Amudarya gas-oil-bearing province

AMUDARYA GAS-OIL-BEARING PROVINCE (RU: Амударьинская газонефтеносная провинция) is located within the central and eastern parts of the Turkmen SSR, at the west of the Uzbek SSR (the area is 360 thousand square kilometres), at the north of Afghanistan and Iran (57 thousand square kilometres). The first gas field (Setalan-Tepe, Setalantepe) has been discovered in 1953; till 1981, there have been uncovered more than 90 fields, of which more than 85% are gas and gas condensate ones, approximately 15% are gas-oil ones.

(Map) Amudarya oil-gas-bearing province

The main fields are: Shatlyk, Dauletabad, Bayramali, Kirpichlin, Achak, Nayip, Gugurtlin, Gazlin, Kandim, Lengizkul-Hauzak, Samantepin, Urtabulak (see map). Within Afghanistan, the first field (Etymtag) has been discovered in 1960; till 1982, there have been uncovered 6 oil and 6 gas fields, the main ones are Khoja-Gugerdag, Dzharkuduk (gas), Kashkarin (oil). Within Iran, the large gas field is Hangiran. Amudarya gas-oil-bearing province is situated within the Turan lowland, within the desert regions of Karakum and Kyzylkum. The major waterway is the Amudarya river. There passes at the south the Karakum canal, which is named after V.I.Lenin. There are covered by the railway network the southern and eastern regions (major line is Krasnovodsk-Tashkent); the highways are situated mainly along the railways. The transportation of gas to the Urals and Centre regions is performed through the Bukhara-Urals and Central Asia - Centre gas pipelines. Gas is supplied from Afghanistan to USSR through the Hodge Gugerdag - Kelif - Mubarek gas pipeline. The centres of the extraction are: the Gazley, Bukhara, Karshi, Chardjou, Bairam-Ali (USSR), Sheberghan (Afghanistan) cities.

Amudarya gas-oil-bearing province occupies the south-eastern part of the Turan plate and advanced Kopet Dag foredeep. The Afghan part of the Amudarya gas-oil-bearing province is mainly associated with the epi-platformal region of the neotectonic activation. The basement is Paleozoic (pre-Permian). The Permian-Triassic volcanogenic-sedimentary rocks represent the intermediate complex. The platformal Meso-Cenozoic cover reaches up to 7 kilometres.

The major gas-oil-bearing capacity of the Amudarya gas-oil-bearing province is associated with the Amudarya syneclise, within the sedimentary cover of which there has been determined the Uchadzhinsky vault, the series of the tectonic stages, depressions, downfolds, which are complicated by more than 650 local uplifts (from 2x4 kilometres to 35x25 kilometres, amplitude from tens of metres to hundreds of metres). The gas fields are confined to the Central Karakum vault, where they are controlled by the dome-like uplift, which is complicated by the small anticlinal folds.

There are productive the depositions of Jurassic and Cretaceous to the depth of 0.2-4 kilometres. The reservoirs are tabular vaulted, massive, sometimes tectonically, lithologically, and stratigraphically shielded. Within the Amudarya syneclise, within the regions of the distribution of the thick halogen stratum, the reservoirs are mainly single-layered, they have been found only within the subsalt part of the cross section of the Upper Jurassic. Within the certain fields, the reservoirs are associated with the reef-forming limestones. The productivity of the Cretaceous depositions has been determined within the regions of the out-wedging of the salt-bearing stratum, where the level of the gas-oil-bearing encompasses the entire cross section of the Jurassic and Cretaceous.

The gases are dry, mostly methan, the content of N2 is 0.1-5%, of CO2 is 0.02-4%. For the gases from the subsalt Upper Jurassic sediments, there is characteristical the elevated concentration of H2S (up to 5-6%). The content of condensate is 10-60 grams per cubic metre. The oils are low-sulfur, the content of paraffin is less than 13%, the density is 770-900 kilograms per cubic metre. For the oils of the Afghan fields, there are characteristical the increased values of density (up to 928) and of the sulfur content.