Assigning data

After creating a 3D grid, the next step is to assign a 3D structural model to it. In this process, the 3D grid zonation is generated, which uses the original stratigraphic model (which was assigned to the 3D structural model). This means that changes made to the stratigraphic model after assigning it to the 3D structural model (i.e. the stratigraphic model and the 3D structure zonation are out of sync) will also appear here, which can potentially lead to unexpected gridding results. It is advised to always keep the stratigraphic model, the 3D structure zonation and the 3D grid zonation in sync.

In this step, you can select up to which stratigraphic level you want to build your 3D grid (by default the level of the input 3D structural mode is selected), which determines the hierarchical complexity. Furthermore, you can select the vertical interval for which you want to build the 3D grid. Only events present at Level 1 of the associated stratigraphic model are available for selection, so that the construction hierarchy of the grid is not compromised.

To assign data

1. Open the Assign Data form (model > 3D Grid > Assign Data).
2. Select the 3D grid you want to use in the drop-down list, and select the structural model you want to assign from the Structural model drop-down list.
3. Optionally, under the Constrain 3D Grid section you can further specify your 3D grid:
• Stratigraphic level - You can select the stratigraphic level up to which you want to build the 3D grid. The levels available for selection refer to the levels of the stratigraphic model that you assigned to your (selected) 3D structural model. By default, the same level is selected as to which the 3D structural model was built.
Important   You can select a deeper stratigraphic level than the level at which the 3D structural model was constructed. For deeper stratigraphic levels (than used to construct the 3D structural model), only marker data can be used to constrain the zones: dense data representations cannot be used. If no marker data is available, the zones will still be built, but will be unconstrained by so called 'empty events'. If you have dense event data that you want to use for building the 3D grid, make sure it is part of the input 3D structural model.
• Top event / Base event - You can select the vertical extent of the 3D grid, i.e. create a 3D grid subset. The events available for selection are the events present at the highest level (Level 1) of the stratigraphic model. By default, the top and base events of Level 1 are selected.
Important  If your model contains an unconformity or intrusion, review whether this discontinuity may have an impact on (i.e. truncate) the zones in your subset selection. In that case, make sure to include the discontinuity in the fault model and in the vertical selection, for the truncation to be honored in the 3D grid. See How to model an unconformity.
4. Click OK to go to the next step in creating a 3D grid, Editing your model.

Reassigning data

When you reassign to an existing 3D grid (i.e. click Apply or OK on the 3D Grid assign form), all the settings on the Edit Model form are reapplied, based on zone and event names. In this way, settings such as the number of K-layers are kept wherever they can. If no such match is found for zone and event names, the default settings are kept.