LONDON, Nov 6 (Reuters) Russian oil major Lukoil's , opens new tab Volgograd refinery has halted operations after it was struck by Ukrainian drones, three sources familiar with the matter said on Thursday. Ukraine has for several months been striking Russian oil refineries, depots and pipelines, while Ukrainian energy infrastructure has also been the target of Russian strikes in a war that is approaching its fourth year. They said that the primary processing unit, CDU-5, with a daily capacity of 9,100 metric tons, or 66,700 barrels per day - a fifth of the plant's total capability - and a hydrocracker...