3D geomodelling combining implicit surfaces and Voronoi-based remeshing: A case study in the Lorraine Coal Basin (France)

Abstract

International audienceIn this paper we demonstrate how recent geomodelling techniques can be combined and used to build a 3D geological model on a real case study: the former coal mine of Merlebach (France), that is targeted to be exploited for low-temperature geothermal energy production. From geological maps, cross-sections, borehole and mine exploitation data, we build a 3D model in which are identified the rocks and infrastructures having significantly different permeabilities. First, a structural model of the main geological interfaces in our area of interest (2 horizons and 13 faults) is built with classical geomodelling techniques. Then, we propose to model by surfaces the 71 irregularly stacked, very close and very thin, subvertical coal beds. To ease their construction, we use an implicit method which represents 3D surfaces as isovalues of a scalar field defined in a 3D tetrahedral grid of the area. The corresponding triangulated surfaces are remeshed with a recently proposed method based on Voronoi diagrams so that the exploited parts of the coal beds, now filled by sand, can be computed. The 3D surface-based geological model, in which infrastructures can be inserted as piecewise lines, can be volumetrically meshed. It is available for download as supplemental material, as well as a volumetric grid

3D modeling from outcrop data in a salt tectonic context: Example from the Inceyol minibasin, Sivas Basin, Turkey

“…They can be classified in two main strategies (Frank et al, 2007;Caumon et al, 2009;Collon et al, 2015): (1) the classical modeling approaches, also called explicit approaches, which consist of building surfacesgenerally triangulated surfacesthat fit available data; (2) and the more recent implicit approaches that consider geologic interfaces as isovalues of a 3D scalar field f ðx; y; zÞ. They can be classified in two main strategies (Frank et al, 2007;Caumon et al, 2009;Collon et al, 2015): (1) the classical modeling approaches, also called explicit approaches, which consist of building surfacesgenerally triangulated surfacesthat fit available data; (2) and the more recent implicit approaches that consider geologic interfaces as isovalues of a 3D scalar field f ðx; y; zÞ.…”

“…Its principle is to deform an initial surface to minimize the distance between the sur-face and the data points, by the mean of various interpolation methods (Haecker, 1992;Mallet, 1992;Caumon et al, 2009;Kaven et al, 2009;Collon et al, 2015). Its principle is to deform an initial surface to minimize the distance between the sur-face and the data points, by the mean of various interpolation methods (Haecker, 1992;Mallet, 1992;Caumon et al, 2009;Kaven et al, 2009;Collon et al, 2015).…”

“…In such a case, implicit modeling methods have several advantages to coherently build stratigraphic series at once as compared with explicit methods Collon et al, 2015). The traces of the strata on the topography are, however, discontinuous due to vegetation and surface processes (erosion and scree).…”

Implicit Modelling of Geological Structures: A Cartesian Grid Method Handling Discontinuities With Ghost Points

“…There is no a priori knowledge on the expected iso-values . The method approximates theses values during a pre-processing stage on input data which fixes the top and bottom horizons to a chosen value and then spatially interpolates the other horizons values linearly in between [20]. The data weights are generally taken constant between all data but can vary depending on the reliability of the data (e.g., borehole data are generally more reliable than seismic data).…”

Implicit modeling of folds and overprinting deformation

“…Deformation events are modeled successively by locally characterizing the relative orientation of their structural elements (Section 3). This modeling strategy is implemented in the framework of discrete implicit interpolation techniques , Collon-Drouaillet et al, 2015, Frank et al, 2007, Mallet, 2014 through a set of specific numerical constraints (Section 4). The principles of this modeling strategy are illustrated on various examples of increasing complexity (Section 5).…”