Faults are highly complex heterogeneous and anisotropic three-dimensional volumes of rock rather than planes, but are generally represented in reservoir models as planar surfaces. Reservoir production data demonstrates that fault zone structure may have an enormous influence on fluid flow. Conventional reservoir modelling tools are unable to capture the influence of fault zones accurately due to its limited functionality. The objectives of this study are to develop 3D upscaled models of sub-resolution fault zone components by means of geometrical upscaling. Geometrical upscaling is the process of calculating across-fault and up-fault transmissibility arising from 3D flow paths through detailed fault zone structure, and representing those transmissibilities into low-resolution upscaled flow simulation model.
In this presentation we describe advances to the existing geometry-based upscaling method, by (a) including fault zone components (e.g. lenses) that are longer than a single grid block, and (b) developing a new flow-based upscaling method to represent more complex and realistic fault zone structures than is possible with the current implementation of the method. In geometrical upscaling, faults are represented into flow simulation models implicitly as neighbour and non-neighbour connection transmissibilities. We build high-resolution flow simulation models of fault zone structure, which we then scale-up using the two methods (geometry-based and flow-based geometrical upscaling) to capture the influences of fault zone geometry.
We assess the accuracy of geometrical upscaling techniques by comparing the sequential flow responses of high-resolution flow simulation models with that of models upscaled in different ways. Our results show that flow-based geometrical upscaling method is a more accurate and easier approach for representing fault zone geometry into flow simulation models than the existing geometry-based approach.
Abstract of talk given to:
57th Irish Geological Research Meeting 2014, UCD, March 2014.