Petroleum Geology and Resource Assessment of the Middle Caspian Basin, USSR, with Special Emphasis on the Uzen Field

摘要

The Middle Caspian Basin contains up to 12,000 m (40,000 ft) of sedimentary rocks ranging in age from late Paleozoic to Quaternary and has over 100 oil and gas fields varying in size from small to supergiant. The Soviet literature reviewed for this report covers: (1) tectonic zones of the basin, including details of the lower, intermediate, and upper structural complexes; (2) paleogeography, facies distribution, and conditions of organic matter accumulation in the major petroleum source rocks; (3) stages of oil and gas generation; (4) major hydrogeological features; and (5) producing regions of the basin. Total initial petroleum resources of the basin are estimated at 22.5 x 10 exp 9 t (166 x 10 exp 9 bbl), of which 16.0 x 10 exp 9 t (118 x 10 exp 9 bbl) are yet to be discovered. Resources of the offshore Caspian Sea area are estimated to be 12.1 x 10 exp 9 t (89.5 x 10 exp 8 bbl). The most promising zones for offshore exploration are the plunging continuation of the Central Mangyshlak system of uplifts and the South Dagestan area. Initial reserves (oil in place) of the supergiant Uzen field are calculated to be 1.02 x 10 exp 9 t (7.50 x 10 exp 9 bbl). Because the recovery efficiency is estimated at 26 to 39%, recoverable oil is 0.261 to 0.397 x 10 exp 9 t (1.98 to 2.96 x 10 exp 9 bbl). Analysis of the exploitation of the field shows significant difficulties related mostly to marked nonuniformity of reservoir permeability and to the high paraffin content of the oil. (ERA citation 06:031619)