China's largest crude production base, located in Bohai Bay, has produced more than 500 million metric tons of oil and gas equivalent so far with annual production gradually rising each year, said its operator China National Offshore Oil Corp, the country's top offshore oil and gas producer.

Oil and gas production in Bohai oilfield exceeded 30 million tons last year, which is half of the country's crude oil output increase in 2021, it said.

"Five hundred million tons of oil is approximately equivalent to the basic demand of the country for one year and it has also significantly contributed to the country's domestic energy security and economic development," said Wang Yu, production manager of the company's Tianjin branch office.

Li Ziyue, an analyst with BloombergNEF, said CNOOC's steady oil and gas production ramp-up is critical to China's energy security.

"This is even more important amid current geopolitical tensions, which have launched commodity prices to new highs," Li said.

"Oil and gas supplies, especially, are under extra pressure, while China's offshore oil and gas output has great upside potential."

The State-owned producer contributed more than half of China's total oil and gas output addition last year and it is also trying to carve out a role in the country's growing clean energy sector, seeking to use its engineering prowess to become a major player in offshore wind power projects, she added.

According to the China Offshore Energy Report drafted by the CNOOC Energy Economics Institute earlier this year, China is one of the most active areas for offshore exploration and ranks fourth in newly launched offshore oil and gas production projects.

The institute expects China's offshore oil and gas output will continue to rise this year.

Bohai oilfield started construction in 1965 and is the birthplace of China's modern offshore oil industry.

After over half a century of service, it has come up with more than 50 productive oil and gas fields, over 180 production facilities with accumulative proved petroleum geological reserves of more than 4.4 billion tons and natural gas geological reserves of some 500 billion cubic meters.

It has become the country's most profitable and largest-in-scale offshore oil and gas field, said CNOOC.