PS to above:

Outlaw, I still think you're wildly overrating the importance of categorizing Russian oil as "sour". Urals is in fact a medium sour blend with API gravity of around 31.2 and sulfur content of 1.35%. That's comparable to Arab Light and other major blends and is pretty much within the operating range of most major refineries. As a distinction it doesn't really matter much. It won't price as high as the very light sweet product, but it's not dedicated to specific markets either.

This is quite different from, say, the extremely heavy and extremely sour product that dominates Venezuelan exports, which really does require specialized refining and transport. Fortunately for the US, Canada produces a very similar product from its tar sands, so US refineries designed specifically for Venezuelan oil have been able to use Canadian product. That of course is a problem for Venezuela, as their crude cannot just slot in anywhere.

Again, it's likely that oil prices will be below $100 for the medium term future, and this will put some hurt on the Russians. Whether or not that's going to affect their decision making process in the Ukraine is another question altogether.