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Geology and Hydrocarbon Habitat of the Amu-Darya Region (Central Asia)

STOECKLIN, JOVAN, and T. ORASSIANOU, Petroconsultants S.A., Geneva, Switzerland

The Amu-Darya region, shared by the Soviet Republics of Turkmenistan, Uzbekistan, and Tadzhikistan, is the second-largest gas province of the USSR after western Siberia both production and reserves. Its more than 180 gas, gas-condensate, and minor oil fields include 6 giants with reserves of over 3 tcf, such as the Sovietabad field of eastern Turkmenistan, which in 1989 produced nearly 1 tcf of gas and which had an initial recoverable reserve of 38 tcf of gas. Oil in addition to gas is produced mainly in the eastern Uzbekian and Tadzhikian parts.

The region represents a large depression covering the southeastern portion of the epi-Hercynian Turan platform to the north of the Alpine-Himalayan fold belts of northeastern Iran and northern Afghanistan. Continental, paralic, lagoonal, and shallow-marine environments characterized Mesozoic-Tertiary platform sedimentation, with maximum sediment thicknesses of about 10 km in the Alpine foredeeps at the southern platform margin. Large amounts of essentially gas-prone organic matter accumulated in the Late Triassic to Middle Jurassic. Main hydrocarbon reservoirs are Callovian-Oxfordian shelf-platform and reefal carbonates under cover of thick Kimmeridgian-Tithonian salt, and shale-sealed Lower Cretaceous continental and near-shore deltaic sandstones. In the Tadzhik basin in the extreme ast, oil is contained in Lower Tertiary fractured carbonates interbedded with bituminous shales. Synsedimentary differential movements and gentle folding in the Miocene to Pliocene were the main trap mechanisms.

The region has still a considerable undrilled future potential, particularly in its deeper southern parts.

 

AAPG Search and Discovery Article #91007© 1991 AAPG International Conference, London, England, September 29-October 2, 1991 (2009)