Consideration and algorithm for the construction of XY orthogonal truncated grids.

Jeremy Ruiu and Guillaume Caumon and Romain Merland and Nicolas Cherpeau and Per Arne Slotte. ( 2011 )
in: Proc. 31st Gocad Meeting, Nancy

Abstract

The creation of accurate grids is a key issue in geomodeling. In order to capture the geometric shapes of the objects to model, separate XY orthogonal truncated reservoir grids are created in each fault block and their cells are trimmed by the fault. Those grids may have different resolutions, and have to be merged to create one simulation grid compatible with standard formats. We propose algorithms to cut, truncate and connect such grids in a sealed geological model. The intersection of each grid with the surfaces bounding each region is first computed. To determine the shape of the truncated cells, the trace of the grid on the fault surface is computed as a set of polygons representing the trimmed faces of each truncated cell. These polygons are associated with the corresponding cells in the grid and are used to determine the shape of the other faces of truncated cells. During this step, cell volumes and face areas on the faults, necessary for transmissibility calculation are updated. The connection of neighboring grids requires the computation of common faces on faults surfaces. On the surfaces are used to set transmissibilities with a Non-Neighbor Connections approach. For this, the intersection between the polygons in contact on each side of the fault is computed in order to determine the flow surfaces between the cells of the two grids. Areas are used to set transmissibilities across the fault using non-neighbor connections. The issue of avoiding grid cells with small volumes has to be considered because the presence of such cells may seriousely degrade the performance of the flow simulations.

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BibTeX Reference

@INPROCEEDINGS{RuiuGM2011,
    author = { Ruiu, Jeremy and Caumon, Guillaume and Merland, Romain and Cherpeau, Nicolas and Slotte, Per Arne },
     title = { Consideration and algorithm for the construction of XY orthogonal truncated grids. },
 booktitle = { Proc. 31st Gocad Meeting, Nancy },
      year = { 2011 },
  abstract = { The creation of accurate grids is a key issue in geomodeling. In order to capture the geometric shapes of the objects to model, separate XY orthogonal truncated reservoir grids are created in each fault block and their cells are trimmed by the fault. Those grids may have different resolutions, and have to be merged to create one simulation grid compatible with standard formats.
We propose algorithms to cut, truncate and connect such grids in a sealed geological model. The intersection of each grid with the surfaces bounding each region is first computed. To determine the shape of the truncated cells, the trace of the grid on the fault surface is computed as a set of polygons representing the trimmed faces of each truncated cell. These polygons are associated with the corresponding cells in the grid and are used to determine the shape of the other faces of truncated cells. During this step, cell volumes and face areas on the faults, necessary for transmissibility calculation are updated.
The connection of neighboring grids requires the computation of common faces on faults surfaces. On the surfaces are used to set transmissibilities with a Non-Neighbor Connections approach. For this, the intersection between the polygons in contact on each side of the fault is computed in order to determine the flow surfaces between the cells of the two grids. Areas are used to set transmissibilities across the fault using non-neighbor connections. The issue of avoiding grid cells with small volumes has to be considered because the presence of such cells may seriousely degrade the performance of the flow simulations. }
}