Sequence Stratigraphic and Petroleum Geologic Model of the Brakish and Nonmarine (Late Middle Miocene - Pliocene) Strata of the Pannonian Basin, Hungary

Gabor A. Vakarcs, Peter R. Vail, Ferenc Horvath

The Pannonian Basin became isolated from the world sea at 11.5 Ma and formed a large lake. It offers a good opportunity to show the distribution of depositional sequences, source rocks and reservoirs within a lacustrine basin.

The Middle Miocene-Pliocene infill of the back-arc Pannonian Basin of Hungary involved the advance of deltas from the basin margins. Twelve composite depositional sequences were identified, based on interpretation of 7000 km 2D multifold seismic sections and 130 hydrocarbon exploration and production wells. The number and the age of these depositional sequences, dated by magnetostratigraphic data, correspond well to that of the published global eustatic curve. All of the depositional sequences are complete sequences, containing braid or self margin, transgressive and highstand systems tracts. These sequences are mostly Type-1 depositional sequences and are built up from order sequence and/or parasequence sets. The identified depositional sequences were correlated to create paleogeogra hic maps.

The lacustrine depositional sequences show the same stratal patterns as the marine ones. However, deposited within slightly separated subbasins, these lacustrine sequences are more sensitive to changes in tectonic subsidence, eustasy, sediment supply and climate, in a lateral direction. There are several identified fourth-order sequences in which Type-1 and Type-2 behavior can be seen in the same sequence. These are "apparent Type-2 sequences", developed in response to variations in sediment supply.

Using sequence stratigraphy to recognize sequence boundaries, stratigraphic traps and source rocks and effects of late-stage compression, has resulted in enhanced input data to simulate the subsidence, thermal, and maturation histories of the Pannonian Basin.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995