Discrete fracture modeling for fractured reservoirs using Voronoi grid blocks
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Date
2007-09-17
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Texas A&M University
Abstract
Fractured reservoirs are commonly simulated using the Dual Porosity model, but
for many major fields, the model does not match field results. For these cases, it is
necessary to perform a more complex simulation including either individual fractures or
pseudofracture groups modeled in their own grid blocks.
Discrete Fracture Modeling (DFN) is still a relatively new field, and most
research on it up to this point has been done with Delaunay tessellations. This research
investigates an alternative approach using Voronoi diagrams, yet applying the same
DFN principles outlined in previous works.
Through the careful positioning of node points, a grid of Voronoi polygons can
be produced so that block boundaries fall along the fractures, allowing us to use the DFN
simulation methods as proposed in the literature. Using Voronoi diagrams allows us to
use far fewer polygons than the Delaunay approach, and also allows us to perfectly align
flow so as to eliminate grid alignment errors that plagued previous static systems. The
nature of the Voronoi polygon further allows us to simplify permeability calculations
due to orthogonality and, by extension, is more accurate than the commonly used cornerpoint
formulation for non-square grid blocks.
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Keywords
fractured, modeling, voronoi