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A new approach to upscaling in reservoir modelling
A.O. Onaneye 1 , W.A. Sonibare 2 , D. Mikeš 3
1. Dept of Earth Sciences, Stellenbosch University, South Africa, alfred.onaneye@gmail
2. Dept of Earth Sciences, Stellenbosch University, South Africa, shoniwas@yahoo.com
3. Dept of Earth Sciences, Stellenbosch University, South Africa, mikes@sun.ac.za
ABSTRACT
Why do we need a geological based reservoir model?
Reservoir engineers over the years use upscaling as a tool in simulating reservoir performance and optimizing oil
recovery. Upscaling in concept is all about averaging and replacing a number of heterogeneous fine grids with a
homogenous block. A lot of upscaling procedures have been proposed, but many of them are complex, speculative
and often based on stochastic realizations. Therefore, they lack an approach that is simple and straightforward in
incorporating heterogeneities from the geological record down to the simulation phase.
Hence, we propose an approach that focuses on building our geological model in a fashion that it incorporates
heterogeneities on the one hand and also integrate the geological model into a new upscaling approach on the
other. Reservoir heterogeneities are known to be controlled by the arrangement of various hierarchies of
sedimentary facies and internal bounding surface. To this end, a hierarchical procedure would be a natural way to
build and upscale a geological-based reservoir model in a deterministic manner. In this regard, we initiate a fourstep
upscaling procedure: (1) Model construction: Assignment of flow cells and flow unit, (2) Parameter
assignment: Calculation of capillary pressure and relative permeabilities of laminae, (3) Micro simulation: Steady
state flow simulation on flow cells, and (4) Macro simulation: Assignment of the ensuing effective phase
permeabilities and capillary pressure to the flow units. The flow cell and flow unit are the key elements in this
procedure, while the laminae is the REV (Representative elementary volume) for the flow cell.
Implementation of this new upscaling approach should improve translation of the geological model into
reservoir model, capture necessary geological details and reflect reservoir heterogeneity. This approach lends itself
a simple and straightforward procedure to upscale all scales of heterogeneity for a full field flow prediction and
development plan.
KEYWORDS: Geological model, Reservoir heterogeneities, Upscaling, Reservoir simulation.
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