Chinaoil swept up most of the 223 partials from Chinese state trader Unipec during the Platts Market on Close (MoC) price assessment process, they said.
This sent the premium above swaps on Dubai, the Middle East crude benchmark, close to $1.60 per barrel, its highest in at least a year, Reuters data showed.
The trades will result in Unipec delivering 10 Middle East crude cargoes or 5 million barrels to Chinaoil, the largest volume ever to be delivered in a single day via the MoC, traders said.
These include five Oman, one Dubai and four Upper Zakum crude cargoes, they said.
Separately, Reliance Global Energy Services, the trading arm of Indian refiner Reliance Industries, sold its first partial to Chinaoil during the MoC process, traders said.