China National Offshore Oil Corporation (CNOOC), the largest offshore oil and gas producer in China, and Royal Dutch Shell, the world's leading energy and petrochemical conglomerate, signed a strategic cooperation framework agreement worth 5.6 billion U.S. dollars on Sunday. The new cooperation, based on the CNOOC and Shell Petrochemical Company Limited, is the CNOOC and Shell Huizhou phase III ethylene project.