YUKOSProven oil reserves: 14.71 billion barrelsProven gas reserves: 9.94 trillion cu ftTotal oil production (2003): 591 million barrelsTotal gas production (2003): 199.7 billion cu ftYUGANSKNEFTEGAS/ROSNEFTProven reserves (oil equivalent): 11.63 billion barrelsFirst began operations in 1964; has produced over 10 billion barrels till date. Manages 26 fields including Priobskoye and PrirazlomnoyePRIOBSKOYERecoverable reserves: 3.01 billion barrelsAverage daily production (2003): 0.35 million barrelsInvestments (2003): $452 million