Middle East crude markets remained weak on Wednesday, with Qatar Marine crude for June lifting extending its losses, weighed down by a recent plunge in Oman crude values. At least one cargo of June Qatar Marine changed hands at a discount of around $1.20-$1.30 a barrel to official selling prices (OSP), down from a discount of around $1.00 seen earlier in the month, traders said. Oman’s front-month June contract had fallen into a discount to Dubai quotes on Tuesday, but flipped back to a premium of 21 cents a barrel by 0830 GMT, Reuters data showed. Surgutneftgaz, Russia’s fourth-largest oil producer, sold five cargoes of ESPO crude for June-July loading at lower premiums than the previous month after values for rival Middle Eastern grades slumped on ample supply, traders said on Wednesday. The cargoes were sold at premiums between $3.30 and $3.90 a barrel to Dubai quotes, they said. Only one cargo was sold at a premium below $3.50 a barrel, a trader said. Sudanese oil workers took stock of damage to the economically vital Heglig oilfield on Tuesday after recent fighting with South Sudan left a power station in ruins, a warehouse gutted and a pipeline spilling out acrid crude.