Petroleum potential of the North Hungarian Oligocene sediments

As part of Eoparatethys, a partly isolated sea existed to the north of the present-day Pannonian Basin during Oligocene time. From Lattorfian times thick shale sequences, rich in organic matter, were deposited. Locally, laminates of euxinic facies formed (Tard Clay Formation) and are the best oil-prone source rocks of the Oligocene sequence. Although oil discoveries were made in the basin in the late 1930s, exploration was prevented by the complicated tectonics. Currently, detailed seismic, geological and geochemical studies have been initiated, the first results of which are summarized in this paper. Rock-Eval pyrolysis data and bituminological analysis show the Tard Clay Formation to be a good source rock. Its thermal maturity has been influenced by subsequent tectonic movements and Neogene heat flux. Migration and accumulation of the generated hydrocarbons is controlled by unconformities and, in particular, by the tectonic elements. Complicated structural and stratigraphical traps are covered by the Pliocene basal marl.