The Stratigraphic View

The Stratigraphic View (Views > Stratigraphic View, or Alt+F8 on your keyboard, or the Create option of the context menu in the View Explorer) graphically represents the stratigraphic model. The stratigraphic model defines the stratigraphic hierarchy of the model zonation in the form of 'stratigraphic levels'. By default, three stratigraphic levels exist in the stratigraphic model (but you can change this), with levels on the left being higher in hierarchy then levels on the right. The significance of this hierarchy is explained in The building sequence of surfaces in the 3D structural model.

Each stratigraphic level can contain one or more zones defined by their top and base geological event. Only events of type 'horizon', 'unconformity' and 'intrusion' can be used to define zone boundaries in a stratigraphic model. A right-click context menu is available for each level and zone, with which you can create and edit the different levels and zones. This is important since the hierarchy you define here is used later, when building the structural model, which is in turn used as input for the 3D grid.

You can also choose to build your structural model based on a specific hierarchical level. For example, you can build surfaces for the 3D structural model based on the highest hierarchical level (Level 1) only. You can add zones from another (deeper) hierarchical level to the structural model in a second iteration to create, for instance, infill horizons from markers.

Principle behind 'levels' in the Stratigraphic View

For each event that you assign to the stratigraphic model, a surface will be constructed once you create your 3D structural model. The sequential order of construction of these surfaces, together with the 'internal' construction settings (conformable/proportional to surface above/below) is key to the final layout of the internal zonation of the structural model because each surface is constructed relative to a surface that was previously constructed. Within the set of rules that determine the order of surface construction (explained in The building sequence) two factors are directly related to the stratigraphic model:

Of both factors, the underlying data representation is dominant, with surfaces based on ‘dense’ data representations (i.e. tri-meshes, 2D grids, point sets and polyline sets) always being constructed before surfaces based on ‘sparse’ data representations (i.e. markers). In the application, this is called geometric prioritization, which follows the logic that dense data, typically derived from seismic interpretations, is of higher quality and more continuous than ‘sparse’ data derived from well log interpretations (i.e. markers). Surfaces based on ‘dense’ data are therefore constructed first and constrain the surfaces based on ‘sparse’ data. Within the group of events with ‘dense’ data, first stratigraphic Level 1 surfaces will be constructed, then Level 2, etc. Only when all ‘dense’ data surfaces are constructed, ‘sparse’ data surfaces come into play, following the same hierarchical logic. The combination of geometric prioritization and stratigraphic order, induced by the position of the events in the stratigraphic model, ensures that the internal zonation of the 3D geological model is geologically realistic.

Accessing the Stratigraphic View

The Stratigraphic View is commonly opened as part of the Stratigraphic Modeling workflow in the Stratigraphy strip. In this case, opening the Edit Model form also opens the Stratigraphic View, and the two may be used together when defining the hierarchy. An initial hierarchy is displayed depending on your selection on the Generate Zones form of the workflow.

If a marker set, seismic interpretation or surface set has been assigned, this initial hierarchy is displayed when the view opens. Otherwise, if the Manual option was selected in the Generate Zones form, a blank Stratigraphic View is opened and you can use any of the means described later in this section to manually develop the hierarchy.

To review the stratigraphic model, you can also access the context menu of the stratigraphic model in the JewelExplorer with a right-click and select the option Open In Workflow.

You can open an empty Stratigraphic View by selecting Stratigraphic View from the Views drop-down box in the Workspace section of the Strip.

Creating the stratigraphic hierarchy from existing data

You can leverage existing events in surface sets, marker sets or seismic interpretations to create the initial hierarchy of zones by using the Generate Zones form. The generation of zones uses the relative depth of the event's representations to create the initial zonation order. The zones are created based on the level specified on the form.

For example, if the level of zone generation for a marker set is Level 3, then only one zone will appear on both Level 1 (the highest stratigraphic level) and Level 2. Any zones that are created from the marker set will be assigned to Level 3. As each zone created from a marker set will typically be bound by two well markers, the application will automatically assign a zone name according to the well marker that bounds the top of the zone. These names can be changed by double clicking the zone in the Stratigraphic View or in the Edit Model form by double clicking into the Name column for the zone of interest.

Note that zone names need to be unique per stratigraphic level. With the hierarchy initially generated from a surface set, marker set or seismic interpretation, you can edit the stratigraphic model to correctly define the zone hierarchy. This can be done by inserting, removing, merging, splitting, promoting or demoting the zones as described below. Additionally, more stratigraphic levels can be added (maximum up to Level 9).

The amount of detail depends on the purpose of the model, the complexity of the geology in the model area and the available data. It is important to note that the zones are named after the names used in the marker set, surface set or seismic interpretation.

In the case that the Manual option was selected in the Generate Zones form your stratigraphic model will consist of one zone at Level 1. This will allow you to completely define the hierarchy by hand through the context menus for the zones and levels.

Defining the hierarchy

Zone boundaries in the Stratigraphic Model are orange, but when you have assigned events to them, you can verify whether underlying data is available for those zone boundaries. To do this, select (check) the relevant Seismic Interpretation, Surface Set and/or Marker Set in the JewelExplorer; zone boundaries for which underlying data is present take the color of the events and an [S] or [M] is printed behind the zone boundary name.

As previously noted, all interaction with the hierarchy in the Stratigraphic view is accomplished through the right-click context menu available for each zone and level. Each of the options available in the context menus is described in the table below, the following is a description of the common actions performed via the context menus.

• Managing levels - Levels can be added, deleted and renamed by right-clicking on the 'Level N' text at the top of the hierarchy in the Stratigraphic View. For example, right-click on 'Level 1' if you only have a single level defined.
• Adding zones - Right-click on a zone in the Stratigraphic View and from the context menu select, for example, Insert zone above, Insert zone below, or Split zone at a deeper level. While Insert zone above and Insert zone below will create new zones on the same level as the zone that was right-clicked, Split zone at a deeper level will create a zone on the next deepest level. Note that a zone name needs to be unique per stratigraphic level.
• Assigning geological events - You can assign geological events to the zone's boundaries. These geological events should contain at least one of the following data representations: tri-mesh, 2D grid, polyline set, point set or well markers. From the context menu for a zone, you can select Set top event or Set base event to assign the geological event for each zone boundary. The list contains all events that have not been assigned yet to a zone boundary. From the same context menu, you can also select Insert event from marker to choose an event from a list of available markers.

• Promoting and demoting zones - The Promote zone option will move the selected zone upward in the hierarchy, while demoting a zone with the Demote zone option will move it deeper.
• Splitting and merging zones - Zones without any children can be split. Splitting a zone creates the specified number of zones on the same level as the zone that the context menu was opened from. Zones can be merged as long as they all belong to the same parent zone. To merge zones you will need to Shift+click or Ctrl+click the zones of interest prior to opening the context menu.

Stratigraphic View context menu

Stratigraphic View toolbar

Additional info on zone thickness display

By default, the zone thickness display is set to Relative, where the average zone thicknesses are taken from the input horizons or markers. This thickness is also reflected in the Thickness column of the Edit Model form. When the zone thickness display is set to Equal, all zones on the lowest hierarchical level are displayed with an equal thickness. This is particularly useful if you want to quickly get an overview of all available zones, especially when there is a large thickness variation between the zones (e.g. large overburden). The image below demonstrates the difference between the Relative and Equal zone thickness display settings.

Docking the Stratigraphic View

Like most of the views in the application, the Stratigraphic View, 3D Structure Zonation and 3D Grid Zonation View can be docked at any location in the view.

The zones will scale accordingly, and this way you always have an overview of the created stratigraphy at hand.