Summary
We present a new approach for representing wells in coarse-scale reservoir
simulation models. The technique is based on an expanded well model concept
which provides a systematic procedure for the construction of the near-well
grid. The method proceeds by first defining an underlying fine-scale model, in
which the well and any key near-well features such as hydraulic fractures are
fully resolved using an unstructured grid. In the (coarse) simulation model,
the geometry of the grid in the expanded well region, and the associated
"radial" transmissibilities, are determined from the solution of a fine-scale,
single-phase, well-driven flow problem. The coarse-scale transmissibilities
outside of the well region are computed using existing local upscaling
techniques or by applying a new global upscaling procedure. Thus, through use
of near-well flow-based gridding and generalized local grid refinement, this
methodology efficiently incorporates the advantages of highly-resolved
unstructured grid representations of wells into coarse models. The overall
model provided by this technique is compatible with any reservoir simulator
that allows general unstructured cell-to-cell connections (model capabilities,
in terms of flow physics, are defined by the simulator).
The expanded well-modeling approach is applied to challenging 3D problems
involving injection and production in a low-permeability heterogeneous
reservoir, tight-gas production by a hydraulically-fractured well, and
production in a gas-condensate reservoir. In the first two cases, where it is
possible to simulate the fine-grid unstructured model, results using the
expanded well model closely match the reference solutions, while standard
approaches lead to significant error. In the gas-condensate example, which
involves a nine-component compositional model, the reference solution is not
computed, but the solution using the expanded well model is shown to be
physically reasonable while standard coarse-grid solutions show large variation
under grid refinement.
© 2012. Society of Petroleum Engineers
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History
- Original manuscript received:
16 December 2010
- Meeting paper published:
21 February 2011
- Revised manuscript received:
28 March 2012
- Manuscript approved:
4 April 2012
- Published online:
29 November 2012
- Version of record:
6 December 2012
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