3-D Parameterization of the Geological Space: The GeoChron Model
Moyen, Remi, Jean-Laurent Mallet, Tobias Frank, École Nationale Supérieure de Géologie, INPL/CRPG, Nancy, France
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.