The Vienna Basin
Gerhard Arzmüller, Štěpán Buchta, Eduard Ralbovský, Godfrid Wessely, 2006. "The Vienna Basin", The Carpathians and Their Foreland: Geology and Hydrocarbon Resources, Jan Golonka, Frank J. Picha
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Through conventional geoscientific research, a fundamental knowledge of the Vienna basin was acquired with the limited data available at the time. Since then, vast exploration programs of the Austrian, Czech, and Slovakian oil industries have contributed significantly to a more detailed understanding of the geological evolution of the basin.
The pull-apart or piggyback nature of the basin at present is well understood and commonly accepted. Basically, it resulted from an easterly directed extrusion of the Central Alpine block alternating with compressional events during the final stages of the Alpine convergent phase.
The basin evolved in several stages that finally resulted in an intricate arrangement of prominent highs and partly deeper subsided depocenters. The basin was filled by Miocene to Pleistocene sediments that can be subdivided into sequences separated by unconformities; the most pronounced are between the early and the middle Miocene.
The basin-floor section below the Neogene fill consists of the Alpine-Carpathian imbricated system. From north to south, these individual thrust piles are the Waschberg-Zdanice zone, the Flysch zone, the Calcareous Alps (including its Paleozoic base, the Grauwacken zone), the Central Alps, and the Tatrides. All these units lie on top of the Miocene Molasse, a Mesozoic series, and the crystalline basement. This section is well known from wells drilled in the molasse zone sensu stricto but were also drilled in the Vienna basin. Ultradeep wells targeting the autochthonous basement reached total depths of between 6.3 and 8.5 km (3.9 and 5.3 mi).
Oil and gas are trapped in all units of the basin, from the Neogene fill down to the autochthonous sedimentary cover. Generally, the traps are structural, but recently, stratigraphic traps have also been drilled successfully.
The main source rocks are autochthonous Jurassic marls, which seem to form a substantially thickening package in an easterly direction, according to the sporadic well information available. Although the ultradeep well program was believed to be uneconomic at that time, indications point to an unconventional tight-gas play type in the autochthonous Jurassic marls.
The contribution of all Vienna basin member countries made it possible to present a comprehensive surface and subsurface compilation. A cross section through the deepest known part of the basin without border limitations was an additional result of this cooperative effort.