# Characteristic Curves defined by analytic options¶

PFLOTRAN-OGS has a large range of options for entering saturation function data using analytic functions. These are detailed in Analytical Options for Characteristic Curves.

To define characteristic curves with analytical functions the following blocks within the characteristic curve block may be used. Each of these blocks may select the function which is required, and provide the required parameters.

Block name

Alias

Defines

CAP_PRESSURE_FUNCTION_OW

PC_OW

Oil-water capillary pressure $$P_{cow} =P_o - P_w$$

CAP_PRESSURE_FUNCTION_OG

PC_OG

Oil-gas capillary pressure $$P_{cog} =P_g -P_o$$

PERMEABILITY_FUNCTION_WAT

KRW

Water relative permeability $$K_{rw} (S_w )$$

PERMEABILITY_FUNCTION_GAS

KRG

Gas relative permeability $$K_{rg} (S_g )$$

PERMEABILITY_FUNCTION_OW

KROW

Oil-in-water relative permeability $$K_{row} (S_w )$$

PERMEABILITY_FUNCTION_OG

KROG

Oil-in-gas relative permeability $$K_{rog} (S_g )$$

PERMEABILITY_FUNCTION_OIL

KRO

Oil relative permeability $$K_{ro} (S_w ,S_g )$$

PERMEABILITY_FUNCTION_HC

KRH

Hydrocarbon-in-water relative permeability $$K_{rhw} (S_w)$$ (similar to KROW, but applies to hydrocarbon $$S_h =S_o +S_s$$)

For details of these correlations, please consult Analytical Options for Characteristic Curves. An example of their use in a two-phase oil case is:

CHARACTERISTIC_CURVES ch1
CAP_PRESSURE_FUNCTION_OW VAN_GENUCHTEN
WATER_CONNATE_SATURATION 0.2
WATER_RESIDUAL_SATURATION 0.2
M 0.5d0
ALPHA 5.792e-05
MAX_CAPILLARY_PRESSURE 0.d0
!SMOOTH ! When using smoothing option
/
PERMEABILITY_FUNCTION_WAT MOD_BROOKS_COREY
M 2.0d0
WATER_CONNATE_SATURATION 0.2
WATER_RESIDUAL_SATURATION 0.2
END
PERMEABILITY_FUNCTION_OW MOD_BROOKS_COREY
M 2.0d0
OIL_RESIDUAL_SATURATION 0.2d0
END

TEST
/


TEST is an optional keyword that that print the saturation functions on ASCII files, with the following naming:

• <characteristic_curves_name>_pcxw_sw.dat

• <characteristic_curves_name>_pcog_sg.dat

• <characteristic_curves_name>_wat_rel_perm.dat

• <characteristic_curves_name>_gas_rel_perm.dat

• <characteristic_curves_name>_ow_rel_perm.dat

• <characteristic_curves_name>_og_rel_perm.dat

• <characteristic_curves_name>_oil_rel_perm.dat