A shipyard under China's state-run COSCO Group has built a $600 million ultra deepwater drilling rig for Norwegian oilfield services group Sevan Marine , state media reported on Sunday.

The rig, Sevan Driller, can sink wells 40,000 feet deep and store 150,000 barrels of crude oil, Xinhua News Agency reported in its Web site, quoting a COSCO official.

The Norwegian firm, which has contracted the rig to Brazil's Petrobras, said earlier this month that it had secured options to build six more drilling units at a Chinese shipyard.