There are two ways to depth convert fault sticks in Kingdom: you can either generate a velocity volume with VelPAK and use it for depth converting surfaces in 2d3dPAK, or you can directly depth convert the fault sticks in VelPAK.
Using VelPAK Profiles
When depth converting fault sticks, you need to use VelPAK profiles, which work with horizons and faults rather than grids. Before we go over the specific steps, it’s important to note that it’s generally considered best practice to re-interpret faults on the depth-converted sections rather than using the depth-converted faults. This is because fault sticks are typically under-sampled, which can result in unusual shapes in the depth domain, especially where there are velocity contrasts across grids.
Preparing the Velocity Model
If you’ve created a velocity model with grids, the same model will be used for depth converting both horizons and fault sticks. The depth conversion process works on a line-by-line basis. To start, load the line geometries into VelPAK by selecting ‘File > Open TKS…’ in your existing model. From there, choose the surveys and horizons to import, making sure the import option is set to ‘Merge’. For 3D surveys, set the inline increment to 1 to ensure that all interpretation data is captured (unless your interpretation is done on every 10th inline, in which case specify the start inline with the first interpreted one, then set the increment to 10). Next, specify the horizons that match the grids in the same order and finish the wizard.
Snapping the Profile
Once the data is loaded, open the profile module, and you should see the horizons and any fault sticks picked for that line. Before starting the depth conversion, you’ll need to “snap” the profile, i.e., create a sealed section. Click the ‘Snap’ icon to do this. Snapping can be quick or time-consuming depending on the quality of the interpretation. To speed up the snapping process, use the ‘Snap’ fly-out and set the options under the ‘Expert’ section to ‘Yes’—this allows the software to automatically fix minor issues for quicker snapping, but it’s important to review the final snapped sections for accuracy.
Setting Basement Velocity
Once the profile is snapped, check if any faults intersect the deepest horizon. If they do, you’ll need to set a “basement” velocity to depth convert the bottom of the fault stick. Set the current layer to 32 (“Basement”) and use the ‘Depth’ fly-out to select a depth conversion method. The easiest method is ‘Simple Interval Velocity’ with a constant velocity value, though some users prefer a more advanced method like ‘Hyperbolic Tangent,’ which retains a velocity gradient while keeping velocities within reasonable bounds.
Applying Depth Conversion
After setting the velocity, click the ‘Apply’ button in the ‘Depth’ fly-out to depth convert the horizons and fault sticks. Do this for a couple of lines first, then change the ‘Snap’ fly-out to work on all unsnapped lines. Snap them, and then use the ‘Depth’ fly-out to automatically depth convert the remaining lines. You can use the ‘Display’ fly-out to toggle between time and depth displays and populate the sections with interval or average velocities. If the profile screen is blank, double-check that the domain is correctly set.
To transfer the depth-converted fault sticks into 2d3dPAK, export them using ‘File > Export > Profile Fault > Depth’. On the ‘Filter’ tab, select the ‘velpak_to_geoquest_m7_2d_3d_faults.awk’ filter. The exported faults can then be imported into 2d3dPAK as GeoQuest CardImage 7 format. When importing, be careful with the merge options—it’s a good idea to rename the fault sets for safety.