TNK-BP was a major vertically integrated Russian oil company headquartered in Moscow. It was Russia's third-largest oil producer and among the ten largest private oil companies in the world. In 2013 it was acquired by Russian oil company Rosneft. DeGolyer and MacNaughton confirmed that as of 31 December 2009 TNK-BP's total proved reserves amounted to 11.667 billion barrels of oil equivalent, applying PRMS criteria. Proved reserves constitute a total proved PRMS reserve replacement ratio of 329%.