Nigerian crude looked set for a sizeable overhang on Tuesday with more than half the April programme still available, with the May schedules due out within the next week.
Demand has been weak as refinery maintenance in both Europe and Asia is set to peak in May. April loading Angolan has sold better than Nigerian with less than 10 cargoes left.
The differentials for Russian Urals have slumped in the last few weeks prompting European refiners to favour the medium, sour grade instead of expensive west African crude, a trader said.
Another trader said differentials for Nigerian crude would have to correct sharply lower to elicit interest.
The Urals price in Northwest Europe hit its lowest level since September 2016 last week while the price in the Mediterranean fell to its lowest since 2014.
Competing light grades in the Mediterranean such as Saharan Blend and CPC Blend have also been under pressure, falling to their lowest levels since October.