LOCACE Program: A New Tool for Balancing Cross Section

I. Moretti, F. Bessis, B. Colletta, T. Cuvillier, M. Larrere, S. Triboulet, J. Letouzey, V. Maisondieu, P. Werner

LOCACE is an interactive system designed to test the geometrical coherence of a depth-converted seismic section. The approach is to restore the geological layers in their initial deposit positions. If this restoration is possible, the hypothesized interpretation may be correct. If the restoration is impossible or unrealistic, the interpretation will be wrong.

Basically, the restoration process assumes the layer's surface is conserved during deformation. It can also assume a given surface variation, for instance, when there is compaction due to sediment burying. Different models of deformation can be applied, depending on the geologic context: conservation of both length and thickness (Kink method) for constant-thickness layers, or conservation of length and thickness ratio or conservation of thickness and length ratio for nonuniform sequences.

To obtain a meaningful result, a cross section processed with LOCACE must be in the direction of the tectonic displacement. The tectonic style can be extensive or compressive. LOCACE does not provide the correct interpretation, rather it tests the geometric soundness of the geologist hypotheses. Graphical editing allows one to modify the representation of any section during the testing process. The deformation models can be applied backward or forward in time.

The balancing of the initial cross section implies some geometric modifications. The seismic coherence of this interpretation is checked with a ray-tracing program. This trial-and-error process can be interacted.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.