Tip to prevent a fault from intersecting the boundary

PhamVietThai

I have four seams (Veins) modeled from 2D cross-sections, as shown in the attached image. In my geological model, I’ve introduced two faults: F.A and F.KT4. However, these faults do not intersect all coal seams. Specifically:

• Fault F.A only cuts the upper seam (Vein 1),
• Fault F.KT4 cuts the three lower seams (Veins 2, 3, and 4).

When using the Fault System feature in Leapfrog Geo, the software forces each fault to cut through all seams, which makes the geological model difficult to control and less geologically realistic.

I would like to ask if anyone has tips or workarounds to handle this scenario — for example:

• Creating a “fake” lithology to limit the fault range,
• Using Distance Functions with a very small offset (e.g., 0.001 mm),
• .TEC

I’d really appreciate any suggestions or best practices from your experience, and would love to discuss this further with anyone who has encountered a similar case.

Thanks ALL

ClareBaxter

Hi,

This is a good question as it can be tricky to model in Leapfrog. Do you need both faults to be separate objects in the 'Fault System'?

It appears, both terminate between V1 and V2 seams. I would try joining the two fault surfaces and edit the "fake" part in between to ensure it runs in the lithology volume. This way you still only have two fault blocks to work with and I believe you would be able to keep the same settings for the lithology surfaces and it will give you the output you are looking for.

If you need both fault surfaces to be separate, I do have an idea, however there is a bit more involved in the workaround.

PhamVietThai

Hi Clare,

I'm Thai. Thank you for your suggestion.

I’m aware that Seequent offers a course on finite fault modelling. However, in my assessment, this method is quite complex to apply in my current case. The main challenges stem from the limited number of drillholes in the area, the significant distance between the faults, and the fact that they intersect several unintended veins. These factors make it extremely difficult to control the output volume of the model.

Regarding the statement “both terminate between V1 and V2 seams”, I don’t believe it’s as simple as it sounds. In fact, the two faults are quite far apart. If you look at the section I shared in my previous question, you’ll see there are around five cross-sections between the faults, each spaced approximately 100 meters apart.

You suggested editing a “fake” fault, but doing so would cause the faults to cut through numerous veins. This would require extensive manual surface editing, making it very challenging to manage. You would likely encounter the same issue if you followed a similar modelling approach to mine.

I would really appreciate it if you could elaborate more on the approach you referred to as being “more complex,” so I can better evaluate it.

At the moment, the only approach I can think of is as follows:

1. Create the fault in the Meshes folder
2. Generate Distance Functions from the mesh surfaces, setting the distance very small to avoid creating large volumes (so as not to affect previously estimated resources)
3. Create a new lithology using the Erosions tool (From Surface) and link the surface to the newly created Distance Function
4. Assign this lithology to the younger surfaces group in the Surface Chronology, and activate it

However, a major limitation is that I cannot create very thin thicknesses (e.g., 0.001 mm) in Leapfrog. Extremely thin surfaces tend to generate unwanted triangular “holes,” which negatively affect the accurate representation of the structure I am trying to model.