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Surface-Based Reservoir Modelling: Concepts and Application to Carbonate Reservoirs

Gary J. Hampson, Matthew D. Jackson, Peter J. R. Fitch, and Cédric M. John
Department of Earth Science and Engineering, Imperial College London, UK

We present a surface-based approach to constructing models of carbonate reservoirs. In this approach, all geologic heterogeneity, whether structural, stratigraphic, sedimentologic or diagenetic, that impacts on the spatial distribution of petrophysical properties is modelled as one or more discrete volumes bounded by surfaces. The modelled surfaces can be deterministically interpolated between control lines or points, or incorporate a stochastic element where control data are sparse. Models constructed from surfaces are not constrained by an underlying grid; indeed, the model is generated without reference to a grid. The only difference between ‘geologic’ and ‘simulation’ models is that the latter incorporates a grid (or mesh) to allow numerical solution of the governing flow equations, with the grid architecture driven by the architecture of the modelled surfaces. The construction of a grid around surfaces that describe geologic heterogeneity results in more accurate and efficient capture of complex heteroegenity geometries and distributions, relative to current modelling practice of representing most geologic heterogeneity on a pre-defined grid. The surface-based approach to gridding (or meshing) is directly compatible with the next generation of unstructured-mesh simulators, and allows the capabilities of the latter to be utilised fully in the modelling of complex reservoir architectures. A surface-based approach to model construction may facilitate a step change in reservoir modelling capabilities, since once the requirement to upscale geologic models to a structured simulation grid is removed, there is no need to build geologic models that are restricted by grid resolution. The application of the surface-based modelling approach to carbonate reservoirs has been carried out as part of the ExxonMobil-sponsored Fundamental Controls on Flow in Carbonates academic alliance.

AAPG Search and Discovery Article #120034©2012 AAPG Hedberg Conference Fundamental Controls on Flow in Carbonates, Saint-Cyr Sur Mer, Provence, France, July 8-13, 2012