The U.S. federal government this week declared sanctions on two of the largest Russian crude oil exporters, Rosneft and Lukoil, which together account for about half of the country’s total outflows. Oil prices jumped, traders got excited—then prices fell. But the supply security of some major importers just got problematic. Russia exports around 4 million barrels of crude oil daily. Some of the major producers have already been sanctioned earlier – Gazprom Neft, for example, and Surgutneftegaz. Rosneft and Lukoil are also the…