contained, we duplicate the Appendix for the discussion of relative permeability functions and the capillary pressure functions from TOUGH3 user manual (Jung et al., 2018).

The three-phase functions from TMVOC and ECO2 start at IRP = 31. For TMVOC, if one of the two-phase functions is chosen, the NAPL relative permeability is assumed to be zero. For ECO2, the two-phase functions are only applicable when an aqueous phase and a single CO2-rich phase are present. If one of the two-phase functions is chosen, the relative permeability of the CO2-rich phase will be the same function of saturation, regardless whether the CO2-rich phase is liquid or gas. The notation used below is: krl – aqueous phase relative permeability; krg - gas (for all two-phase EOSs and TMVOC) or gaseous CO2 (for ECO2) phase relative permeability; krn – NAPL (for TMVOC) or liquid CO2 (for ECO2) phase relative permeability. Sl, Sg, and Sn are the saturations of aqueous, gas (or gaseous CO2) and NAPL (or liquid CO2) phases, respectively.