Saudi-based firms have been invited by Saudi Aramco Lubricating Oil Refining Co to bid for the early engineering work to expand the company's Yanbu refinery, Reuters has reported, citing industry sources. The expansion of the refinery, which has a capacity of 280,000 tpy of oil lubricants, includes a new lube hydrocracker, raising the capacity of the vacuum distillation unit, upgrading the electrical facilities and adding new storage tanks, according to one source, who declined to say what the capacity of the refinery would be after the upgrade.