"As the United States seeks to strengthen sanctions on Moscow for its occupation of Crimea, energy experts say the powerful Russian oil industry would make a robust target. But any penalties on energy investments, technology transfers and financial transactions would most likely also punish Western oil companies like Exxon Mobil that are investing heavily in Russia.
'Everything is on the table,' said David L. Goldwyn, the State Department’s coordinator for international energy affairs during President Obama’s first term. 'The calculus has to be who will be hurt most, us or them, if sanctions are put in place.'
As the heart of the Russian economy, the energy sector — led by state oil companies like Gazprom, Lukoil and Rosneft — would be a natural focus for pressure from the United States and its allies. Oil and petroleum products represent more than two-thirds of Russian export earnings, and they finance just over half of the federal budget."