Persian Gulf Oil and Gas Basin

or Mesopotamian Basin, a basin extending more than 2,500 km northwest to southeast (from the foothills of the Eastern Taurus in the north to the Arabian Sea in the southeast). The Persian Gulf Oil and Gas Basin is located in Saudi Arabia, Iraq, Iran, Oman, the United Arab Emirates, eastern Syria, southern Turkey, Kuwait, Bahrain, and Qatar. A small southeastern part of the basin is occupied by the Persian Gulf.

The basin contains one of the world’s largest petroleum reserves, which are estimated at 50 billion tons (1973) and account for approximately 70 percent of the petroleum reserves of all foreign countries (excluding socialist countries). The first petroleum deposit was discovered in the basin in 1908 at Masjed Soleyman, Iran. Oil-well extraction began in Iran in 1913 and in Iraq in 1927. Persian Gulf petroleum production exceeded 10 million tons in 1935 and 250 million tons in 1960.

The basin lies within a large piedmont depression, which is bordered in the north and northeast by mountains of alpine age —the Taurus in Turkey, the Zagros in Iran, and the al-Hajar in Oman—and in the southwest by the slope of the Nubian-Arabian shield of the pre-Cambrian African-Arabian platform. In the south the basin is bounded by a shelf or the shallow bedded (of the plate) foundation of the Hadhramaut plateau.

The Persian Gulf Oil and Gas Basin is composed of Paleozoic, Mesozoic, and Cenozoic rocks, whose thickness increases from southwest to northeast. In the pre-Zagros portion the rocks extend to depths exceeding 15 km. The basin is represented in section by terrigenous Neogene rocks (to 10 km), including a thick (to 3,000 m) salt-bearing series of the Middle Miocene (the Lower Fars suite). The underlying deposits, down to the Carboniferous system inclusively, are represented by mainly carbonaceous rocks. The Devonian and older deposits include mostly terrigenous rocks, and the Cambrian deposits mostly salt-bearing series.

The basin’s structure exhibits a clearly demarcated piedmont folded edge, the deposits of which are dislocated into a system of linear-elongated folds complicated by thrusts, which include salt-bearing rocks and a platform edge with large uplifts (rises) and depressions, numerous local domes, and brachyanticlines disrupted by fractures.

The petroleum deposits are contained in highly porous and permeable limestones and, less commonly, in primarily Cretaceous sandstones and Jurassic limestones. The gas deposits are contained mainly in Cenozoic limestones; they are also in Trias-sic and Permian deposits, but these reserves have not yet been explored. The oil and gas deposits are represented by domes, brachyanticlines, and rolling uplifts. A large part of the oil and gas deposits and much of their reserves are found at depths between 1,800 and 3,000 m. The oil has a 1-2 percent sulfur content and a density of 0.815-0.880 g/cm³; in the northern part of the basin (Turkey, northern Iraq) the oil has a higher sulfur content and is denser.

More than 140 petroleum deposits and more than ten petroleum and gas deposits have been discovered in the basin. Among the petroleum deposits, more than 50 have recoverable oil reserves of more than 100 million tons each, including 15 deposits each having reserves of more than 1 billion tons each (Ghawar, Kirkuk, Burgan, Marun). A large number of the deposits are in Saudi Arabia and Iran. An enormous gas-condensate deposit (reserves of 1.4 trillion cu m) exists in the Pazanan petroleum and gas deposit in Iran.

In 1973 the annual petroleum production in the basin surpassed more than 1 billion tons, including approximately 500 million tons in Saudi Arabia and Iraq. Further development of the basin will center on the search for petroleum and gas in the Persian Gulf and in the southern part of the basin, near the Rub al Khali desert basin.