The Urengoy natural gas and condensate field
The Urengoy natural gas and condensate field in the Western Siberian Basin is Russia's largest gas field and also one of the largest onshore deposits in the world. The reserves that can be extracted have been estimated at around seven trillion cubic metres of natural gas. The deposit was discovered in the 1960s and the systematic development and production was started in 1977. The extreme environmental conditions (permafrost, cold, tundra and the sensitive ecosystem) made development of the deposit extremely difficult. Today the OAO Gazprom subsidiary Gazprom dobycha Urengoy produces 260,000 million m3 of gas, more than 5,000 tons of condensate and 825,000 tons of oil each year.
The Urengoy Field stretches in a north-south direction for more than 230 km and is between 30 and 60 km wide. The largest part of the deposit is north of the Polar Circle. The sandstone which currently produces the gas is mainly from the Upper Cretaceous period - approx. 90 million years old - and is located at a depth of more than 1,200 metres. The wells are drilled in so-called well clusters - generally consisting of two to seven wells. In this way the impact on the sensitive ecosystem is kept to a minimum.
More gas producing horizons exist at deeper layers of more than 3,500 metres. These are sandstone layers from the Lower Cretaceous Achimov Formation. These consist of moderately porous, but low permeable sandstone. From a geological aspect, this horizon, in which both gas and oil are to be found, evolved around 140 million years ago. This geological formation is very common in western Siberia and can be found in many fields.
