Buguruslanneft is one of the oldest oil producers in the area and accounts for some 4% of TNK-BP's oil output in the Orenburg Region, or 670,000-680,000 metric tons a year (about 13,600 bbl/d).
The company's press service said the move would contribute to production development, and that other assets and licenses would subsequently be acquired.
TNK-BP, which produces crude in West Siberia, the Volga-Urals region, East Siberia and Sakhalin, is currently studying the market in preparation for the sale.
TNK-BP was established in 2003 through a merger of Russian oil companies TNK, Sidanco, and Onaco and the assets of British oil major BP in Russia and Ukraine. The company produced more than 73 million metric tons (1.47 million bbl/d) in 2006.