Upscaling permeability from unstructured meshes to non-matching structured grids. {First} results

in: 2022 {RING} {Meeting}, pages 20, ASGA

Abstract

Numerical models are powerful tools to forecast the behavior of aquifers and subsurface reservoirs. In these numerical models, geological grids approximate the subsurface geometry with structured or unstructured meshes. Because structured grids lead to relatively simple and efficient flow simulation algorithms, they have become the industrial standard to approximate geometries in reservoir modeling. Unstructured grids can produce more accurate geometries of complex geological features and are more flexible to mesh the simulation domain adaptively than Cartesian or Corner Point Grids (CPG). However, explicitly accounting for fine-scale heterogeneity leads to a number of grid cells too large to be directly manageable by flow solvers. Upscaling methods were developed to coarsen geological grids in order to produce manageable grids for flow simulations. Most upscaling methods were developed for structured grids. Here we propose a new upscaling strategy to upscale unstructured grids to non matching structured grids. It combines a control volume finite element (CVFE) method to compute fine scale pressure values and an incremental mesh intersection algorithm to upscale flow information to a non matching coarser structured grid. The intersection algorithm is inspired from computational geometry algorithms. We introduce upscaling methods and present our CVFE solver and mesh intersection algorithm. We apply the upscaling strategy to first geological grids. The obtained results are discussed and first conclusions are then presented.

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BibTeX Reference

@INPROCEEDINGS{zakari_upscaling_2022,
    author = { Zakari, Mustapha and Caumon, Guillaume },
     title = { Upscaling permeability from unstructured meshes to non-matching structured grids. {First} results },
 booktitle = { 2022 {RING} {Meeting} },
      year = { 2022 },
     pages = { 20 },
 publisher = { ASGA },
  abstract = { Numerical models are powerful tools to forecast the behavior of aquifers and subsurface reservoirs. In these numerical models, geological grids approximate the subsurface geometry with structured or unstructured meshes. Because structured grids lead to relatively simple and efficient flow simulation algorithms, they have become the industrial standard to approximate geometries in reservoir modeling. Unstructured grids can produce more accurate geometries of complex geological features and are more flexible to mesh the simulation domain adaptively than Cartesian or Corner Point Grids (CPG). However, explicitly accounting for fine-scale heterogeneity leads to a number of grid cells too large to be directly manageable by flow solvers. Upscaling methods were developed to coarsen geological grids in order to produce manageable grids for flow simulations. Most upscaling methods were developed for structured grids. Here we propose a new upscaling strategy to upscale unstructured grids to non matching structured grids. It combines a control volume finite element (CVFE) method to compute fine scale pressure values and an incremental mesh intersection algorithm to upscale flow information to a non matching coarser structured grid. The intersection algorithm is inspired from computational geometry algorithms. We introduce upscaling methods and present our CVFE solver and mesh intersection algorithm. We apply the upscaling strategy to first geological grids. The obtained results are discussed and first conclusions are then presented. }
}