Onsan S-Oil's new residue upgrading complex (RUC) and olefin downstream complex (ODC) has been inaugurated at the company's Onsan Refinery in Ulsan, South Korea . The project, which cost around USD 4-billion, involved construction of a plant to upgrade low-value residue oil to high-value gasoline and propylene.  The propylene is to be used for the production of 405 kta of polypropylene (PP) and 300 kta of propylene oxide. Separately, S-Oil and Saudi Aramco, a majority shareholder in S-Oil, signed a memorandum of understanding (MoU) to collaborate on a USD 6-billion steam cracker and olefin downstream project. Completion is expected by 2024. PCN earlier reported that the project would include a 1.5 mta steam cracker, which would produce ethylene and other basic petrochemicals from naphtha and refinery off-gas. The downstream units would include the production of polyethylene and PP.