China Oilfield Services Limited (COSL), a leading integrated oilfield services provider, posted a 31.7 percent year-on-year net profit increase as its exploration business expands.

Its net profit hit 4.13 billion yuan (629 million U.S. dollars), COSL said in its 2010 annual report filed to Shanghai Stock Exchange on Wednesday.

The company's earnings per share stood at 0.92 yuan.

COSL said its profit increase was due to expanded exploration driven by commencement of operations of key large-scale equipment.

The A-share price of the company opened up 0.52 percent from the previous close to 23.23 yuan Wednesday.