The Ministry of Land and Resources recently confirmed that the Puguang Gas Field in Southeast China's Sichuan Province has become the country's second largest, with verified reserves reaching 356.072 billion cubic meters.

It is the first large-scale gas field China has found in its marine strata, experts said. Over the past several decades, major oil and gas fields have been discovered only in the continental strata.

Ma Yongsheng, vice-manager of the Southern Exploration and Production Company, part of the China Petroleum and Chemical Corporation, said the field, which is located in Xuanhan County in the northeast of Sichuan Province, has huge potential and its ultimate reserves will be gigantic.

"Our company has so far drilled more than 20 wells in the field with none of them falling through, which is uncommon," Ma was quoted by CCTV as saying.

Liu Guangding, an academic and researcher with the Chinese Academy of Sciences' Institute of Geology and Geophysics, said the Puguang Gas Field marked a technological breakthrough for China's oil and gas exploration.

"In the past, China's exploration of oil and gas has focused on the continental strata," Liu said. "But the marine strata, which have previously been neglected, have far greater oil and gas reserves."

Liu projected more major oil and gas fields would be detected in China's vast marine strata, such as the Tarim Basin in the Xinjiang Uygur Autonomous Region, the Ordos in the Inner Mongolia Autonomous Region and the Sichuan Basin.

"About 70 to 80 percent of China's oil and natural gas resources have not yet been detected," Liu said. "The new oil and gas fields in the marine strata will greatly ease China's shortage of oil and natural gas."

Ninety percent of the world's verified oil and gas reserves lie in the marine strata and China has 4.5 million square kilometers of them, which accounts for almost half of its total land area, sources said.

China's largest gas field, the Sulige Gas Field in the Inner Mongolia Autonomous Region, has verified reserves of 533.6 billion cubic meters and went into production last year.

China became an oil importing country in 1993.