Gazprom 1980s, the Ministry of Gas Industry found large natural gas reserves in Siberia, the Ural region and the Volga region. The Soviet Union became a major gas producer. In August 1989, under the leadership of Viktor Chernomyrdin, the Ministry of Gas Industry was renamed the "State Gas Concern Gazprom", and became the Soviet Union's first state run corporate enterprise. In late 1991, when the Soviet Union dissolved, gas industry assets were transferred to newly established national companies, such as Ukrgazprom and Turkmengazprom. Gazprom kept assets located in Russia and secured a monopoly in the gas sector. In December 1992, when
Gazprom in the Nadym-Pur-Taz region (near the Gulf of Ob) in Yamalo-Nenets Autonomous Okrug in Western Siberia. Historically, the three largest fields are Medvezhe, Urengoy and Yamburg. After more than twenty years of production, the fields are now in decline. Production from the fields has decreased by twenty to twenty-five bcm per year. The production at Zaporliarnoe, Gazprom's fourth largest field, increased until 2004, offsetting the decline in the other fields. Since 2004, Gazprom has maintained production by activating new smaller fields and by purchasing production assets from other companies. Gazprom Neft produces crude oil. In 2005, Gazprom purchased 75 percent