3-D Parameterization of the Geological Space: The GeoChron Model

Remi Moyen, Jean-Laurent Mallet, and Tobias Frank. École Nationale Supérieure de Géologie, INPL/CRPG, rue du Doyen Marcel Roubault, Nancy, 54500, France, phone: +33 (0)3 83 59 64 84, fax: +33 (0)3 83 59 64 60, moyen@ensg.inpl-nancy.fr

Building a 3D-mesh covering the domain of study is one of the key points in reservoir modeling. This mesh must integrate data from various sources and nature (fault geometry, stratigraphic setting, property data, ...), and must allow for different uses (geostatistics, upscaling, flow simulation, ...).

The common pratice consists in building a "regular structured stratigraphic grid" formed of hexaedral cells whose indexes (i,j,k) can be considered as a sampling of a 3D parametric function (u,v,t). In this function, (u,v) corresponds to curvilinear "paleo-geographic" coordinates tangent to the horizons, and (t), viewed as an analog to the geological age of the terrains, is a sub-vertical curvilinear axis approximately orthogonal to the horizons.

However, the regular aspect of these grids induces geometric and modeling approximations, especially in complex fault networks or folded environments. In this article, we propose to use a new mathematical model, called GeoChron, which uses an unstructured tetraedral mesh and allows the parametric function to be computed whatever the complexity of the fault network and independantly of any structured stratigraphic grid, getting thus rid of most of the mentionned approximations.

The usual geostatistics algoritms relying on the structured nature of the grid, we then present a method allowing classical property modeling algorithms to be used on this unstructured mesh. We also show that, unlike structured grids, this method is totally independant of the algorithms used for property modeling, and can thus be used in any framework.

Advances in Reservoir Modeling I
2005 AAPG International Conference and Exhibition (September 11-14, 2005) Technical Program