Sanctions on Venezuela's oil firm sends U.S. refiners scrambling

The United States on Monday imposed sanctions on Petróleos de Venezuela, S.A., known as PDVSA, to cripple the OPEC member's oil shipments, which account for nearly all of Venezuela's exports, in response to the reelection of socialist President Nicolas Maduro, a vote widely viewed as fraudulent.Washington has recognized opposition leader Juan Guaido as Venezuela's head of state.U.S. refineries that depend on Venezuela's heavy crude are turning to domestic sour crude grades to offset the i