The northwest Ionian Sea is subdivided into three distinct geological areas; to the east, the external parts of the Hellenides thrust-and-fold belt (Hellenides TFB) the central area of the south Adriatic basin, and to the west the Apulian carbonate platform. The Ionian Block lies over the central and western areas of the northwest Ionian Sea. Only its eastern border is covered by thrusts.
The south Adriatic basin is a transition between the Apulian platform and the deep-water basin in front of the Hellenides TFB. The main reservoirs in this area include shallow-water bioclastic carbonate build-ups along the platform edge, redeposited carbonates (calciturbidites) along the base of the platform slope and Oligocene-Miocene sandy layers belonging to the flysch series deposited at the front of the main Hellenides thrusts. The Messinian evaporites, where present, along with the mudstone beds (marls, clays and shales) of the flysch deposits and the Pliocene shales seal the reservoirs in this area.
The western parts belong to the Apulian shallow-water carbonate platform. The reservoirs in this area are karstified carbonate rocks, sealed by the argillaceous Pliocene deposits.
The hydrocarbon charge in this area is characterized by the proven hydrocarbon generation from Late Triassic source rocks (sabkha or lagoonal environments), Early Liassic intra-platform basin deposits and lacustrine organic-rich facies offshore Apulian platform deposited during the Turonian unconformity event. The oil and gas discoveries offshore Albania and Italy are valid indicators of a working petroleum system in the northwest Ionian Sea.