AAPG Geoscience Technology Workshop

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Tethyan Megasequences, Isolated Carbonate Platforms and Petroleum Systems Chart: An Exploration and First-Order Correlation Tool for the Mesozoic and Cenozoic of the Mediterranean


Isolated carbonate platforms (ICPs) are spectacular features of Mediterranean geology and have long been known to host important hydrocarbon reserves, for example in the Southern Apennines of Italy. Recently there has been a resurgence of interest in the resource potential of Mediterranean isolated carbonate platforms following recent world class exploration successes in this play in the eastern Mediterranean. The scarcity of subsurface case histories in the Mediterranean Region lets open a series of questions on the characteristics of Mediterranean ICPs and their relationships with the elements of the associated petroleum systems. In order to provide a better understanding of the hydrocarbon potential of this interesting carbonate target, we have developed a regional sequence stratigraphic framework based on a proprietary database, which includes a large amount of public and original data on the carbonate systems of the Mediterranean and on the related petroleum systems. The database includes outcrop and subsurface, onshore and offshore data from 10 main regions of the Mediterranean, corresponding to present orogenic belts, forelands and passive margin settings. The proposed regional sequence stratigraphic framework defines an approach for developing systematic evaluations of the spatial and temporal distribution of ICPs and associated petroleum systems. The product developed is the Mesozoic and Cenozoic Tethyan Megasequences and Petroleum Systems Chart. It represents the first megasequence stratigraphic framework that attempts to unify Alpine Tethys and Neotethys with North Africa and Eastern Mediterranean, and it provides an exploration and first-order correlation tool for the spatial and temporal distribution of ICPs, and associated petroleum systems across the entire Mediterranean. With this approach, the Mesozoic and Cenozoic basin fill of the Mediterranean has been subdivided into 9 main megasequences. Megasequences correspond to tectono-stratigraphic units related to the Mesozoic and Cenozoic geological history of the Mediterranean Tethys, which was characterized by a complex suite of events related with the geodynamic evolution of 5 oceanic domains (Neotethys, Alpine Tethys, Mediterranean Tethys, Indian Ocean and Red Sea) and 4 main continents (Europe, Africa, Arabia and Adria). Meso-Cenozoic megasequences are separated by boundaries that represent regional seismic scale surfaces that arise from geodynamic events expressed across the entire study area or linked and approximately contemporaneous to geodynamic events expressed at the inter-plate scale. The stratigraphic record and distribution of megasequences, MICPs and the elements of the petroleum systems are integrated with some published trends, such as the stable-isotope ratios of carbon 12/13, which major excursions can be associated with widespread deposition of organic-rich sediments; the ratios of oxygen 16/18 which are important in the interpretation of past temperature; eustatic sea-level trends and major sequences as interpreted by widely used selected publications. Finally, the spatial distribution of MICPs, together with the source rocks and reservoirs is illustrated in palaeogeographic maps for each megasequence.