By Ben Aris in Berlin Ukraine continues to attack Russian refineries with drones but as drones only carry to 5-50kg explosive payload, rather than the 500kg carried by bombers, they can’t destroy a refinery, only damage it. The attacks have a high PR value for Kyiv, but so far they have had little practical impact on Russia’s export revenue or the international prices for crude or refined oil products. The attacks have reduced Russia’s oil refining volumes by an estimated 14%, but as Russia has a refining capacity that is 2.5 times larger than its own needs, this reduction has had little impac…