Abstract
Fine grid geocellular reservoir characterizations often include detailed description of geological and geometric complexity. Since this volume of details can not be handled by commercial reservoir simulators, some degree of coarsening is necessary. The fundamental agenda in coarse grid generation includes development of finer grids in regions with higher flow. Available methods in literature suffer from draw back of inability to consider both the well and geological features which mostly affect the flow response. This study introduces a new method of grid coarsening (flow based) procedure. The procedure encompasses tracing streamline from boundary to the well, monitoring velocity trend along streamline to identify high flow region and selection of appropriate points on streamlines as grid nodes. Differentiating the analytical equation of the streamline path results in developing velocity vectors and adding them up will yield a new term called cumulative velocity. Using this term, the grid points are easily identified which after implementation of Delaunay triangulation and Laplacian smoothing algorithms the main CVFE (Control Volume Finite Element) grid is produced. In addition, a robust up-scaling technique was used to calculate the tensor of permeability.
Flux-continuous finite volume scheme was used to solve the associated flow equation in the coarse block. The generated grid pattern is finer in high flow regions and can successfully adapt itself based on type of geological features presented.
Pressure was the main criteria for comparison the results of this study with those of Cartesian coarse grid. The results indicated that the response of the model with coarse grids (flow based) is more consistent with a fine model. The major advantage of the introduced method is its capability in handling the geological features within the grid. It is worthy to mention that the positioning of the well and adjustment of the required refinements around it are done automatically.
