Exporting Grid Models

Currently, Petres supports exporting grids to the Eclipse .GRDECL file format, which is especially used for Corner-Point grids.

Exporting a grid to .GRDECL file typically includes:

• Grid geometry (SPECGRID, COORD, ZCORN)

• Active cell mask (ACTNUM)

• Optional grid properties (e.g., PORO, PERMX)

Note

For a comprehensive understanding of the underlying keywords, refer to the Corner-Point Grid Representation in ECLIPSE section.

Exporting Grid Geometry

CornerPointGrid can be exported directly to a .GRDECL file:

grid.to_grdecl("model.grdecl")

By default, the active cell mask ACTNUM is included in the export. To exclude it:

grid.to_grdecl("example_grid.grdecl", include_actnum=False)

This is useful when you prefer to manage the active cell definition separately in your simulation setup.

Note

The exported GRDECL file can be incorporated into an Eclipse simulation by including it within the GRID section of the simulation DATA file using the INCLUDE keyword:

GRID

INCLUDE
'path/to/example.grdecl' /

The GRDECL file contains the grid definition (e.g., COORD, ZCORN, ACTNUM) and typically includes a SPECGRID keyword. However, SPECGRID is used only for internal consistency checks and does not replace the required grid declaration in the RUNSPEC section.

Therefore, the grid dimensions must be explicitly defined using the DIMENS keyword in RUNSPEC section:

RUNSPEC

DIMENS
Ni Nj Nk /

where Ni, Nj, and Nk denote the number of grid cells in the i, j, and k directions, respectively. These values must be consistent with the dimensions of the exported grid.

Important

When importing the exported grid into Petrel, the y or z axes may appear inverted. Petrel may automatically apply a -1 sign flip internally to preserve a right-handed coordinate system. This is normal behavior and does not necessarily indicate an issue with the exported .GRDECL file.

Exporting Grid Properties

Grid properties can be exported together with the geometry:

# Create a porosity property
poro = grid.properties.create(
   name="porosity",
   description="Porosity",
   eclipse_keyword="PORO",
)
poro.fill(0.2)

# Export grid with selected properties
grid.to_grdecl(
   "model.grdecl",
   properties=["porosity"]
)

Important

If the properties argument is not defined in to_grdecl(), all existing properties will be exported by default.

Each property is written using its associated simulator keyword defined during property creation (e.g., PORO, PERMX).

It is also possible to export a property without the grid geometry:

poro.to_grdecl("porosity.grdecl")

Note

In order to export a property, the eclipse_keyword variable must be filled when creating the property.