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

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 Jaszsag Basin to the Northern Bekes 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 2,000 - 3,000 m and is underlain by Mesozoic-Paleozoic basement belonging to the Mec sek 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 (Jaszsag Basin) part subsided earlier and faster while the southern Bekes Basin section subsided later and finally became deeper than the northern basin side. The delta system, step by step, prograded from northwest towards the southeast, gradually filling up the accommodation space. Concluding the results, the source rocks of the Jaszsag Basin became matured and generated hydrocarbons (between 6.8 and 5.3 Ma) earlier than in the Northern Bekes 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 occasionally sidelong. Recently the migrating gas reaches the base of the Quaternary sediments in the Jaszsag Basin while it is still in the Ujfalu Sandstones in the Northern Bekes Basin. Gas is mainly dispersed; accumulations might have been developing in possible stratigraphic and structural traps.