Equilibrage de structures géologiques dans le cadre du projet Gocad

Philippe Samson. ( 1996 )
Institut National Polytechnique de Lorraine

Abstract

Balancing 3D geological structures allows to validate a structural model by analyzing its geometrical evolution through time. Balancing theory is based on volume preservation. This is a 3D concept that can therefore be better handled in 3D than with classical 2D cross-section approaches. However being in 3D introduces sorne difficulties. First of ali, one has to generate a 3D initial model. We solved this problem by using gOcad. Since gOcad surfaces are based on discrete triangles, complex models can easily be generated. We developed algorithms to adapt the mesh to the problem for which the model has been created (unfolding for example). Since a 3D surface is not necessarily unfoldable, we propose a preliminary curvature analysis that gives key information for unfolding, folds organization and faults interpretation. We propose an algorithm for preserving the surface area while flattening it. Considering that the goal is to unfold a full 3D model, we combine volumetrie preservation algorithms with the area preservation for the surfaces. We propose, as weil, a simple shearing method. Another application of simple shearing is flattening of a model, allowing sedimentologists to generate facies correlations · between wells while accounting for the structural model. Given that a 3D model can be divided in severa! blocks limited by faults, the rigid blocks fitting method reestablishes consistency between the blocks that were unfolded independently. With these methods, a geologist can unfold a full 3D model and check his assumptions regarding the current geometry of the structure and the deformation path.

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BibTeX Reference

@PHDTHESIS{Samson1996a,
    author = { Samson, Philippe },
     title = { Equilibrage de structures géologiques dans le cadre du projet Gocad },
      year = { 1996 },
    school = { Institut National Polytechnique de Lorraine },
  abstract = { Balancing 3D geological structures allows to validate a structural model by analyzing its geometrical
evolution through time. Balancing theory is based on volume preservation. This is a 3D
concept that can therefore be better handled in 3D than with classical 2D cross-section
approaches. However being in 3D introduces sorne difficulties. First of ali, one has to generate a
3D initial model. We solved this problem by using gOcad. Since gOcad surfaces are based on
discrete triangles, complex models can easily be generated. We developed algorithms to adapt
the mesh to the problem for which the model has been created (unfolding for example). Since a
3D surface is not necessarily unfoldable, we propose a preliminary curvature analysis that gives
key information for unfolding, folds organization and faults interpretation. We propose an algorithm
for preserving the surface area while flattening it. Considering that the goal is to unfold a
full 3D model, we combine volumetrie preservation algorithms with the area preservation for
the surfaces. We propose, as weil, a simple shearing method. Another application of simple
shearing is flattening of a model, allowing sedimentologists to generate facies correlations ·
between wells while accounting for the structural model. Given that a 3D model can be divided
in severa! blocks limited by faults, the rigid blocks fitting method reestablishes consistency
between the blocks that were unfolded independently. With these methods, a geologist can
unfold a full 3D model and check his assumptions regarding the current geometry of the structure
and the deformation path. }
}