# Characteristic Curves defined by tables¶

Table input is defined within a characteristic curve block, which defines one set of curves in a block. See below example for a set of curves for the GAS_WATER mode:

CHARACTERISTIC_CURVES ch1

TABLE swfn_table
PRESSURE_UNITS Bar
SWFN
0.0    0    0.4
0.1    0    0.3
0.9    1    0.2
1.0    1    0.1
/
END

TABLE sgfn_table
PRESSURE_UNITS Bar
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
/
END

/

The name that follows CHARACTERISTIC_CURVES (e.g. ‘ch1’), allows this data to be associated with a material property. If more than one set of characteristic curves is entered, it is also possible to assign these to cells using the SATNUM keyword in a GRDECL file.

To define the set of saturation curves required by a flow model, the CHARACTERISTIC_CURVES block contains multiple TABLE blocks (see example above).

TABLE takes one compulsory argument, which is the name of the table. This can be given a physical name like ‘sgfn_table’, but that is not required - a unique string like XXX would also work. The names must be unique within each CHARACTERISTIC_CURVES block.

PRESSURE_UNITS is required only for tables that define a capillary pressure. If the table contains a capillary pressure this keyword is compulsory.

The following tables can be specified to enter the data of the saturation curves:

A TABLE block may not contain the data directly - it is possible to include an external file, for example:

TABLE sof2_table
EXTERNAL_FILE sof2_table.dat ! Contains SOF2 table data
END

The tables required by each flow models are given below:

Flow model

Saturation Curves

Saturation Curve Tables

GAS_WATER, COMP3

$$P_{\mbox{cgw}},K_{\mbox{rw}},K_{\mbox{rg}}$$

SWFN, SGFN

BLACK_OIL, SOLVENT_TL, COMP4, COMP

$$P_{\mbox{cow}},P_{\mbox{cog}}K_{\mbox{rw}},K_{\mbox{rg}},K_{\mbox{row}},K_{\mbox{rog}}$$

SWFN, SGFN, SOF3

TODD_LONGSTAFF

$$P_{\mbox{cow}},K_{\mbox{rw}},K_{\mbox{rhw}}$$

SWFN, SOF2

TOIL

$$P_{\mbox{cow}},K_{\mbox{rw}},K_{\mbox{row}}$$

SWFN, SOF2, SOF3

In some cases it may be necessary to make clear the association between the information required and where it is obtained, in which case the keywords PC_OW_TABLE, PC_OG_TABLE, KRW_TABLE, KRG_TABLE, KROW_TABLE and KROG_TABLE can be used. Then it would be possible, for example, take the water relative permeability function from one table and the oil-water capillary pressure from another. For more information see Defining the data in multiple tables.