China has found its largest offshore oilfield with reserves of 600 million tons in north China's Bohai Sea.

The profitable Penglai 19-3 is believed to be the second-largest oilfield after the famous Daqing Oilfield which was discovered in 1959 in northeast China, Chinese scientists announced on January 31.

The oilfield is in the ocean floor at a depth of between 900-1,400 meters, covering an area of 50 square kilometers, revealed Deng Yunhua, geologist in charge of the Bohai Oilfield near the port city of Tianjin.

The joint exploration was done by the China National Offshore Oil Corporation and the Phillips Oil Corporation of the United States over the past six months; it is the biggest discovery for the US company in the past 3 decades.

Since China opened part of the Bohai oil exploration territory to overseas firms in 1980, few major discoveries have been reported due to a miscalculated theory that oil reserves were available 3,000 meters deep undersea.

The new thinking from Chinese experts to search for oilfields in the shallow sea area around 1,000 meters deep has produced good results, including the 1998 discovery of Qinghuangdao 32-6 oilfield with reserves of 170 million tons.

Producing 160 million tons of oil annually, China is the fifth largest oil producer in the world.

However, according to a report issued by 60 research institutes and ministries, China will face a shortage of 600 million tons of oil by the year 2050 if the economy continues to develop at its current pace.

The country's oil reserve is 94 billion tons, with most found in land areas. But the output of many of the land oilfields has been dropping. Since 1979, China has cooperated with more than 50 foreign companies in exploring offshore oil.

Chinese scientists and Phillips will continue their cooperation to step up the exploitation in the new oilfield, which is expected to boost the yearly oil output of all existing Bohai Sea oil fields to more than ten million tons in the coming years, said geologist Deng.