# Gas-water Model Characteristic curves¶

The gas-water model requires the definition of a capillary pressure curve for the interface between the gas and the water phases, and relative permeability for the water and the gas in water. An example is:

CHARACTERISTIC_CURVES gas_water_example
TABLE swfn_table
PRESSURE_UNITS Bar
EXTERNAL_FILE swfn_file.dat
END
TABLE sgfn_table
PRESSURE_UNITS Bar
EXTERNAL_FILE sgfn_file.dat
END
END


Where the file “swfn_file.dat” contains the water saturation table:

SWFN
0.0    0    0.4
0.1    0    0.3
0.9    1    0.2
1.0    1    0.1
/


The file “sgfn_file.dat” contains the gas saturation table:

SGFN
0.0      0       0
0.10    0.0      0
0.255   0.15     0
0.51    0.4      0
0.765   0.8      0
1.0     1.0      0
/


Note that the capillary pressure entered with the water function table will be used as the aqueous phase/gas phase capillary pressure. The capillary pressure entered with the gas function table will be ignored.