Unlike peers PetroChina Co Ltd and China Petroleum & Chemical Corp (Sinopec) , CNOOC's profit comes solely from exploration and production, making it a key beneficiary of buoyant crude oil prices.

State-run CNOOC posted a net profit of 70.26 billion yuan ($11.14 billion) for 2011, compared with 54.41 billion yuan for the previous year.

The result was in line with a consensus forecast of 69.5 billion yuan from 33 analysts polled by Thomson Reuters I/B/E/S.

Valued at about $95 billion, CNOOC shares tumbled 26 percent in 2011, underperforming PetroChina's 4.8 percent loss, and Sinopec's 9.8 percent gain in Hong Kong in the same period.

CNOOC's 2011 output was hit hard by an oil spill at its Penglai 19-3 field in eastern China's Bohai bay, which resulted in total production losses of 5.9 million boe last year.

President and Chief Executive Li Fanrong said in January that the oilfield, co-owned and operated by ConocoPhillips , should resume production this year.  ($1 = 6.3072 Chinese yuan)