Subsidence, Thermal and Maturity History of Late Miocene to Quaternary Formations in the Pannonian Basin

Csizmeg, János ¹; Juhász, Györgyi ²; Milota, Katalin ²; Pogácsás, György ¹
(1)Department of Physical and Applied Geology, Eötvös Loránd University, Budapest, Hungary. (2) MOL Plc., Budapest, Hungary.

Subsidence, thermal and maturity history of Late Miocene (Pannonian s.l.) to Quaternary formations has been simulated along a 70 km long regional seismic profile in the eastern Pannonian Basin (Central Europe), through 2 subbasins (from the Jászság Basin to the Northern Békés Basin) with PetroMod v11 software. Input data were based on facies, sequence- and lithostratigraphic models as well as tectonic interpretation. The studied succession varies between 2000-3000 m and is underlain by Mesozoic-Paleozoic basement belonging to the Mecsek zone of the Tisza megaunit. The hemipelagic Endrod Marl Formation lying above the base Pannonian horizon is considered to be one of the most important source rocks within the Neogene Petroleum System of the Pannonian Basin.

As the first step the paleo-water depth changes and the sediment-water interface temperature changes have been estimated. A thermal history model was constructed for the studied regional profile based on published geothermal data, tectonic, kinematic and geodynamic models, organic geochemistry data. Based on the results of the above mentioned models maturity history, migration and accumulation scenarios have been simulated using three different kinetic models. The subsidence was not uniform along the 70 km long profile. The northern (Jászság Basin) part subsided earlier and faster while the southern Békés Basin section subsided later and finally became deeper than the northern basin side. The prograding delta system step by step prograded from northwest toward southeast gradually filling up the accomodation space.

Concluding the results, the source rocks of the Jászság Basin became matured and generated hydrocarbons (between 6.8 and 5.3 Ma) earlier than in the Northern Békés Basin (from 5.3 Ma). The Endrod Marl has mixed type (III and II) kerogene, 1.8% TOC and 208 mg/g Hydrogen Index, it generated mainly gas. According to the results of the simulation scenarios the gas generally migrated upward and ocassionally sidelong. Recently the migrating gas reaches the base of the Quaternary sediments in the Jászság Basin while it is still in the Újfalu Sandstones in the Northern Békés Basin. Gas is mainly dispersed, accumulations might have been developing in possible stratigraphic and structural trap(s).

The work was supported by MOL Group and the Hungarian Scientific Research Fund (OTKA 60861). Support of this research by IES, a Schlumberger Company via PetroMod university grant program is acknowledged.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.