China National Offshore Oil Corp Ltd, the country's biggest marine oil producer, said on Tuesday that its net production in the first quarter declined by 6.3 percent year-on-year to 79.8 million barrels of oil equivalent.

That decline was blamed on a halt in production at the country's biggest offshore oilfield, which is in Bohai Bay and is named Penglai 19-3.

Even so, the company said it is confident it will reach its previous goal of producing 330 to 340 million barrels of oil equivalent in 2012. The losses incurred from temporarily shutting down Penglai 19-3 are to be made up by four projects that are expected to go into operation this year, said Zhong Hua, CNOOC chief financial officer.

Zhong said the company and its partner, ConocoPhillips China, are still waiting for a government approval to resume operations at the oilfield, which leaked more than 700 barrels of crude oil in two incidents in June.

The government ordered the project to be suspended in September and has yet to provide a schedule for resuming the operation. Authorities have asked the two companies to give them an overall development plan and an environment assessment report, requests they have complied with.

CNOOC announced recently that it made five new offshore discoveries in the first quarter, both at Bohai. Zhong said the company is still assessing the projects, which are expected to begin operating within three to five years.

"Bohai will continue to be the biggest source of growth for our company in the future," Zhong said.

The company also said it received about 48.84 billion yuan ($7.7 billion) from oil and gas sales in the first quarter, an amount up 3.7 percent year-on-year.

On average, CNOOC received $120.79 for each barrel sold in the first quarter, a 19.4 percent year-on-year increase.