Throw Modeling on Unstructured Objects

Rémi Moyen. ( 2005 )
in: 25th gOcad Meeting, ASGA

Abstract

Many applications in geology require knowing the throw vector along faults, as they use it either to represent continuity of materials across faults prior to deformation, or to model the deformation of a layer. The throw can be modelled using the fault lips geometry on horizons, however such a 2D approach is not always accurate. In 3D, the throw is implicitly modelled in the parameterisation underlying the structured stratigraphic grids, but these grids are built with a number of approximations on the fault geometry. Unstructured grids such as tetrahedralised meshes allow overcoming the errors and approximations of stratigraphic grids, but there is currently no solution for easily and automatically building the throw vectors on these meshes. This work proposes a solution to this problem, by extending and improving the 2D throw modelling on triangulated surfaces. This method is based on the definition of horizons as isovalue surfaces of a pseudo geological time parameter, and the automatic extraction of 2D throws on these surfaces, thanks to a topological model of the volume. We then present how the throw vector can be used as a DSI constraint, constraining not only the geometry of the object, but also the continuity of properties across the faults. These constraints are used in the building of a GeoChron model, as an improvement of an initial model. Finally, we show how the GeoChron model can be locally improved by manually editing some of these throws.

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    BibTeX Reference

    @inproceedings{MoyenRM2005,
     abstract = { Many applications in geology require knowing the throw vector along faults, as they use it either to represent continuity of materials across faults prior to deformation, or to model the deformation of a layer. The throw can be modelled using the fault lips geometry on horizons, however such a 2D approach is not always accurate. In 3D, the throw is implicitly modelled in the parameterisation underlying the structured stratigraphic grids, but these grids are built with a number of approximations on the fault geometry. Unstructured grids such as tetrahedralised meshes allow overcoming the errors and approximations of stratigraphic grids, but there is currently no solution for easily and automatically building the throw vectors on these meshes. This work proposes a solution to this problem, by extending and improving the 2D throw modelling on triangulated surfaces. This method is based on the definition of horizons as isovalue surfaces of a pseudo geological time parameter, and the automatic extraction of 2D throws on these surfaces, thanks to a topological model of the volume. We then present how the throw vector can be used as a DSI constraint, constraining not only the geometry of the object, but also the continuity of properties across the faults. These constraints are used in the building of a GeoChron model, as an improvement of an initial model. Finally, we show how the GeoChron model can be locally improved by manually editing some of these throws. },
     author = { Moyen, Rémi },
     booktitle = { 25th gOcad Meeting },
     month = { "june" },
     publisher = { ASGA },
     title = { Throw Modeling on Unstructured Objects },
     year = { 2005 }
    }