Venezuela’s crucial oil upgraders have stopped processing heavy crude because a decline in exports due to U.S. sanctions has left the OPEC nation without sufficient storage space, seven sources familiar with the facilities told Reuters.  Three of the four upgraders, which convert extra-heavy Orinoco oil into lighter exportable grades, have started “recirculating” – a process that keeps systems running to prevent damage but does not yield new upgraded oil. The shift signals that state oil company PDVSA is struggling to maintain operations after U.S. sanctions this year eliminated its main customer by restricting sales to U.S. refiners. “The upgraders are recirculating because there is an excess of production, and there are no buyers,” one PDVSA source said. None of […]