3D Grid to Contours

Use the 3D Grid to Contours form (model > Maps & Reports > Contours) to create a surface (2D grid or tri-mesh), project the selected property onto it, and extract polyline contours from this surface. The projection is performed vertically and assigns the maximum encountered property value to each lateral location, creating for example a map of maximum concentration.

This tool can be used, for example, to extract the outline of a CO₂ plume from reservoir simulation results, displayed at a user-selected horizon from the same 3D grid. The form provides additional options to filter by region, select specific time steps or realizations, and define threshold, smoothing and visualization settings for the extracted contour polylines.

3D Grid to Contours supports both JewelSuite's own 3D grid formats (such as JewelGrid) and imported 3D grid formats (such as slanted pillar grid). This enables its use on simulation results originating from external sources.

To extract contour polylines from a 3D grid:

Select a 3D grid and a suitable Property on the 3D grid, for example a CO₂ concentration in a CCS simulation.
On the Settings tab, configure how the property should be projected onto a surface. Any contours extracted later will be positioned on this surface at its corresponding depths.
1. For Projection surface, you can select any stratigraphic surface defined in the 3D Grid, which automatically determines the corresponding K index. Alternatively, you can directly specify a K layer by entering the K index.
2. Enable the Keep discontinuities option to create a tri-mesh projection surface that preserves discontinuities (e.g., fault offsets) still in the surface. This will honor the surface and boundaries better but can create less smooth contours. When disabled, a smoother and continuous 2D grid is created, which may deviate from the original surface in the 3D grid at discontinuities. The preferred option depends on the model and the intended use of the contours. By default, this option is disabled.
  Contour positions will not exactly match between approaches with and without discontinuities, even away from discontinuities, as the mapping process to a tri-mesh and a 2D grid differs.
3. Prefix/Folder is used as a prefix for the projection surface, and as the folder name (in Data in the JewelExplorer) for the extracted polylines when extraction is performed using the Extract Contours form. Providing this name is mandatory.
4. (Optional) You can select a Region property, and specify regions in the Region Selection table. This acts as a filter for which parts of the 3D grid property are included in the projection step. For example, you can choose to include only values from the reservoir section of the grid or only values near a specific wellbore. When None is selected, which is the default setting, the property across the entire 3D grid is used.
When a property with time steps or realizations is selected, the Steps tab allows you to choose which time steps or realizations are projected onto the surface and used for contour extraction. This enables you to create contours only for the intervals of interest. The Step Selection Tools can assist in making this selection. For more information, see Managing time steps and realizations.
On the Extract Contours tab, you can choose to extract contours immediately after projecting the selected property onto a surface.
1. Enable the Extract Contours option to activate the form and extract contours immediately after property projection.
2. Specify a Threshold value at which contours should be extracted. Only positive values are allowed.
  Set the threshold low enough to include all data you want captured within the contour, but high enough to avoid artifacts. For example, if you are interested in values above 0, you would typically choose a threshold close to 0. However, setting it too close can make small mapping artifacts and numerical instabilities have a larger impact, which may introduce unwanted artifacts.
  On the other hand, choosing a threshold that is too high or too low can result in no contour being detected for those values, meaning no contour is extracted. Because the optimal threshold strongly depends on the specific data, there is no single recommended value. It is therefore best to experiment to determine a suitable threshold for your case.
3. The Treat undefined values as setting must be specified so the algorithm knows how to handle undefined values in the source property. It is recommended to choose a value that results in smooth contours without introducing additional artifacts. In many cases, keeping Treat undefined values as at 0 (the default) works well. However, depending on the data type and structure, other values may be more appropriate.
4. You can choose to smooth contours as a post-processing step by de-spiking them. Enable this option by selecting De-spike contours and setting a Gradient threshold, with a default value of 20 degrees. For more details, see the section on the De-spiking polylines tools. By default, smoothing is enabled.
5. Optionally, you can create a CoView with a default framework to display the created contour polylines on a map. This can be used as a starting point for producing high quality maps, for example of a CO₂ plume. This works best when too many contours are not displayed at the same time.
Press Apply or OK to run with the selected settings. Depending on the model size and complexity, this can take a while.

When finished, the projection surface and contour polylines are available in the Data folder in the JewelExplorer (with the defined Prefix/Folder name). If the Create CoView option is selected, it will open automatically and display all created contour polylines. You can retrieve the settings used for contour extraction from the Audit Trail.