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AAPG Europe Regional Conference, Global Analogues of the Atlantic Margin

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An analogue study of petroleum systems: West Iberian Basins vs East European Basins

Abstract

The purpose of this paper is to describe the stratigraphy, sedimentology and evolution of the petroleum systems in the West Iberian Basins and to highlight the correlation with the petroleum systems in the East European Basins, especially those formations affected by the salt tectonics. The data used in this paper comes from original research and field observation as well as published papers and technical reports. Petroleum systems elements include Palaeozoic and Mesozoic source rocks, siliciclastic and carbonate reservoir rocks, and Mesozoic and Tertiary seals. There are both similarities and differences between the Western Iberian Basins and the East European Basins, the differences being mainly related to the later onset of the main rift phase in the East European basins which was accompanied by Neogene subsidence and burial. Traps are in general controlled by diapiric movement of the evaporites during the Late Jurassic (Western Iberian Basins), Late Cretaceous and Late Miocene (both Basin Systems). Organic matter maturation, mainly due to rift-related subsidence and burial, is described together with hydrocarbon migration and trapping. In the East of the Alpine-Carpathian-Dinaric orogenic system, hydrocarbon traps are formed by domes and domelike anticlines as well as by stratigraphic traps. The domes were created by salt diapirism, which was probably induced by the rapid burial of the evaporitic layer at the base of the middle Miocene sedimentary sequence. The stratigraphic traps are a result of facies changes related to molasses sedimentation that is characterized by a thick sequence of ungraded, crosbedded sandstone, shale and marlstone. On the other hand in the Western Iberian Basins we can identify three main petroleum systems, sourced respectively by Palaeozoic shales, Early Jurassic marly shales and Late Jurassic marls. The unconformities recorded in the Iberian sedimentary basins can be correlated with episodes of compression between Iberia, Eurasia and Africa. The sedimentary record of the major basins includes continental units in the interior which, progressively, pass to marine sedimentation in areas closer to the present coastlines of the Atlantic and the Black Sea respectively, reflecting various paleogeographic, tectonic, climatic and eustatic events. In conclusion, this paper has shown the many similarities as well as the differences between the basins located in the Western and Eastern extremities of the Alpine-Carpathian-Dinaric orogenic system using data from both geophysical prospecting (2D and 3D seismic interpretation) and well logging as well as published papers on stratigraphy, sedimentology and petroleum systems in the studied areas. The data is integrated and interpreted in order to build up an updated petroleum systems analysis of the basins.