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My Geology Is Too Complex for My Grid: Grid-Free Surface-Based Geological Modelling
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 80th EAGE Conference and Exhibition 2018, Jun 2018, Volume 2018, p.1 - 5
Abstract
Building spatially realistic representations of heterogeneity in reservoir models is a challenging task that is limited by predefined pillar or cornerpoint grids. Diverse rock types are ‘averaged’ within grid cells of arbitrary size and shape; continuity of baffles, barriers or high-permeability streaks is often lost; large features are over-resolved and small features are under-resolved or omitted. We present a surface-based modelling workflow using grid-free surfaces that allows creation of geological models without the limitations of predefined grids.
Surface-based modelling uses a boundary-representation approach, modelling all heterogeneity of interest by its bounding surfaces, independent of any grid. Surfaces are modelled using a NURBS description. These surfaces are efficient, and allow fast creation of multiple realizations of geometrically realistic reservoir models. Surfaces are constructed by (1) extruding a cross section along a plan-view trajectory, or (2) using geostatistical models. Surface metadata is created to allow automatic assembly of these individual surfaces into full reservoir models.
We demonstrate this surface-based approach using common elements such as facies belts, clinoforms, channels and concretions, which are combined into reservoir models that preserve realistic geometries. This is applied to a coastal-plain and overlying shoreface succession, analogous to an upper Brent Group reservoir, North Sea (e.g. SPE10-model).