Geology and Prospecting of Oil and Gas Fields

In the Soviet Union the total land area prospected to be suitable for the oil and gas search amounts to 12 million sq km (sea areas not included) i.e. almost half of the whole country's territory. Successful geological survey exploration activities have resulted in finding oil reserves which are sufficient to ensure high rates of production here in the country. Over the last 20 years the level of oil output has increased seven-eightfold.

A further increase in oil and gas production is planned for the coming years. By 1975 the production of oil is expected to amount to 480–500 million tons and that of gas to 300–320 billion cu. m.

On the territory of the Soviet Union there are more than 1200 oil and gas fields and deposits and most of them have multilayered pay zones. On an average the field-deposit ratio for our country is 1 to 3.2.

Most of oil and gas deposits, about 46 per cent, have been found at a depth of 1000–2000 m and about 20 per cent of the accumulations go deeper than 2000 m.

Geological survey is well under way and its scope is gradually increasing. Nearly a thousand of specialized crews are annually engaged in seismic prospecting. 2600 m IS an average depth reached by prospecting boreholes. Quite a number of wells are drilled as deep as 4.5 and even 6 thousand meters.

Over the last ten years hundreds of oil and gas fields have been found in the areas with the advanced extracting industry and there have been found anew not only petroliferous regions but provinces abundant with oil and gas.

The main and the most outstanding result of the last ten years' geological prospecting is the discovery of a new oil – and gas-bearing province in the Western – Siberian Lowland where large-scale fields have been detected and premises have been created for the development of a powerful oil and gas extracting industry. In 1975 120 million tons of oil will be extracted in this area, and in 1980 oil recovery will amount to 230–260 million tons. The growth rates of gas recovery are planned to be exceptionally high.

The Western-Siberian Lowland IS an epipaleozoic platform with an area totalling to 2 million sq. km.

Oil and gas fields have been detected on a greater part of the plate. Within the framework of the Western-Siberian plate oil and gas deposits stand apart rather distinctively: in the Srdne-Obskaya region there prevail oil accumulations spreading over the jura-neocom section; in the Pur-Tazovskaya region there is a clearly cut zone where vast gas deposits are situated within the Senoman sandstones which are on top of the section; oil and gas condensate deposits (the Urengoy field) have been found in the lower cretaceous rocks. All in all 60 oil and 40 gas fields are known to have been detected here.

A vast area between the Caspian Sea and Tien Shan is occupied by another epipaleozoic platform – the Turanskaya plate.

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