SCHAEFER, FRAUKE¹, GRIFFITHS, PAUL A.², and OSFIELD, ROBERT^2
1Midland Valley Exploration Ltd, Hannover, Germany
²Midland Valley Exploration Ltd, Glasgow, UK

Abstract: 3D Restoration of Salt Structures: Case Study from the NW German Basin

Three-dimensional restoration of salt structures provides a powerful tool to validate the structural interpretation and geohistory of a given model. Based on the assumption that salt flow at depth generates a response in the sedimentary overburden, the sequential restoration of overburden horizons will reproduce salt flow patterns and overburden basin geometry through time.

Using 3D restoration software, we have carried out a sequential restoration for a diapir located in the NW German basin. The original 3D model was built from the interpreted horizons of eight seismic sections crossing the elongated salt structure. Initially, a passive downbuilding diapir model was adopted for the geohistory framework.

The restoration was achieved by sequentially decompacting, then vertically shearing each overburden horizon to a horizontal datum whilst maintaining the volume of all underlying layers.

The results reveal that there is negligible salt flow throughout Tertiary to Cretaceous times, while major salt flow into the diapir has occurred during Upper Triassic (Keuper) times. The basement fault underneath the diapir has been most active during the Early to Middle Triassic.

Based on the structural development of the overburden through time, the initial geohistory model could be reviewed and replaced by invoking thick skinned extension. Furthermore, areas of uncertainty in the original interpretation are highlighted.

The resulting digital 3D models can be used for further studies, such as hydrocarbon migration analysis for any horizon or time stage required.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas