Abu Dhabi National Oil Co (Adnoc) is operating its newly expanded Ruwais refinery at just above 70 per cent of capacity after it recently had to shut a secondary unit, industry sources said.
The refinery was running at near maximum capacity in July with its residue fluid catalytic cracker (RFCC) - a unit which processes heavy fuel oil into higher valued products such as diesel and gasoline - operating at about a 90 to 95 per cent use rate, one of the sources said.
But an unexpected outage at the RFCC earlier this month forced a reduction in the refinery's run rate.
The extent of the problem is not clear, but the unit typically takes four to six weeks to fix, the source added.
"The crude distillation unit, hydrotreater and hydrocracker units are all working fine," the source said.
"The RFCC is a very complex unit so it's not clear how long it will take to fix it."
Adnoc has been slowly ramping up the crude distillation unit's (CDU) operating rate since the RFCC outage and is aiming to have it at about 75 per cent by end-August, the source said.
Term exports of middle distillates from the refinery will not be disrupted as half the volumes contracted are optional cargoes. The refiner's inventory levels are also enough to meet term obligations, industry sources said.
Adnoc offered a large volume of straight-run fuel oil and Murban crude for this month and next, because of issues with the RFCC unit.
The more than 800,000 barrels-per-day newly expanded refinery, faced start-up issues with the RFCC when it started operations in May.