Sophie Viseur

Stratigraphic well correlations for 3-D static modeling of carbonate reservoirs

The principles and purposes of stratigraphic well correlation in carbonate sedimentary systems are defined and discussed within the context of static reservoir modeling. The challenge of well correlations is to relate the heterogeneities measured at core and well scales to the spatial heterogeneities at reservoir and flow unit scales. The introduction of a priori knowledge in the process of stratigraphic well correlation is critical to support the stratigraphic rules and to establish a coherent geological and petrophysical concept. The links between well correlation and geostatistics are discussed with regard to the stationarity hypothesis and property trend analysis. We stress that wells are incomplete and biased samples of the geological reality, which is not dependent, unlike the dynamic reservoir behavior, on the well numbers, location, and spacing. Stratigraphic rules are applied as a function of the well spacing relative to the geological reality. A simple trigonometric method, combining angle of base profile, paleobathymetry, and well spacing, is introduced to check the validity of the well correlation in carbonate ramp-like systems. Two models, based respectively on outcrop and subsurface with seismic data, are discussed in detail to show the combined influence of the data set, sedimentary systems, and diagenetic transformations on stratigraphic well correlations.

3D Feature Line Detection Based on Vertex Labeling and 2D Skeletonization

In this paper, we present an approach to extract feature lines on a 3D mesh. The main problem of classical methods is the difficulty to obtain connectivity of resulting lines. In order to sort out this recurrent problem, we propose an algorithm based on the following ideas. The first one is to label candidate points: they characterize the relevant areas corresponding to the expected features. Our second idea is to unfold this binary flagged mesh into a 2D space in order to use well-known morphological operators. By mapping the resulting output back on the mesh, we get relevant and connected feature lines. We then apply this technique to geological data scans to extract fractures and bench limits.

Geological map of the Middle Triassic Latemar platform (Western Dolomites, Northern Italy)

The Latemar is a Middle Triassic isolated carbonate buildup with a diameter of approximately 3 km, that crops out in the western Dolomites, northern Italy. The platform is an important case study and potential analogue for carbonate hydrocarbon reservoirs. Detailed field mapping of the platform has been carried out on a high-resolution topographic base extracted from airborne LIDAR to produce a geological map at 1:5000 scale. Remote sensing was used for the recognition of structural features and then validated in the field. In addition, high-resolution digital photographs were used to interpret the geology of inaccessible rock walls. This work represents a up-to-date detailed geologic map of the Middle Triassic Latemar platform that enhances its internal units subdivision and highlights its complex shape, characterized by gulfs and internal basins and strongly controlled by synsedimentary tectonics.

Insights of 3D Geological Modelling in Distributed Hydrogeological Models of Karstic Carbonate Aquifers

Flow simulation in karstic aquifers with distributed hydrogeological models may be used to numerically model the spatial distribution, the connectivity and the geometry of the karstic network. A new approach is proposed to characterize the karstic network and to reproduce it by the use of 3D geological modelling. The observed karstic network is first decomposed into sets of unidirectional elements which are analysed in 3D with variograms in term of dimension and distribution. These sets of karst directions are then stochastically simulated in 3D in a curvilinear grid that is consistent with the orientation of inception horizons. Several probability maps or 3D probability fields can be added as secondary data in order to constrain the distribution and the connectivity of the simulated karstic network.

FEATURE LINE EXTRACTION ON MESHES THROUGH VERTEX MARKING AND 2D TOPOLOGICAL OPERATORS

Classical approaches of feature line detection rely on curvature derivatives. They generally suffer from a common problem: the connectivity is hard to obtain and it is impossible to generate intersections between feature lines. This article presents a method to extract feature lines on 3D meshes. In order to sort out the recurrent issues of traditional approaches, we propose a novel algorithm based on two ideas. First, all the mesh vertices are marked according to the curvature values: a binary map with candidate regions is then constructed. The second idea is to isolate each candidate region and transform it into a line. To achieve this, we parameterize the region into its 2D regular representation. We then perform a skeletonization to obtain lines with high connectivity. By applying the inverse parameterization, the feature lines are mapped back onto the 3D mesh. In the end, we extract perceptual salient parts and above all connected feature lines. In order to evaluate and validate our algorithm, we compare our method to classical ones and apply our technique to a geological context.