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.

Résumé -Une nouvelle méthode de restauration 3D basée sur une approche couplée géométrie-mécanique -Une nouvelle méthode de restauration 3D a été développée en couplant un logiciel de modélisation géométrique avec un code d'élément fini de mécanique. Cette méthode permet à l'utilisateur d'imposer le déplacement sur le plan de failles afin d'obtenir la géométrie initiale désirée tout en calculant une déformation continue dans les blocs par le programme de mécanique. Le maillage du bloc 3D permet de tenir compte des éventuelles hétérogénéités induites par les couches géologiques et l'évolution latérale des faciès. Les résultats sont discutés dans des cas extensifs et compressifs; en rétro-déformation ainsi qu'en déformation directe. Le cas compressif correspond à la restauration d'un anticlinal faillé constitué de bancs massifs, sable et argile en alternance. Il a aussi été restauré en 2D, via une mise à plat surfacique, et les conclusions des deux restaurations 2 et 3D sont comparées. Le second cas, une modéli-sation directe, est un cas de glissement gravitaire le long d'une marge dans laquelle des chenaux sableux sont interstratifiés dans une matrice argileuse. Les résultats permettent de quantifier la rotation du champ de contraintes sur les interfaces sable/argile. Abstract -KINE3D: a New 3D Restoration Method Based on a Mixed Approach Linking Geometry and Geomechanics -We developed a new methodology for 3D restoration by coupling a geometric modelling software and a mechanical finite-element code. This method allows the geologist to impose the displacement on the main faults in order to

The generation of accurate and reliable unstructured 3D models for reservoir simulation remains a challenge. In this paper, new developments for grid generation, upscaling and streamline simulation for such models are described. In combination, these techniques provide a prototype workflow for the construction of unstructured simulation models. The grid generation framework described here allows the incorporation of both geometrical constraints and grid-resolution targets. Flow adaptation of the unstructured grid (i.e. higher grid density in key regions) is accomplished through the use of single-phase flow calculations on the underlying geocellular grid, which are used to generate target grid resolution maps for the unstructured coarse model. A novel transmissibility upscaling procedure is introduced to capture the effects of fine-scale heterogeneity. A new method for streamline simulation on unstructured grids is also introduced. This technique provides an efficient flow-based diagnostic for the assessment of the coarse simulation model in terms of flow response. The performance of the various components of the methodology is demonstrated using several examples.

A new technology for creating, reliably and automatically, structural models from interpretation data is presented. The main idea behind this technique is to model directly volumes (the geological layers) rather than surfaces (horizons that are bounding these layers). In order to enforce the geological consistency of the created models another key element is built into this technology: it guarantees that the variations of dip and thickness of the created geological layers are minimized, while all seismic and well data are properly honored. The proposed method enables the construction of very complex structural models, independently from the geological settings, and even when such models have to be built from sparse or noisy data. The full automation of the model construction process allows to rapidly update the model, to efficiently identify the most uncertain parameters, to understand their impact, and to iteratively optimize the model until it fits all available data. To demonstrate the advantages of this technique the construction of a complex exploration-scale structural model of a prospect located offshore Australia is detailed.

This paper describes new techniques and algorithms for building consistent and accurate structural models of the subsurface in structurally and stratigraphically complex areas, and proposes an innovative workflow for iteratively building large-scale models in presence of sparse or noisy data. Contrary to traditional 3D modeling approaches, which consist in modeling first geological interfaces independently from each other before gluing them together to form a watertight representation of geological layers, the proposed technique creates first a 3D unstructured mesh representing the volume of interest, which is then sliced and diced by geological horizons and faults. It is based on a global interpolation method in which a scalar property representing the relative stratigraphic age of the formations is interpolated everywhere in the volume of interest. In the process, the geometry of each horizon is effectively constrained by interpretation data of all other horizons belonging to the same conformable sequence. The interpolation is practically insensitive to the complexity of the fault network (X faults, Y faults, thrusts) and yields a high resolution, 3D representation of geological layers, allowing the extraction of main horizons based on seismic input and of closely spaced intermediate horizon surfaces defined by well data. The proposed technique ensures the preservation of four key quality features:Geometrical accuracy: surfaces are as smooth as possible while fitting all input data geometry.Topological correctness: all model contacts are perfect and watertight.Stratigraphic consistency: horizon surfaces cannot cross each other; layering and truncation patterns dictated by the input stratigraphic column are honored everywhere in the model.Structural coherency: variations of fault displacement should be consistent with their size; layer thickness changes should be as regular as possible. These benefits are illustrated through the step-by-step construction and refinement of a large scale geological model located offshore Western Australia. It is also demonstrated that this technique and methodology can successfully be applied to a large variety of structural and stratigraphic contexts. Introduction The standard way of interpreting and modeling subsurface reservoirs establishes a clear separation between the creation of a "container" conforming to the reservoir structure and the interpolation of geological or petrophysical properties. The property population phase commonly leverages comprehensive information from well logs and from the seismic signal, through the use of pre- or post-stack attributes, of quantitative interpretation techniques and of seismic inversion. Conversely, the creation of a structural model traditionally only exploits very limited data interpreted along the main structural or stratigraphic interfaces. There is, however, a much larger amount of structural and stratigraphic information that can be extracted from seismic or log data. Moreover, while traditional workflows are mostly one-way, from the interpretation to the model creation, stratigraphically and structurally consistent models could and should be used to guide the refinement of seismic or well interpretation. This article introduces the building blocks of technology and workflows enabling (1) the incorporation of a vast amount of seismic constraints in structural models and (2) the use of interpolated structural information to iteratively enrich interpretations.