Building and Editing a Sealed Geological Model

Abstract

In Solid Modeling, a boundary representation (b-rep) defines solids by their bounding surfaces, providing an efficient volume description. Building on this representation, we present the notion of a Sealed Geological Model. In such a model, the geological surfaces define a partition of the domain of interest into regions; analytic functions can be defined in these regions to describe the spatial variations of the subsurface properties. Such descriptions can be used in Geophysics, 3D GIS, and for discretization purposes. In addition to the b-rep representational validity conditions, Sealed Geological Models must satisfy conditions of geological consistency. Bearing these conditions in mind, we describe a methodology to create and modify the shape of such sealed models interactively. We use the hierarchical relationship between geological surfaces to help reshape the contact between a fixed surface (a surface that other surfaces can slide along, such as a fault, erosion surface, or salt top) and a secondary deformable surface (e.g. horizon, older fault). Although designed to meet the demanding requirements of interactive model editing, our methodology could also make use of displacement vectors computed by an automatic process such as tomographic inversion or 3D balanced unfolding.

KINE3D: a New 3d Restoration Method Based on a Mixed Approach Linking Geometry and Geomechanics

“…These objects and their borders have various topologies: for example, they can be either closed or open. Building such structural models is a crucial research topic and numerous techniques have been proposed so far (one can for example refer to Caumon et al 2003). In the following, they will be considered as an input.…”

“…Thus, as a post-processing, nodes are split along main faults and horizons. This can be done efficiently, using topological considerations only (see Caumon et al 2003 for the analogous 2D problem). This information will also be useful for defining material regions (groups of connected tetrahedra) or setting boundary conditions, where one has to identify nodes lying on a given fault or a given horizon.…”

Surface-Based 3D Modeling of Geological Structures

“…This means, for instance, that a fault surface needs not be cut along horizon tear lines, which makes model updating much easier when new data becomes available. Naturally, specific conditions depending on the type of geological interfaces can also be stated (Caumon et al 2004). The rock unit non-intersection rule states that for any two rock boundaries H i and H j , H i may lie on one side only of H j , and conversely.…”

“…For instance, a fault tear line on a horizon consists of two logical borders for the hanging wall and footwall. From this definition, the free border rule states that only fault surfaces may have logical borders not connected onto other structural model interfaces (Caumon et al 2004). Indeed, stratigraphic surfaces necessarily terminate onto faults, unconformities or model boundaries (Fig.…”

“…This extrapolation does not necessarily mean that meshes along the contact are coincident. Therefore additional processing may be needed to obtain a sealed contact (Caumon et al 2004;Euler et al 1998). …”