After several lean years, output at CNOOC Ltd (0883) is expected to rise this year following the discovery and appraisal of several large oil fields in Bohai Bay.

China's largest offshore oil firm saw shares jump as much as 5 percent on the news, before closing at HK$16.08, up 3.3 percent and outperforming two other mainland oil giants listed locally.

CNOOC said its Penglai 9-1 oil block, discovered in 2010, has been appraised as a large oil field. One of the wells, 9-1-5, was tested to produce 700 barrels per day.

The company said it is the largest Bohai oil field discovered in recent years. The 9-1-5 well is about the same size as another that saw production stalled since September due to a leakage.

Also discovered was the 15-2 oil block, some 8 kilometers south of the 9-1 field. A well there is expected to produce 1,200 bpd.

Analysts at Daiwa estimate the 9-1 field can produce 200 million barrels of oil, and believe the discovery can lift CNOOC's value by HK$0.4 per share.

Last year, the company produced 331.8 million barrels- equivalent of oil and gas, flat from 2010. In January, it put its 2012 output target at 330 to 340 million boe.

But it will likely surpass that target as the new fields come online.