Abstract: Precaspian Basin: Vanishing Salt

KLARNER, SABINE, MATTHIAS KOERBE, and PAUL KRAJEWSKI

Traditionally zones of non- or poor reflectivity in seismic sections have been used to document the presence of massive Permian age salt diapirs in the eastern part of the Precaspian Basin.

Experience from the salt bearing Northern German Basin gained during the last decade offers an alternative model for the Precaspian Basin. In Northern Germany, the apparent volume of salt in the seismic section decreases proportionally to the improvement of processing techniques applied.

Reprocessing of preexisting Kazakh data using these processing experiences resulted in considerable improvement in the coherency of the seismic events. The enhanced seismic resolution yields a new interpretation for the salt flanks and salt overhangs. The optimized processing sequence includes but is not restricted to surface consistent deconvolution, use of dip moveout, detailed velocity analysis, steep dip migration and preservation of amplitude characteristics. Prestack depth migration of representative seismic sections has led to better definitions of the amount and shape of the salt.

Interpretation of reprocessed Kazakhian seismic data as well as new data acquired by Preussag Energie provides very little evidence for large salt bodies. Instead the seismic data support a model consisting of a certain number of large salt overhangs with narrow roots. In many cases towards the basin center the salt stem has vanished. It is replaced by secondary welds between rim syncline complexes. Several of the overhangs are connected by "salt bridges". The "salt bridges" represent the remnants of the former pierced salt walls.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria