Assessment of continuous oil and gas resources in Jurassic Posidonia Shales of Greece and Albania, 2019

The U.S. Geological Survey (USGS) quantitatively assessed the potential for undiscovered, technically recoverable continuous oil and gas resources in the Jurassic Posidonia Shale Total Petroleum System (TPS) of western Greece and southern Albania (fig. 1). From the Late Triassic to Early Jurassic, this area of western Greece and southern Albania was part of a regionally extensive carbonate platform that developed on and around the Apulian Plate (Karakitsios, 1995; 2013). Deposited along the passive margin during this time were as much as 1,000 meters of platform carbonates of the Pantokrator Limestone. Jurassic extension and rifting associated with the opening of the neo-Tethys Ocean led to the formation of numerous grabens and half-grabens along the margin of the Apulian Plate (Karakitsios, 1995; Karakitsios and Rigakis, 2007). The bottom waters of the deeper grabens and half-grabens were anoxic, resulting in the deposition and preservation of organic-rich petroleum source rocks of the Jurassic Posidonia Shale. These extensional structures persisted through the Jurassic and eventually were buried by the regionally extensive, postrift Cretaceous Vigla Limestone. From the Cretaceous through the Paleogene, the Apulian Plate was relatively undeformed and buried by perhaps hundreds of meters of carbonate deposits. Beginning in the Eocene and ending in the Miocene, the Apulian Plate collided with the Eurasian Plate, forming the Dinaride and Hellenide fold and thrust belts, resulting in compressional deformation of Mesozoic rocks. Associated with the collision of Apulia was the progradation of orogenic clastic wedges up to several kilometers thick (Gonzalez-Bonorino, 1996; Karakitsios, 2013). Neogene burial by these orogenic clastics resulted in the thermal maturation into the oiland gas-generation windows of the Jurassic Posidonia source rocks (Rigakis and Karakitsios, 1998; Karakitsios and Rigakis, 2007).