By Sam Bain
The “Split Lithology” tool (available in Leapfrog Geo, Geothermal, and Hydro) creates a new lithology column by sub-dividing lithologies in an imported column. Often simple logging will result in repeating intervals on each drillhole and these will need to be separated for modelling purposes. As an example, perhaps three unique limestone units at different depths are encountered by exploratory drilling. These might all be logged simply as “Limestone”. In this case the splitting tool could be used to divide the “Limestone” intervals into “Upper”, “Middle”, and “Lower” units. Then each unit can be modelled separately. It is important to note that the original logged intervals are preserved, and the new splits are made in a new interval column. The modeller can correct or re-interpret the logging without altering the original field data.
This blog explains how the “Split Lithology” tool works by walking through a simple example.
The “Split Lithologies” function is available by right clicking on an interval table (Figure 1).
The first dialog lets the user name the split lithology and choose a base column (Figure 2). A new split lithology can only use an imported lithology or category column as a base column. Other user created interval columns such as grouped lithologies or interval selections cannot be used as a base column.
The main dialog initially displays the lithologies in the base column (Figure 3). The button beside each lithology indicates which lithology is selected for splitting. By default the first lithology is selected. A new split can only be made from intervals in a single parent lithology. Drillholes displaying the base column are also added to the scene. The visibility of each lithology can be toggled using the eye symbols.
Clicking the “Select Interval” button (A in Figure 3) changes the mouse to interval selection mode. The width of the selection envelope can be changed by left clicking on the first icon in the group labelled B in Figure 3. The number shown in this icon reflects the current width of the selection. The next two icons control whether the mouse function will select or deselect intervals. By default this is set to select (red square on red square). The second option (white on red) is to deselect intervals. This allows correction of selection errors. Clicking the final icon will clear the entire current selection.
Once the desired intervals have been selected, they must be assigned to a new split or an existing lithology. In Figure 4 the highest alluvium intervals in each drillhole have been selected.
After the “Create New Split” option is chosen, you can assign a new split name (Figure 5). In this case the upper intervals have been split into a new unit called “Upper Alluvium”. The colour of the new split can be edited.
The split dialog updates to show the new split below its parent lithology (Figure 6). The drillholes in the scene change to reflect this new interval. Note that the visibility of the new split can be toggled on and off like other lithologies. The new split does not have its own selection button, because it is still regarded as part of the original lithology (Alluvium in this case). This means that if Alluvium is selected, a new split can be made by selecting any intervals from “Alluvium” or the new “Upper Alluvium” intervals. Also, intervals from the new split can be selected individually and assigned back to the original lithology or the entire split can be deleted. Deleting the split will return all intervals to the parent lithology.
As shown in Figure 7, multiple splits can be made from a single lithology. A new “River Channel” split has been made from the “Upper Alluvium” split we made previously . If either new split is deleted then its intervals will be re-assigned to the original “Alluvium” lithology.
As soon as the split is saved a new interval column is added to the interval table, even if no intervals have been assigned to a new split lithology. If new splits have been created then these intervals will have been renamed appropriately and the rest of the interval names will match those in the base column. Like groups, splits may be edited at any stage by double clicking on the split in the project tree.