# SIMULATION¶

Defines the flow model to simulate. See below an example to define a GAS_WATER case running in isothermal mode:

SUBSURFACE_FLOW Flow
MODE GAS_WATER
OPTIONS
ISOTHERMAL
RESERVOIR_DEFAULTS
/
/


Here is an unlikely example showing every one of the keywords which will be described below:

SUBSURFACE_FLOW Flow
PREAMBLE
MODE GAS_WATER
OPTIONS
ISOTHERMAL
RESERVOIR_DEFAULTS
NOGASSOL
ANALYTICAL_JACOBIAN
HYSTERESIS
HYSTERESIS_PC 0.1
TL_OMEGA 0.5
/
CHECKPOINT
[checkpoint block]
/
restart test-23.0000y.h5
ERESTART base 3000 d
/


Below is a list of all options that can be specified in the SIMULATION block:

## MODE¶

The MODE keyword selects the flow model for the simulation, and can take the following arguments: BLACK_OIL, GAS_WATER, TOIL_IMS, TODD_LONGSTAFF, SOLVENT_TL. MODE must be entered by the user as it cannot be defaulted.

## ISOTHERMAL¶

Goes in the OPTIONS block of SIMULATION.

If present, the model will run as isothermal, maintaining the same temperature as given in the initialization. All flow models run with the thermal option as default.

## WATER_VISCOSITY_NOSALT¶

Used only by the GAS_WATER model, set that the water viscosity to be modelled with fresh water table, not accounting for the presence of dissolved salt in brine. Required for numerical back-compatibility with OGS-1.4.

## NOGASSOL¶

Goes in the OPTIONS block of SIMULATION. See the following example:

SIMULATION
SIMULATION_TYPE SUBSURFACE
PROCESS_MODELS
SUBSURFACE_FLOW Flow
MODE GAS_WATER
OPTIONS
RESERVOIR_DEFAULTS
ISOTHERMAL
NOGASSOL
/
/
/
END  !! end simulation block


This is valid only for the GAS_WATER module: if present turns off the the solution of gas in the aqueous phase.

## RESERVOIR_DEFAULTS¶

Goes in the OPTIONS block of SIMULATION.

If present causes PFLOTRAN to automatically set some values that are commonly useful for simulating reservoir models. It is possible to use RESERVOIR_DEFAULTS and still override any of the selected defaults by using the appropriate keyword in the corresponding card. A message will be output warning that a RESERVOIR_DEFAULTS default has been overridden in this way.

The values set by RESERVOIR_DEFAULTS are listed in reservoir defaults values.

## ANALYTICAL_JACOBIAN¶

Goes in the OPTIONS block of SIMULATION.

If present, causes the derivatives in the Jacobian matrix to be computed analytically instead of approximated. Leads to better convergence of the nonlinear solver in most cases.

This is available for the following modes: BLACK_OIL, GAS_WATER, TOIL_IMS, TODD_LONGSTAFF, SOLVENT_TL.

Note that this option is automatically selected as part of RESERVOIR_DEFAULTS.

## HYSTERESIS¶

Goes in the OPTIONS block of SIMULATION. See the following example:

SIMULATION
SIMULATION_TYPE SUBSURFACE
PROCESS_MODELS
SUBSURFACE_FLOW Flow
MODE GAS_WATER
OPTIONS
RESERVOIR_DEFAULTS
ISOTHERMAL
HYSTERESIS
/
/
/
END  !! end simulation block


Activate the relative permeability hysteresis modelling in the simulation using the Carlson model [C+81]. The user must supply the indices of the required CHARACTERISTIC_CURVES sections to be used for the imbibition process using the IMBNUM grid keyword.

Available in GAS_WATER mode only.

## HYSTERESIS_PC, EHYST¶

Goes in the OPTIONS block of SIMULATION.

HYSTERESIS_PC specifies the curvature parameter for capillary pressure hysteresis, [Kil76]. It takes a number as argument, which must be greater than zero. See example below:

HYSTERESIS_PC 0.1


When HYSTERESIS_PC is entered both the capillary pressure and relative permeability hysteresis are active. The user must supply the indices of the required CHARACTERISTIC_CURVES sections to be used for the imbibition process using the IMBNUM grid keyword.

## RESTART¶

RESTART specifies the file that contains a previous state of the simulation in PFLOTRAN format, from which the simulation can be restarted. It takes a file name as argument. For more details see RESTART. An example is given below:

RESTART restart_file.h5


If not specified, the simulation starts from its initial state.

## ERESTART¶

ERESTART specifies the file that contains a previous state of the simulation in Eclipse format restart file, from which the simulation can be restarted. Takes as an argument a file name. For more detail see ERESTART. An example is given below:

ERESTART base 3000 d


If not specified, the simulation starts from its initial state.

## CHECKPOINT¶

Define instructions to save the simulation states for a given set of times. For more details see CHECKPOINT. An example is given below:

CHECKPOINT
FORMAT HDF5
PERIODIC TIMESTEP 20
/


## TL_OMEGA¶

Goes in the OPTIONS block of SIMULATION.

Only required for the TODD_LONGSTAFF and SOLVENT_TL modes.

Takes one argument, which specifies the Todd-Longstaff model omega value, which may lie between 0 and 1. The default value is 0. An example is given below:

SUBSURFACE_FLOW Flow
MODE  TODD_LONGSTAFF
OPTIONS
ISOTHERMAL
RESERVOIR_DEFAULTS
TL_OMEGA 0.5
/
/


Goes in the OPTIONS block of SIMULATION.

For advanced users or debugging purposes only.

Causes additional information about PFLOTRAN_OGS to be written to the .out file, under the heading PROVENANCE.

The time and date of compilation and the current PFLOTRAN_OGS Git commit can always be found in this section. When the keyword ABOUT is included, much more detailed information about the compilation and version control is included.

## PREAMBLE¶

Goes in the OPTIONS block of SIMULATION.

Causes some additional information about the run setup to be output to the screen before the run starts. This information can also be found in the run’s .out file by default.