Summary
Highly detailed geological models, which are primary inputs for reservoir
simulators, necessitate a reduction in the number of gridblocks used in the
solution of flow equations. However, preparing a coarse-scale model that can
mimic the fine-scale behavior is challenging. Cartesian grids suffer from some
shortcomings, such as in adaptation with geological and geometrical features
and the grid-orientation effect that motivates the use of unstructured grids.
Different methods have been used for this purpose, but none is robust enough.
This justifies further research.
In this paper, we propose a novel unstructured-grid-generation scheme that
uses the vorticity of fluid flow in porous media as the determining parameter
for background-grid generation. It entails simulating single-phase flow on the
fine grid and obtaining the velocity field and, subsequently, the vorticity
map. Vorticity is then used to generate the background grid that plays an
essential role in the generation of a desired final coarse grid. At this stage,
users need to determine the value of some parameters, such as maximum and
minimum spacing, vorticity cutoff, and vorticity-intensity degree. The
advancing-front method and Delaunay triangulation are then used to provide the
triangular and Voronoi perpendicular-bisector (PEBI) grid. The developed
technique, which aims to capture both flow and geologic details, produces grids
with higher resolutions at critical vorticity areas, such as around layer
boundaries, and with lower resolution where vorticity is negligible, such as in
homogeneous regions.
This technique is applied to two channelized and heterogeneous models, and
the results are presented. Two-phase-flow simulations are performed on the
generated coarse grids, and the results are compared with those of fine-scale
grid and uniformly generated coarse grids. The results show a greater accuracy
compared with uniformly gridded models.
© 2010. Society of Petroleum Engineers
View full textPDF
(
1,320 KB
)
History
- Original manuscript received:
22 February 2008
- Meeting paper published:
10 June 2008
- Revised manuscript received:
21 September 2009
- Manuscript approved:
24 December 2009
- Published online:
18 June 2010
- Version of record:
2 December 2010
View Cart
