3D fault model example: building faulted domains with the Model Descriptor
This case study shows how GEOREKA builds a faulted 3D geological model, with faults that terminate against each other or cross-cut, using the Model Descriptor to define how domains relate.
Creating a 3D fault model is always complicated and subject to interpretation. In GEOREKA, you define fault blocks as sub-domains, convert each fault surface into a signed distance function or a machine learning classifier, and then use the Model Descriptor to state the relationships and relative ages of the faults. Faults then affect only the units older than them, and each resulting zone is modelled separately.
The challenge
Faults rarely come with a single obvious interpretation. A model has to deal with faults that end at other faults, faults that cut across one another, and normal faults, and each choice changes the zones in between.
Workflow
- Define the fault surfaces. Fault surfaces can come from topography traces, drill core or other sources.
- Convert each fault. Create a signed distance function for each fault, or build a machine learning classifier.
- Describe the relationships. In the Model Descriptor (available from version 4), build fault zones by specifying the relationships between the domains that faults separate, including terminating and cross-cutting faults.
- Set relative ages. The relative age of each fault ensures that a fault affects only older units.
- Model each sub-domain. Model the geology separately in each fault block.
Example
In the worked example, the units that predate faulting are the Post-Conglomerate Andesite and the Sandstone cover. An East fault and a West fault split the model into three zones, and the geology in each sub-domain is modelled separately.
Outcome
The approach makes it efficient to create complex fault zones for sophisticated geological models. Add a measurable outcome here, for example the time taken to build and to update the faulted model.
Apply it
Build faulted models in GEOREKA
Define faults, set their relationships and ages, and model each block in one workflow, with the model updating as data changes. Geological modelling in GEOREKA →
Common questions
Questions
Can GEOREKA model faults that terminate against other faults?
Yes. The Model Descriptor lets you specify terminating and cross-cutting relationships between faults, and their relative ages.
How are fault surfaces defined?
From topography traces, drill core or other sources. Each can be converted into a signed distance function or a machine learning classifier.