Petroleum Systems of Turkish Basins
Turkey is a structurally complex area where two major oceans closed with superimposed structural deformation. Part of it is situated geologically on the northernmost edge of the Arabian plate as a passive margin (Southeast Anatolia) on one side, and the southern part of the Eurasian plate as a passive margin (part of Black Sea region) on the other during the Paleozoic and the early Mesozoic time. These two major plates collided during late Cretaceous to Eocene time, and the Anatolian Plateau is sandwiched between these continents. The collision has created two important suture zones, and different basins were formed in front of and in between the suture zones. Stratigraphy of these areas markedly differ from each other. In southeastern Turkey, where most of the petroleum production is located, both Paleozoic and Mesozoic petroleum systems are present. Paleozoic, especially Silurian sections, contain organic-rich source rock, and some of the oil is linked genetically to these source rocks. Middle Cretaceous source rocks are probably responsible for charging the majority of the reservoirs in the region. Mostly structural traps are drilled and stratigraphic traps are not fully evaluated. Cretaceous reservoirs are main producers, but Paleozoic reservoirs are also present. Petroleum systems in the interior basins are not fully resolved yet, due to insufficient and incomplete studies. Locally, Cretaceous and Eocene organic rich source rocks are present. Younger (Oligocene and Neogene bituminous shales) source rocks are present and generate oil. Northern areas (Black Sea) contain both Paleozoic and Mesozoic organic-rich source rocks. Live oil shows are present and known historically in different parts of the region. Some gas production is present from offshore fields. The Thrace Basin, where oil and gas have been produced for a long time, has Oligocene petroleum system. Eocene reservoirs are mostly productive.