Characteristic Curves defined by analytic options

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

And example is reported below:

CHARACTERISTIC_CURVES drainage
  PC_WG VAN_GENUCHTEN
  ALPHA 5.0D-5
  M 0.457
  WATER_CONNATE_SATURATION 0.2
  WATER_RESIDUAL_SATURATION 0.3
  MAX_CAPILLARY_PRESSURE 1.0d7
END

KRW MOD_BROOKS_COREY
  M 2.0d0
  WATER_CONNATE_SATURATION 0.2
  WATER_RESIDUAL_SATURATION 0.3
  SMOOTH
END

KRG MOD_BROOKS_COREY
  M 2.0
  GAS_CONNATE_SATURATION 0.0
  GAS_RESIDUAL_SATURATION 0.05
  SMOOTH
END

TEST
/

The user specifies the saturation function to be defined analytically and the type of analytical function to use. The parameters required to define the saturation function are entered in the sub- keywords of the instruction block specific to the chosen analytical form.

Below is the list of saturation functions that can be defined analytically, and the keywords to be used in the input:

Block name

Alias

Defines

CAP_PRESSURE_FUNCTION_WG

PC_WG

Gas-water capillary pressure \(P_{cgw} =P_g - P_w\)

CAP_PRESSURE_FUNCTION_OG

PC_OG

Oil-gas capillary pressure \(P_{cog} =P_g -P_o\)

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.

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