Editing the zonation

Name  Lists the names of the zones present in the model at the selected stratigraphic level (Level 1, Level 2, Level 3, etc.). The name of each zone can be edited. Double-click on the name to edit.

Top Event  The name of the event that is assigned to the top of the zone (read-only).

Base Event  The name of the event that is assigned to the base of the zone (read-only).

Layering Type  Here you specify how layers are inserted into the selected zone. This has no effect on the bounding surfaces of the zone itself. However, it determines how elements located on a deeper structural level are aligned relative to the zone. This control is especially useful when markers are used to create infill horizons. You can choose between four different options: Proportional, construction: top to base; Proportional, construction: base to top; Conformable to top; Conformable to base.

Proportional  All child zones will be modeled proportional to the corresponding bounding top (top to base) or base surfaces (base to top). The proportional methods are most effective when there is a lack of markers or seismic interpretation data with which the surface construction can be constrained. For more information on how this option affects the results, see Using the Proportional construction method.

Conform  All child zones will be modeled conformable to either the top or base surface (the example is Conform Top). Layering type settings are visualized in the 3D Structure Zonation View. Indicated with P (proportional) and C (conform) icons at the top or base of the zone. The Layering Type settings are disabled when there are no child zones that can be modeled. Note that a level is added before the Level 1. Settings for this level are set in the bottom drop-down box in the Edit Model form: Layering type for Zones in level 1.

Display  You can specify the display thickness here to ensure a good display of your stratigraphic model in the 3D Structure Zonation View. Note that editing the thickness here will only influence the display thickness in the View, not the real thickness of the zone in the model. By default, the value is initially set to the average thickness of the zone in the model.

Average  The average thickness of the zone in the model (read-only).

Maximum  The maximum thickness of the zone in the model (read-only).

Layering type for Zones in Level 1  Here you specify the internal modeling of your highest stratigraphic level, i.e. Level 1 in your 3D Structure Zonation view. The layering options available here are identical to those described in 'Layering Type' above. Changing this setting will also change the layering type indicator in the level before Level 1 in the 3D Structural Zonation view.

Vertical 3D extent  With this option, you can control the vertical extent of the additional top and base layers that the 3D grid creates as a 'buffer' before it starts inserting the input surfaces. By default, 200 m is added to the top and base of the grid. In some cases of steep dipping surfaces this amount of extension is not enough and the surfaces can truncate on the top or base of the 3D grid. In this case, enter a value in the entry field, greater than the default 200 m to extend the grid vertically and create more space between the surface and the top and base of the grid. This allows steep surfaces to be extrapolated without being limited by the vertical extent of the grid. You can select the option Top and Base Layer Visible from the Display Settings that are available in the context menu of the 3D grid, to visualize the vertical extent of the grid.

Surface  

Name  Lists the names of the surfaces to be created in the 3D structural model. The names are adopted from the names of the events that are assigned to the zone boundaries in the Stratigraphic Model.

Representation  Shows the representation of the surfaces in the model and identifies the representation type (tri-mesh, 2D grid, polyline set, point set or marker). Note that tri-mesh, 2D grid and polyline set representations are considered 'dense' data. Marker representations are considered 'sparse' data, as well as point set data when the Point Set is Dense option is not checked. By default, all point set data are set to be treated as dense data.

Construction Sequence  The surfaces in the 3D Structure Zonation View are constructed according to the following sequential order:

This means Geometric Priority is dominant over Stratigraphic Level, which is dominant over the User Priority, which is dominant over the Layering Type (Layering Type is defined on the Zones tab). For an example, see The building sequence of surfaces in the 3D structural model.

There is one exception: unconformities and intrusions that are assigned to a fault model (which is used in the structural model you are constructing) are always constructed first, irrespective of their hierarchical level in the Stratigraphic Model. When they are not assigned to a fault model, they follow the normal sequential order as mentioned above.

Geometric Priority  The Geometric Priority is 1 when the surface representation is 'dense', i.e. a tri-mesh, 2D grid, point set or polyline set. The Geometric Priority is 2 when the surface representation is 'sparse', i.e. a marker or a point set for which the default 'Point Set is Dense' checkbox has been unchecked on the Edit Model form.

The Geometric Priority is the most dominant factor in the surface construction sequence (see sequential order above). Surfaces with Geometric Priority 1 ('dense') are always constructed before surfaces with Geometric Priority 2 ('sparse').

For example, first all 'dense' surfaces at Stratigraphic Level 1 will be constructed. Secondly, all 'dense' surfaces at Stratigraphic Level 2 will be constructed, etc. When all 'dense' surfaces within the 3D Structure Zonation View are constructed, only then the 'sparse' surfaces are constructed, going from Stratigraphic Level 1 to deeper levels, until all surfaces are constructed. See Dense and sparse data within a single event for how the application handles events that have both a 'dense' and 'sparse' data representation.

Stratigraphic Level  This column shows the hierarchical positions of the surface representations in the 3D Structure Zonation View (for information only). It is the second-most dominant factor in the surface construction sequence (see sequential order above). When the Geometric Priority (the most dominant factor) for a group of surface representations is equal, the Stratigraphic Level plays a role, with Level 1 surfaces being constructed before Level 2 surfaces, etc.

User Priority  The User Priority is the third-most dominant factor in the surface construction sequence (see sequential order above). When the Geometric Priority (the most dominant factor) and the Stratigraphic Level (the second-most dominant factor) are identical, this column takes effect. In this column, you can enter the values 1 or 2 (1 is set by default for all surfaces). When entering User Priority 2 for a particular surface, this means that the surface will be constructed after the surfaces which have User Priority 1; as such, you have demoted the surface.

Interpolation  

Quick Settings  Optional column. You can use Quick Settings to fill the Method column with the appropriate interpolation method based on the data representations of your surfaces. Note that a change in the Method column triggers other relevant columns to become active for editing. Upon opening the form, the quick settings are automatically applied; when closing the form, any changes you made will be saved on the form.

Data density: full  Select this option if your underlying data consists of a tri-mesh, 2D grid, point set or a polyline set which covers the complete area (no big holes or gaps occur). Upon selection, the interpolation method in the Method column will be automatically set to 'Ordinary Kriging'. Note that Kriging needs additional parameter settings, i.e. the variogram components such as radii, a direction and the anticipated function.

Data density: sparse  If your underlying data consists of a marker set, a point set that is set to be treated as sparse, or is only described locally in few regions of the area, select this option. Upon selection, the interpolation method in the Method column will be automatically set to 'Distance Weighted'. Note that the column 'Power (Distance Weighted)' becomes available for editing.

Method  Select an interpolation method to construct the surfaces. If you used the Quick Settings column (optional), the Method is already set according to your Quick Settings selection, however, you can always manually overwrite this selection.

Triangulation  This uses the triangulation algorithm to interpolate the surface using the input locations as constraining input. There are no additional parameters required for this method.

Inverse Distance Weighting  This uses the distance-weighted algorithm to interpolate the surface using the input locations as constraining input. The column Power (Distance Weighted) becomes editable which is used as input to this method. The Power is the exponent used for the weighting of the distances. Choose a value between 0.5 and 7.

Ordinary Kriging (Legacy)  This type of Ordinary Kriging does not make use of the industry standard Kriging library and is performance optimized. The values in the Function, Major Range, Minor Range and Azimuth(GN) (and dependent on the function, also Power) columns become editable and are used as input to this method.

Recursive Refinement  This method creates a grid around your input data and assigns values from the data points to the nodes of the grid (snapping) in order to build the output surface. The grid starts with a coarse resolution and it is refined iteratively in order to reach the resolution of the output surface. In the 3D Structural Modeling workflow, the application uses defaults settings for Recursive Refinement to interpolate the surface and for that reason no further settings have to be specified on the Edit Model form. For an overview of the default settings, see the section Parameters > Default settings in the topic Recursive Refinement.

Data Points  Shows how many input points are available, this information is read-only.

Use Trend Analysis  Check the box to enable data filtering and trend analysis to filter spiky or inconsistent input data, and to speed up the interpolation of data sets with a large amount of input points. Trend analysis first uses a relatively coarse, regularly spaced grid in the specified area. The interpolation techniques are used to compute the values at these data points. A relatively fine spaced grid is then filled with the values from the coarse grid adjusted with the local offset of the available data points. The filtering settings will be used to group the input data points into new data points based on the filtering method and the footprint.

Points Trend Analysis  Specification of the number of data points in the coarse, regularly spaced grid of the trend analysis. This information can only be edited if Use Trend Analysis is selected.

Power (Distance Weighted)  Only editable if the Distance Weighted method is selected in the Method column. Displays the value defined for the power parameter for distance weighted operations.

Function  Only editable if the Ordinary Kriging method is selected in the Method column. Select the type of function that describes the underlying variogram model used during Kriging. Choose Exponential, Exponential Power, Gaussian or Spherical.

Major Range  Only editable if the Ordinary Kriging method is selected in the Method column. Specify the major range of influence.

Minor Range  Only editable if the Ordinary Kriging method is selected in the Method column. Specify the minor range of influence.

Azimuth(GN)  Only editable if the Ordinary Kriging method is selected in the Method column. Specify the azimuth (angle with the Northing direction) of the axis corresponding with the major range.

Power  Only editable if the Exponential Power function is selected in the Function column. Specify the power of your exponential power function here.

Construction Settings  

Quick Settings  Optional column; you can select whether you want the surfaces to be fault block aware (Varying across faults), or not (Continuous across faults). Upon selection (press tab on your keyboard to apply the selection) the settings in the Fault Block Aware and the Prevent Horizon Creep columns are automatically updated in correspondence with your selection.

• Varying across faults  The surface for each fault block is interpolated individually, without taking into consideration any information from the other side of the fault. This results in surfaces which are 'fault aware' in which layers can have different thicknesses in different fault blocks. The Fault Block Aware and Prevent Horizon Creep options are toggled on by default when this option is selected.
• Continuous across faults  The interpolation process assumes a continuous surface across faults. The surface will be 'smooth' at the location of a fault.

Fault Block Aware  If you select Varying across faults in the Quick Settings column (optional), this checkbox is automatically checked. When checked, interpolation maps out the surface for each fault block separately. Only the data points within a single, individual fault block are used for surface interpolation of that specific fault block; data points at the other side of the fault are ignored.

Prevent Horizon Creep  If you select Varying across faults in the Quick Settings column (optional), this checkbox is automatically checked. When checked, no surface will be constructed in fault blocks that contain no data, or only contain sparse data (i.e. marker data). An exception to this rule exists for horizons that are stratigraphically situated between other surfaces, which will always be built (the checkbox takes no effect). Note that Prevent Horizon Creep only takes effect when the Fault Block aware checkbox is checked.

Constrain this Surface  Use this option to set a zone to zero thickness field wide at a certain distance away from the input data (e.g. well markers). Beyond that distance, the constrained surface will be collapsed onto the surface above ('Top') or below ('Base'), resulting in zero thickness of the zone in between. At the locations where input data exists (e.g. markers at well locations), this input data is honored, with a smooth transition towards the collapsed region (see 'How the Constrain this surface option works' further below).

Collapsing only occurs in regions without input data points. For example, a surface based on well markers will collapse field wide beyond the distance away from the wells, as no data points exist in those areas. When you apply the ‘Constrain this Surface’ option to 2D grid input data, no collapsing takes place at all those locations where 2D grid input data exists (which might be almost the entire field area). Therefore, the most common use case of this option is for surfaces based on markers.

Note that:

• The hierarchy of the building sequence controls to which surface your surface will be collapsed; if that surface has not yet been constructed in the building hierarchy, the surface will collapse to the next existing surface. For more information on the building hierarchy, see The building sequence of surfaces in the 3D structural model.
• If you want to enforce a zero thickness zone at particular well locations (as opposed to field wide), use the ‘constraint marker’ option, explained in Setting the zone thickness to zero by constraining a surface .

Using the 'Constrain this Surface' option, you do not need to specify individual well marker constraints.

Distance  Only active when the Constrain this Surface checkbox is checked. Specify a distance to influence the lateral constraints. The next paragraph 'How the Constrain this surface works' explains how the 'Distance' is defined.