1. New Results of Geological and Geochemical Investigations and Basin Modelling of
the Neogene Sequence, Southern Part of the Great Hungarian Plain, Hungary
1 2
Edina Pável , Viktor Lemberkovics
1
Department of Physical and Applied Geology, Eötvös Loránd University, Budapest, Hungary
2
RAG Kiha Kft., Budapest, Hungary
pavel.edina1@gmail.com
References
Badics, B., Uhrin, A., Vető, I., Bartha, A., Sajgó, Cs, (2011): Medenceközponti földgáz-előfordulás elemzése a Makói-árokban. — Földtani Közlöny, 141, pp. 445-468.
Balázs, E., Nusszer, A. (1987): Magyarország medenceterületeinek kunsági (pannóniai s. str.) emeletbeli vulkanizmusa. — MÁFI Évkönyv, 69, pp. 95-104.
Haas, J., Budai, T., Csontos, L., Fodor, L., Konrád, Gy. (2010): Pre-Cenozoic geological map of Hungary, 1:500 000. — Geological Institute of Hungary, Budapest
Magyar, I., Radivojević, D., Sztanó, O., Synak, R., Ujszászi, K., Pócsik, M. (2013): Progradation of the paleo-Danube shelf margin across the Pannonian Basin during the Late Miocene and
Early Pliocene. — Global and Planetary Change, 103, pp. 168-173.
Pepper, A. S., Corvi, P. J. (1995): Simple kinetic models of petroleum formation: oil and gas generation from kerogen. — Marine and Petroleum Geology, 12/3, 291-319.
Tóth-Makk, Á., (2007): Late Miocene sequence stratigraphy of the Pannonian Basin fill (Kiskunhalas-Mélykút region, Hungary): how core, electric log and seismic data fit together? —
Geologica Carpathica, 58, pp. 353–366.
Acknowledgements
The research was supported by the RAG Kiha
Kft. We would like to express our thanks to
Katalin Lőrincz, Dénes Kisfürjesi, Orsolya Sztanó,
Balázs Badics, Katalin Milota, Lilla Tőkés, Ágnes
Tóth-Makk, Attila Balázs, János Csizmeg and
Enikő Várkonyi. Thanks Schlumberger GmbH for
PetroMod 2012.1 basin modelling software.
Fig.11. Maturity and migration history, potential accumulations of the study area
Pepper and Corvi (1995) TII (B)
Pepper and Corvi (1995) TIIIH (DE)
Pepper and Corvi (1995) TII (B)
Pepper and Corvi (1995) TIIIH (DE)
Pepper and Corvi (1995) TIIIH (DE)
11.6 Ma
9.61 Ma
6.8 Ma
present days
present days
Fig.10. Subsidence history of the study area
16.3 Ma
15.3 Ma
12 Ma
9.61 Ma
7.8 Ma
present days
4. Subsidence history (Fig.10.)
5. Maturity and migration(Fig.11.)
6. Conclusion
The results of the modelling suggest that presently
the Badenian source rock is in the oil generation
zone in the northern and in the northern
part of the southern sub-basin. The oil generation
and migration started from around 6.8 MY. The oil
migrated upward along faults until the Szolnok
Sandstone Formation but accumulations could not
be formed yet. In the southern sub-basin significant
part of the lower and middle Karpatian source rocks
is in the gas generation zone, moreover the deepest
parts of them reached the overmature zone. The
hydrocarbon migration from the deepest part of the
Karpatian source rocks started around 11.6 MY, and
they started to form gas accumulations around 9.61
MY in the anticline structures of the Karpatian
sandstones. Hydrocarbon gas accumulations were
trapped in the Badenian carbonate formations too
but no accumulations can be observed in the
Pannonian sediments despite the possible upward
migration along the neo-tectonic fault elements.
It was concluded that one part of the southern sub-basin has either higher thermal
up-heating or more deeply buried in the past than its recent structural position. The
maturation of the source rock could reach the top of oil window in much shallower
depths near this anomaly. Better understanding of the spatial heterogeneity of this
complex geological and hydrocarbon system and the results of the basin modelling
process bring new exploration perspectives for explorationists in this matured area.
The subsidence history of the investigated sub-
basins was significantly different. The main
difference is the thickness of the Karpatian
formations. While in the northern sub-basin barely
100 m thickness can be supposed; in the southern
sub-basin it can reach 3500 m thickness based on
our interpretation. The Miocene sediments of the
southern sub-basin affected by a certain degree of
inversion, which could already start during Badenian
and continued in the Early Pannonian. Thickness of
the Pannonian sediments is significantly different in
the sub-basins too. In the southern basin the
Pannonian sediments above the Pre-Pannonian
formations are much thinner than in the northern
basin. All of these facts made the model very
complex along the 2D section.
3. Model building, parameterization
In the studied area the source rocks are organic matter rich parts of the Karpatian and Badenian
sediments. Based on the Hydrogen and Oxygen Index values the Badenian source rock contains type II,
the Karpatian source rocks contain mainly type III kerogens (Fig.3.). During modelling the
Pepper and Corvi (1995) TII (B) kinetic model has been applied in case of Badenian source rock in the
southern basin, while in the northern basin TII-S(A) model has been used because of the expectedly high
sulfur content of the source rock (based on oil samples, and evaporite presence). In case of Karpatian
source rocks the TIIIH (DE) kinetic model has been applied.
During maturation of source rocks the heat flow is one of the most important factors. The applied
heat flow profiles (Fig.5.) are the results of the calibration to the measured temperature and vitrinite
reflectance values in the 4 investigated wells.
Fig.3. Van Krevelen diagram of
Hydrogen and Oxygen Index
values measured in the Badenian
and Karpatian source rocks
During modelling some of the input parameters were estimated, such as the eroded sediment thickness
due to erosion events, the paleo water depth, the heat flow history, the role of faults during hydrocarbon
migration and the original organic geochemical parameters of source rocks.
Fig.5. Estimated heat flow history in the wells
Fig.6. Estimated paleo water depth in the wells
Fig.4. Detected eroded sediment thickness on the borehole logs of Well-2 compared to
Well-1. In Well-2 on the running of log curves a sudden change can be observed between
marl and silty claymarl, in Well-1 this transition is continuous
Three erosion events were considered during model building.
The first one happened on the boundary of Badenian and
Sarmatian stages about 13 MY ago with average 50 m estimated
eroded thickness.The next erosion event occurred at the end of
Sarmatian time in the inverted southern sub-basin, 50-100 m
eroded thickness was estimated. The third erosion event could
be detected at the boundary of the Pannonian prodelta marl and
silty claymarl approximately 50 m erosion is estimated based on
borehole logs of Well-2 (Fig.4.).
The investigated sub-basins had different evolution
histories, so different paleo water depths have been
determined along the section (Fig.6.). In the Pre-
Pannonian ages it was estimated based on literature
and paleontological investigations of wells. In Pannonian
it was estimated based on calculations of decompacted
sediment thicknesses. Fig.7. shows the supposed
connection between paleo water depth and sediment
accumulation.
Fig.7. Supposed connection between paleo
water depth and sediment accumulation
Based on vitrinite reflectance values measured in the 4 investigated wells we
could determine: the sediments in Well-2 reach the oil window in significantly
shallower depths than sediments in the other wells. Compared to the Well-1
this depth difference is around 800 m (Fig.8. and Fig.9.).
Fig.8. Vitrinite reflectance values
measured in Well-1 and Well-2
Fig.9. Vitrinite reflectance values measured in the investigated wells
2. Seismic interpretation
During seismic interpretation the Karpatian, Badenian, Sarmatian and Pannonian formations were interpreted based on
drilling results of the 5 wells along the section, analogies and literature (Balázs and Nusszer, 1987; Tóth-Makk, 2007;
Magyar et al., 2013). Assignment of the Karpatian source rocks was based on the TOC (Total Organic Carbon) and POT
(Potential; S1+S2) contents measured in Well-4; if these values reached the good classification (TOC ≥ 1 wt%,
POT ≥ 6 mg HC/g rock), we considered it as source rock. The southern sub-basin has been interpreted as a half-graben
with a normal fault on its eastern edge, started to sink in the early Karpatian age. During the Badenian - early Pannonian
ages this sub-basin had strong inversion phases. One of the result of this uplifting is the observed lateral facies change of
Szolnok Formation from north to south. The northern sub-basin started to form later in the Badenian, and does not show
significant inversion phenomena (Fig. 2.)
Fig.2. Interpreted seismic section on the study area
This study is focusing on a hydrocarbon exploration area in the southern part of Danube-Tisza
Interfluve, Hungary. The studied sub-basins (northern and southern) formed during
the syn-rift phase of the Pannonian basin development, along strike-slip zones – however
under different time and geological setting. During our work a two dimensional (2D) basin
model of subsidence and maturation history has been prepared for the Neogene sedimentary
succession. With the help of the numerical basin modelling we were able to simulate and
image the geological processes during the development of the two sedimentary sub-basins.
Our goals with the current modelling were to determine the hydrocarbon potential, the time of
hydrocarbon generation, the migration pathways of generated hydrocarbon and the potential
accumulations. The data for the modelling was derived from 3D seismic volume, drilling results
and literatures. The 2D basin model has been prepared along a selected 2D section from the
3D seismic data set (Fig.1.).
1. Introduction
Fig.1. Location of the interpreted and modelled
section (geological map after Haas et al., 2010)