C. Galera¹, C. Bennis¹, I. Moretti¹, J. L. Mallet², and J. C. Lecomte¹

¹Institut Français du Pétrole, Rueil Malmaison, France
²Liad-gOcad, Ecole Nationale Supérieure de Géologie, France

ABSTRACT: Unfoldability Versus Incoherences

The construction of a 3D structural model is often based on seismic images more or less precise. In order to validate the model, the geologist usually restores it to check if it looks coherent in its initial state. The first interpretation may be directly unfoldable but also shows areas of incoherence.

The geologist often has doubt about the non-unfoldability which could either be a real structural feature (on ductile layer as shale and salt) or an artefact. Indeed, if parts of the horizons are poorly imaged, the picking uncertainty leads to the horizon containing many little bumps. These local features make the mathematical representation of the horizon not unfoldable.

We present here a new methodology to locally characterize the unfoldability of a surface. It could be used to correct the artefacts in order to obtain a close, smooth and more unfoldable horizon. However, it could also be used to determine the non unfoldable part of a horizon, as, for instance, above a salt diapir or in the hinge of an anticline. The restoration of such a horizon often gives many incoherences with the current software which uses a global approach. Indeed, these software packages, when they are not able to unfold without surface changes, manage to unfold by creating spread distortions which are meaningless from a geological point of view.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado