The Impact of Neogene Thermal Blanket to the Maturation of Mesozoic Source Rocks, W. Greece

Summary This study, based on the analysis of vintage offshore seismic-reflection profiles and a newly acquired 3D PSDM seismic volume from the western Patraikos Gulf (WPG), provides a new perspective on how Miocene basin formation might have a significant impact on thermal maturation and hydrocarbon generation in fold-and-thrust geological settings. The WPG Miocene basin is developed on the western part of the Patraikos exploration block showing a strong southward thickening trend to the south. The base and top of the Miocene basin in WPG are expressed by two regional erosional unconformities, whereas a salt diapiric wall/nappe has been attributed to Triassic salt exhumation. Seismic stratigraphy indicates a basin infill, ranging from fluvial – lacustine and progradational deltaic deposits at the base to placid marine deposits towards the top. The presence of pockmarks combined with the potential source rock intervals within the Mesozoic carbonate sequence raise the hypothesis of late thermal maturation due to Miocene subsidence. Preliminary 1D basin modeling suggests that: a) the thickness of Miocene missing section is critical to source rock maturation; b) the main oil expulsion window for Triassic source rock is within the middle-late Miocene; c) The Posidonia oil expulsion window is critical to late charging.