On the 18th, it was learned from China National Offshore Oil Corporation (CNOOC) that another billion ton discovery was made in the central and northern waters of the Bohai Sea in China - the Qinhuangdao 27-3 oilfield, with a proven geological oil reserve of 104 million tons. This is the second major oil and gas discovery in the sea area after a 10-year hiatus. The Qinhuangdao 27-3 oilfield is located in the central northern sea area of the Bohai Sea, about 200 kilometers west of Tianjin City, with an average depth of about 25 meters. The discovery well Qinhuangdao 27-3 encountered an oil layer of 48.9 meters during drilling, with a completed drilling depth of 1570 meters. After testing, the daily crude oil production of a single well in the oilfield is about 110 tons, showing good exploration prospects. "According to normal mining, the Qinhuangdao 27-3 oilfield can extract nearly 20 million tons of crude oil. After being refined into gasoline, it can meet the daily transportation needs of urban residents with a population of millions for more than 10 years. The extracted asphalt can lay over 100000 kilometers of 4-lane highways, which is equivalent to more than 3 orbits around the world." Zhou Jiaxiang, Deputy General Manager of CNOOC Tianjin Branch, introduced. The discovery of Qinhuangdao 27-3 oilfield is another important practice in the exploration of shallow lithology in the Bohai Sea. The Shijiutuo Uplift, where it is located, was one of the main battlefields for early exploration in the Bohai Oilfield. Researchers used the idea of structural exploration to search for high positions of structural traps and deployed wells. Three large and medium-sized oil fields, including the Qinhuangdao 32-6 oilfield, were discovered in these high positions. However, since 2011, drilling in areas with high exploration advantages has been almost exhausted, and the enrichment patterns of oil and gas in low areas are not yet clear. After multiple rounds of structural exploration, the results have not been ideal. To overcome the exploration dilemma, Chinese offshore oil researchers have drawn on the successful experience of exploring Kenli 6-1 and Kenli 1-2 billion ton lithological oil fields, gradually transforming the exploration approach from traditional structural exploration to lithological exploration. They combined a large amount of drilling data and experiments to successfully prove that the low part of the protrusion also has the ability to store oil and gas, changing traditional understanding. The final researchers conducted solid basic research on sedimentation, geochemistry, and other aspects to identify the complex strike slip fault zone enriched in oil and gas in Shijiutuo, achieving a major discovery of a billion ton oil field in the exploration of the old area. Xu Changgui, Deputy Chief Engineer of CNOOC Exploration, said that the Qinhuangdao 27-3 oilfield is the sixth billion ton oilfield discovered consecutively in Bohai Oilfield since 2019. The successful discovery of this oilfield further confirms the vast oil and gas exploration prospects of the complex strike slip fault zone in Bohai. (Lai Xin She)