China National Offshore Oil Corp, the parent of CNOOC Ltd, already plans to invest 45 billion yuan ($6.59 billion) to expand its new Huizhou refinery, which is expected to come on stream next month, the China News Service reported.

The expansion will boost the capacity of the refinery to 22 million tons per year from 12 million, the report said.

Construction will begin next year and the new facilities are expected to become operational in 2011.

Located in southern China's Guangdong province, the refinery is a joint venture with Royal Dutch Shell.

The report said CNOOC Refining will also build a one million ton per year ethylene facility in Huizhou.