Nevertheless, the user can manage unconformities with polarity changes by disabling the "polarity consistency" option in the Properties of the model grid
The preview is done using a couple of constraints around the yellow seed, meanwhile the real geomodel uses all the constraints present in the entire grid.
III. What is the difference between horizons coming from the Model-Grid and horizons coming from the Horizon Stack?
The horizons coming from the Model-Grid are seismically consistent and present where there are data. In the case of erosion or non-deposition, the horizon will not be mapped. It is geologically consistent.
The horizons coming from the Horizon Stack are modelled through the Geo-Model, meaning they are smoother, covering the entire survey, even in the case of erosion or non-deposition, and following the trend of the seismic. They are no longer seismically consistent.
Not necessarily, even if there is a gap in the marked horizons, by increasing the interpolation parameter for the Geo-Model Creation, PaleoScan will fill the gaps and the Horizon Stack will be complete (if the Interpolation Size is high enough).
To rename a horizon from the Model-Grid, the user has to open the Horizon List, right click on the name and select the option Rename.
The horizon can also be selected (F keyboard shortcut) by double clicking on the horizon in the Model-Grid (the horizon turns red), it can then be named from the Properties window.
Having gaps in the preview does not mean having a lack of nodes, it just means that the nodes inside the gaps are not linked to the rest of the Model-Grid. To address this issue, the user needs to connect nodes inside the gaps to nodes outside the gaps (i.e. where there is a preview).
If there is a gap in the preview that the user cannot fill, increasing the interpolation parameter in the Geo-Model Creation window will help fill the gaps in order to have a complete Geo-Model.
To refine the grid, the user needs to be in cross navigation mouse mode (G shortcut). They then need to place the seed on a specific event and press W to activate the chosen event. Next, they have to place the yellow seed on the belonging event and press W again, PaleoScan will connect both horizon patches. This action can be repeated as many times as needed to extend the current horizon as desired.
Once the user is done with the horizon refinement, they can click on the space bar to validate or on M to mark the event.
It is possible. To do this the user needs to open the Model-Grid and click on the Grid Constraints and then Model-Grid Constraint icon and follow the workflow.
The user needs to make sure to start from the Initial Grid (and not the AutoInterp). This ensures that the constraint from the horizons will be applied to a "blank canvas", and that there will not be any conflict.
They need to add the horizons to be used as constraints for the Initial Grid using the Horizon Constraint button.
Finally, they have to re-run an auto-interpretation using the Automatic Propagation button in order to take into account the horizon inserted as constraints.
To save or extract a specific horizon the user needs to mark the horizon, then select it using the Selection Mode (F shortcut) and click on the blue floppy disk in the top toolbar or use the keyboard shortcut CTRL+S.
The grid can be generated between two horizons, or from the top/bottom of the seismic to the key horizon. The option is available in the Advanced Options of the Model-Grid Creation tool.
The input horizons need to be continuous where the Model-Grid is to be generated: no node will be computed between a hole (=void) and a surface, or a hole (=void) and another hole (=void). The Propagate/Interpolate tool available from the Horizon toolbar can be used to fill existing gaps or to generate full surfaces from a picked horizon.
In order to properly interpret and model the stratigraphic level of interest, it is strongly advised to shift both the upper and lower boundaries of +/- 100 to 300ms. This preliminary data conditioning can be done using the Vertical Shift tool available from the Horizon toolbar.
A cropped seismic volume can also be created. Using the Extraction tools available from the Volume toolbar, the user can create an extraction area and then extract this sub volume from the original one. The Model-Grid can then be created on this cropped volume.
Yes, to re-edit a marked horizon, the user needs to activate the cross-navigation mouse mode (G shortcut), put the seed on the marked horizon and press W. The horizon can then be edited as desired.
In the Advanced Options of the Model-Grid creation tool, an Exclusion Zone(s) parameter allows the user to drop objects (layers, geobodies and Multi-Z) so that PaleoScan will not create nodes inside those objects.
XIV. When I display the model grid nodes on a section, the nodes are not always located on a seismic event, why is that?
The nodes display is a projection when the seismic section is not located exactly at the centre of the patch. Therefore, the nodes might be slightly shifted compared to the seismic events. The patches, which define the horizons, will follow the seismic events anyway.
The user needs to click on the Update button at the bottom of the horizon list to refresh it. The marked horizons will appear with a M
If faults and/or exclusion zones were used for the Model-Grid generation, there will be voids at the location of the faults/exclusion zones. This is quite useful if the user does not want to generate the grid around salt domes for instance. If the user wants to have nodes at these locations, they must not use the faults/exclusion zones option.
A marked horizon is a horizon that the user decides to highlight using the M keyboard shortcut. It is displayed in colour. However, it is not a saved horizon. Horizons that are not marked are also taken into account and validated by pressing the Space bar. All horizons, marked and not marked, will be used to calculate the Geo-Model.
The global interpretation needs to be saved using the top bar of the Model-Grid window or the Save Interpretation button of the Model-Grid toolbar.