The Exploration II oil drilling platform in Wushi oilfield. [Photo provided by CNOOC]

BEIJING - China National Offshore Oil Corporation (CNOOC), one of the country's three fuel producers, reported waning profitability on Wednesday, mainly due to prolonged weakness in oil prices.

The company's net profits decreased 56.1 percent in the first half of 2015 to 14.7 billion yuan ($2.3 billion), according to its interim financial report.

While international oil prices hover at low levels, the company's oil and gas sales declined by 34.2 percent to 77 billion yuan.

CNOOC's net production of oil and gas grew 13.5 percent in the first six months to 240 million barrels of oil equivalent.

Chairman Yang Hua said CNOOC's efforts to reduce costs and enhance efficiency in development and production operations achieved "outstanding results", and oil and gas production significantly increased year on year.