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Anna Stromback1, John Howell1

(1) University of Liverpool, Liverpool, United Kingdom

ABSTRACT: Supersurfaces, Preserved Dune Topography And Soft Sediment Deformation in the Rotliegend reservoirs of the Previous HitNorthNext Hit Previous HitSeaNext Hit

The predominantly eolian Leman Sandstone is the main gas reservoir in the Southern Previous HitNorthNext Hit Previous HitSeaNext Hit. The upper part of the Leman Sandstone is the liquefied and soft sediment deformed Weissliegend facies that were formed when the erg catastropically flooded by the Zechstein Previous HitSeaNext Hit. Thickness, distribution and reservoir quality is tradationally difficult to predict within the Weissliegend. Mapping a paleo-horizontal supersurface has reveled a dune topography that was present at the time of the flooding. The distribution of the Weissliegend facies and the overlying Zechstein I carbonates and evaporites display a greater thickness in between the paleo-dune highs. The reservoir character of the Weissliegend facies varies greatly and results from differential diagenesis. This is in part related to the soft sediment deformation and partially due to the proximity of the Weissliegend to the overlying evaporites which provide both a source of fluids and a trap for upwelling fluids.

The Cretaceous Troncoso Sandstone also represents a flooded dune Previous HitfieldNext Hit, overlain by evaporites. This system outcrops in the Neuquen basin in Argentina and has been used an analog. Similar, but smaller scale soft sediment deformation has been observed and a preserved topography underlying carbonates and evaporites. Similarities between the Neuquen and the Southern Previous HitNorthNext Hit Previous HitSeaTop basin are studied and a model to establish varying reservoir properties of deformed eolian facies is presented

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