Table of Contents
Materials are used to define the permeabilities and other properties in an analysis. Each cell is associated with a material. Materials can be assigned to the entire model (when the boundary is created), by region (select a region and edit the region properties), or to individual cells (in the Grid Editor, select a cell or cells). PetraSim uses inheritance to determine any particular cell property: it first looks in the cell; if the property is not found there, it looks in the region; finally it looks in the default model.
When a new model is started, there is one default material. Material data is edited by selecting Properties->Materials... or 
. In this dialog, the user can edit, create, and delete materials, Figure 8.1. The basic material data includes (many are self-explanatory):
Name - The material name that will be written to the TOUGH input file, limited to five characters.
Description - A longer description for user clarity.
Rock Density - Density.
Porosity - Porosity
X, Y, and Z Permeability - The absolute permeabilities are defined in each direction.
Wet Heat Conductivity - Wet conductivity
Specific Heat - Specific heat.
Selecting the Relative Perm... button displays the Additional Material Data dialog. The first tab is used to define Relative Permeability, Figure 8.2. The user selects the desired relative permeability function and then defines the parameters used by that function. A graph will display the permeabilities (magenta->gas and blue->liquid) as a function of liquid saturation.
Select the Capillary Pressure tab to define the capillary pressure function, Figure 8.3. The user selects the desired capillary pressure function and then defines the parameters used by that function. The value of ICP corresponds to the TOUGH function ID. The Help section of www.petrasim.com provides a spreadsheet to plot the capillary pressure functions.
Select the Misc tab to define additional material properties, Figure 8.4. These include:
Pore Compressibility - This defines how the pore volume changes as a function of pressure. This is used when storativity is to be included in the model, such as when performing a well test analysis. In most cases, this is not used and remains 0.0.
Pore Expansivity - The defines how the pore volume changes with temperature. In most cases, this is not used and remains 0.0.
Dry Heat Conductivity - Used with the wet heat conductivity to change the thermal conductivity of the rock.
Tortuosity Factor - The user is referred to Appendix D of the TOUGH2 User's Guide for a detailed discussion of this factor. In most cases, this is not used and remains 0.0.
Klinkenberg Parameter - The user is referred to Appendix A of the TOUGH2 User's Guide for a detailed discussion of this factor. In most cases, this is not used and remains 0.0.
To support the use of geostatistical data, PetraSim allows the user to import a table of material assignments for all cells. This is useful if the user has an independent representation of the model that can be queried to obtain a spatial definition of materials. PetraSim provides two tools:
The capability to write a file with cell IDs and X, Y, Z coordinates.
The ability to paste a table of material types for all cells.
To write a file with cell IDs and X, Y, Z coordinates, select File->Write Grid Data.... This file defines the cell coordinates in their PetraSim order that allows you to query a separate material database.
Select Model->Assign Cell Materials... to open the Assign Cell Materials dialog, Figure 8.5. You can either type or paste a list of materials to be assigned to each cell. All materials must have already been defined. The Material Name must match the name of an existing material.
