The geology of western and southern Greece has been influenced by the movements of the Eurasian and African plates since late Cretaceous times, when they began to converge and collide. Western Greece is part of the Alpine Mediterranean Orogenic Belt comprising the Alpes, Dinarides, Albanides and Hellenides. The External Hellenides consist of NNW to SSE trending geotectonic zones that are part of the fold and thrust belt system of Western Greece. After large deposition of Triassic evaporites and platform carbonates, basin development began in the Early Jurassic due to crustal extension affecting the southern Tethyan margin. To the west, play types are controlled by thrust belt tectonics and related foreland basins, while to the south and south-western offshore play types are controlled by the Hellenic accretionary prism, including the forearc and Mediterranean ridge of the Hellenic subduction zone.
The Ionian geotectonic zone is the outermost deformed part of the External Hellenides fold and thrust belt. It comprises three stratigraphic sequences documenting the evolution of the Ionian from a neritic carbonate platform environment to a pelagic basin that are attributed to pre-, syn-, and post-rift stages. The lowermost sequence consists of a thick Triassic evaporite series, in parts brecciated, overlain by Upper Triassic to Lower Jurassic shallow-water limestones. The syn-rift sequence reflects a general deepening of the area, i.e. the formation of the Ionian Basin, with shales (Posidonia) and limestones being deposited into differentiated basins with half-graben geometries and subject to differential subsidence.
The post-rift sequence consists of Lower Cretaceous to Eocene basinal limestones and paleo-margin ward thickening brecciated limestones overlain by a clastic succession of uppermost Eocene to Lower Miocene (Flysch deposits), a Mid-Miocene molassic series and younger sediment cover. The Katakolon oil discovery located in Upper Cretaceous to Paleocene/Eocene carbonate reservoirs of the Ionian Zone is sealed by Plio-Quaternary shales The Albanian Marinez discovery may serve as an analogue here, extending the area of interest from Western Peloponnesus in the south up to the northern tip of Western Greece. North-west Greece offers folded and well-sealed anticlines. Similarities are seen in the Albanian Delvina gas condensate discovery in Cretaceous-Paleogene carbonate reservoirs, which are trapped in Oligocene Flysch sealed fold-belt anticlinal structures.The Apulian geotectonic zone, including the Apulian Platform and the Paxi (or Pre-Apulian) zone, is the westernmost undeformed part of the External Hellenides and is being overthrust by the Ionian geotectonic zone to the east. The Paxi zone on the eastern margin of the Apulian carbonate platform is composed of three primary packages. The first is alternating strata of Upper Triassic to Middle Jurassic dolomite, limestone and anhydrite deposits overlain by Upper Jurassic to Lower Cretaceous slightly cherty and marly limestones deposited contemporaneously with the Ionian Basin development (Figure Ionian Aquila Analogue). The second is Cretaceous through Paleogene to Lowermost Miocene locally brecciated shallow-water carbonates with slope and basinal marlstones, sands and shales. The third package consists of Langhian to Recent molassic sediments which are alternating marl, sand and shale. Main tectonics occurred at the Miocene/Pliocene base. The Apulian Platform and its marginal areas offshore Northwest Greece offers several targets. Further to the north of the platform the Italian Rospo Mare heavy oil discovery is found in karstified limestones of the actual platform and the Italian Aquila oil discovery is structurally trapped in redeposited carbonates off the Apulian platform margin.
The south of Crete is a frontier area with complete lateral succession of an ocean-arc boundary from the Mediterranean Ridge to the Hellenic trench system and the Hellenic fold and thrust belt. Mesozoic to Pliocene and Recent sediments, including Messinian evaporites, were found directly south of Crete. Published descriptions of mud volcanoes as well as gas emissions and their geochemistry indicate active thermogenic systems with potential for hydrocarbon accumulation.