# SNAPSHOT_FILE¶

The SNAPSHOT_FILE sub-block of OUTPUT requests that the simulation outputs HDF5 format files. See example below:

OUTPUT
FORMAT HDF5
MASS_BALANCE_FILE
PERIODIC TIMESTEP 1
END
SNAPSHOT_FILE
TIMES d 30 500 1000
VARIABLES
TEMPERATURE
GAS_SATURATION
LIQUID_SATURATION
GAS_PRESSURE
LIQUID_PRESSURE
END
END
PRINT_PRIMAL_GRID
END


The instructions above output 3D snapshots of the variables on the entire reservoir domain at given times (30 500 and 1000 days), for visualisation in Paraview.

The following options can be used to tune the SNAPSHOT_FILE output:

## FORMAT¶

The FORMAT sub-block of OUTPUT specifies the format of the SNAPSHOT_FILE, and can take the following values:

• HDF5 to include all printed times in the same file.

• HDF5 MULTIPLE_FILES to include each printed time in a different file.

If FORMAT is not entered, no snapshots files are saved.

Note that the PRINT_PRIMAL_GRID sub-block of OUTPUT is required when using GRDECL grids and the HDF5 output format.

Note that the HDF5 format uses an external library for high performance parallel input/output operations (https://www.hdfgroup.org/). In the version downloaded with PETSc, a issue has been encountered with this library, which makes the software write an empty grid file (-domain.h5), when running pflotran in parallel (np >1). The problem has a work around: generate the -domain.h5 file containing the grid geometry information running pflotran sequentially (np = 1), save the file in a different folder to avoid it gets overwritten by successive parallel runs, run the simulation in parallel, copy back the -domain.h5 file generated earlier to visualise the results.

## TIMES¶

The TIMES sub-block of SNAPSHOT_FILE takes one argument that specifies a time unit, followed by a generic number N of arguments that are the times for which simulation states must be saved. See example:

SNAPSHOT_FILE
TIMES d 5 30 100 500 1095
END


## PERIODIC TIMESTEP¶

The PERIODIC TIMESTEP sub-block of SNAPSHOT_FILE takes one argument, which is the number of time steps between two consecutive simulation states to be saved. See example:

SNAPSHOT_FILE
PERIODIC TIMESTEP  10
END


## PERIODIC TIME¶

The PERIODIC TIME sub-block of SNAPSHOT_FILE takes two arguments: the first is the time between two consecutive simulation states to be saved in the restart files, the second is the time unit, see example below:

SNAPSHOT_FILE
PERIODIC TIME  20 d
END


## VARIABLES¶

The VARIABLE sub-block of SNAPSHOT_FILE is a multiple-line instruction block, starting with the keyword VARIABLE and ending by END or ‘/’.

The variables that can be output are model-dependent. Below a the list of variables available for TOWG and TOIL_IMS grouped by fluid phase and material properties, using the syntax expected within by the VARIABLE block:

• OIL_PRESSURE, OIL_SATURATION, OIL_DENSITY, OIL_MOBILITY, OIL_ENERGY

• GAS_PRESSURE, GAS_SATURATION, GAS_DENSITY, GAS_MOBILITY, GAS_ENERGY

• LIQUID_PRESSURE, LIQUID_SATURATION, LIQUID_DENSITY, LIQUID_MOBILITY, LIQUID_ENERGY

• TEMPERATURE, POROSITY, PERMEABILITY_X, PERMEABILITY_Y, PERMEABILITY_Z

Note that the GAS variables are available only for the TOWG flow model, and that LIQUID refers to water. Each variable to print must be included in a single line.

If no VARIABLES are specified, the flow model default set of variables will be printed.