Hydrocarbon Generation, Migration and Alteration in the Vienna Basin

The discovery of oil and gas, some 150 years ago, has triggered an intensive and extensive hydrocarbon exploration in the Vienna Basin. The oil and gas industry over the years has acquired a quit good understanding of the structure and evolution of the Basin, as well as detecting numerous HC accumulations in nearly all stratigraphic units within the basin.

As soon as the concept of HC-Source rocks become obvious the search for the source rock within the Vienna Basin began, pinpointing the Malmian Mikulov and Falkenstein Formations as the major source rock within the Basin. The majority of the HC-accumulations within the basin are charged from these marlstones.

Despite the conclusive evidences for the Mikulov Fm. to be an active source rock, uncertainty remains about the source rock of the Höflein Gas Condensate reservoir. A long dispute whether or not this reservoir is charged from the Doggerian coaly Gresten Fm. has raged between different authors. Indeed, the Gresten Fm. contains some coal seems as well as bituminous shales.

The first goal of this project is to determine the source rock potential, maturity and the organic geochemical parameters of the Mikulov Fm. and the Gresten Fm in high resolution vertically and laterally. This is followed by a detailed Oil-Source correlation.

After the generation and expulsion of Hydrocarbons from there source rocks, they migrate in pathways towards the surface. During this process some compounds are lost. Knowing their original concentration and the current concentration allows the calculation of migration distances and helps in understanding the migration mechanism (e.g. Migration throw faults or migration throw carrier beds).

The second goal of this project is to establish a migration model

Eventually during migration the Hydrocarbons migrate into sealing structures and become entrapped. Entrapped Hydrocarbons become easily altered by variety of processes. Biodegradation is the one mostly observed in shallow reservoirs although some factors seem to influence the degree of degradation. Another example of an HC-alterating process can be found within deep buried reservoir within the calcareous alps units of the basin. Entraped Oil comes into contact with sulfate rich brines and becomes thermocemical sulfate reduced creating significant amounts of H2S.

The third goal of this project is to gain an understanding of degree and extend of this alterating processes and predict them for future exploration projects.

Cross section through the basin showing the extend and depth of the Mikulov Fm. From Wessely, 1993 in "Erdöl und Erdgas in Österreich" NHM Wien.

 

 

Simplified cross section through the Schoenkirchen reservoir. From Wessely, 1993 in "Erdöl und Erdgas in Österreich" NHM Wien.