Karst conduit generation: how to constrain ODSIM with geological knowledge?

in: Proc. 32nd Gocad Meeting, Nancy

Abstract

ODSIM (Object-Distance Simulation Method) can be used to model geological underground structures due to late processes such as karstic conduits. At drain scale, karstic conduits are elongated along weakness planes such as lithostratigraphic horizons, bedding planes, fractures or faults, and/or tend to reach the water level. However, ODSIM is based on a perturbed Euclidean distance field which models cylindrical-like 3D envelopes. This work presents different improvements of ODSIM for simulating more realistic shapes. Firstly, we propose using a custom distance property created with a fast marching method. Considering the “velocity” field to be proportional to the hydraulic conductivity allows to stretch the resulting features along the weakness planes. Secondly, to handle specific shapes due to the proximity of the water level, such as trenches or notches, we suggest to impose areas of higher velocity between the skeleton and the water level. Finally we generate a custom random threshold with several variograms and/or distributions following the different features integrated in the “velocity” field. Applied on different models, it is shown that the resulting karst conduits have more realistic shapes than those obtained with the previous workflow, while the variability of structures that can be modelled with ODSIM is preserved.

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BibTeX Reference

@INPROCEEDINGS{,
    author = { Rongier, Guillaume and Collon, Pauline },
     title = { Karst conduit generation: how to constrain ODSIM with geological knowledge? },
     month = { "sep" },
 booktitle = { Proc. 32nd Gocad Meeting },
      year = { 2012 },
  location = { Nancy },
  abstract = { ODSIM (Object-Distance Simulation Method) can be used to model geological underground
structures due to late processes such as karstic conduits. At drain scale, karstic conduits are
elongated along weakness planes such as lithostratigraphic horizons, bedding planes, fractures or
faults, and/or tend to reach the water level. However, ODSIM is based on a perturbed Euclidean
distance field which models cylindrical-like 3D envelopes. This work presents different improvements
of ODSIM for simulating more realistic shapes. Firstly, we propose using a custom distance property
created with a fast marching method. Considering the “velocity” field to be proportional to the
hydraulic conductivity allows to stretch the resulting features along the weakness planes. Secondly,
to handle specific shapes due to the proximity of the water level, such as trenches or notches,
we suggest to impose areas of higher velocity between the skeleton and the water level. Finally
we generate a custom random threshold with several variograms and/or distributions following the
different features integrated in the “velocity” field. Applied on different models, it is shown that the
resulting karst conduits have more realistic shapes than those obtained with the previous workflow,
while the variability of structures that can be modelled with ODSIM is preserved. }
}