Shell bid for a July-loading cargo during the MoC process and bought it from BP at 40 cents a barrel above its OSP, they added. The crude had traded at premiums of 25-35 cents a barrel prior to Shell's purchase.
Cash Dubai and DME Oman both rose to more than 30 cents above Dubai swaps on market close.
Earlier this week, Petro-Diamond sold an Upper Zakum cargo at a premium of more than 20 cents and a Qatar Marine cargo at a single-digit premium to its OSP, traders said.
Cosmo Oil bought two al-Shaheen cargoes at 25 cents a barrel above Dubai quotes, they said.
Still, a jump in Iraqi crude exports in June and a hike in their OSPs have cooled premiums for Basra Light, traders said.
Offers of June-loading Basra Light were at 70 cents a barrel above the OSP, a trader said, down from premiums of more than $1 fetched for May supplies.
Basra Heavy's premium may stay above $1 a barrel on robust demand from Asia and the United States, another trader said.