It depends on the gravity of the crude. I don't know what the average number is for Russia. The advantage of using tons is that the weight before and after refining is pretty much the same, whereas the volume (barrels) increases after refining. However, when using barrels you don't have to worry about the API gravity.

In any case, are they talking about C+C or total liquids?

BTW, good article I had forgotten about, with pertinent quotes:

http://www.energybulletin.net/16745.html
Published on 3 Jun 2006 by Energy Bulletin. Archived on 3 Jun 2006.
Confessions of a statistician
by Sohbet Karbuz
(former head of Non-OECD Energy Statistics Section of the International Energy Agency)

. . . Furthermore, it is not correct to make a peak oil analysis based on “all liquids,” because the non-conventional fuels I mentioned above do not come from an oil reservoir . . .

. . . Moreover, customs office and ministry/statistics office may not agree with each other on trade statistics (e.g. Russia). . .

. . . Best data come from EIA petroleum supply monthly but it comes out 2 months after the fact. . . .

. . . Missing link - Conversion Factors: Oil statistics in the world over are expressed by using four most common conventions - litre, cubic metre, barrel, and ton. Since world oil balances are usually expressed in barrels, the selection of appropriate conversion factor is essential. Interestingly, not enough attention is paid how different measurement units for oil are aggregated and which conversion factors are in use.

Although, the relationship between volume and mass measured by density or specific gravity, the number of barrels of crude oil per ton for the same country varies widely, depending on the source. The discrepancies in conversion factors in use, although seem small, are not negligible and in fact already play an important role in world oil balance. This can be demonstrated by using the Russian crude oil production. Russia releases its oil production in tons. Take an original Russian production figure in tons for any year. Then apply EIA and IEA’s conversion factors and see the difference. Do the same exercise for other countries that measure their oil in tons. Sum them up and compare the difference. You will be surprised! . . .