--> Abstract: Recent Significant Discoveries in Mature Basins – Take Offshore Bohai Bay Basin as an Example, by Zhu Weilin, Xia Qinglong, and Zhou Xinhuai; #90124 (2011)

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Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA

Recent Significant Discoveries in Mature Basins – Take Offshore Bohai Bay Basin as an Example

Zhu Weilin1; Xia Qinglong2; Zhou Xinhuai2

(1) China National Offshore Oil Corp., Beijing 100010,P.RChina, Tianjin, China.

(2) Tianjin Branch of China National Offshore Oil Company Ltd., Tianjing, China.

The Bohai sea area is the offshore part of the Bohai Bay Basin. The drilling of the first new field wildcat dated back to 1966 and the discovery peak occurred during 1995-2000 when a number of major heavy oil fields with an initial oil in place of over 100 million tons had been found. They include PL19-3, QHD32-6, CFD11-1, BZ25-1S fields. By the end of 2004, about 2.7 billion cubic meters of oil in place had been found in the offshore Bohai Bay Basin. With increasing exploration maturity, however, it has become more and more difficult to make new significant discoveries. Maintaining a highly efficient and sustainable petroleum exploration venture have met serious challenges.

Since 2005, systematic studies of effective source kitchens, high-quality reservoirs distribution and oil/gas migration patterns indicated that the Tan-Lu strike-slip fault zone and the slopes surrounding the Bozhong depression were the prospective areas for petroleum enrichment. The exploration in the offshore Bohai Bay basin entered a new exploration phase which was characterized by exploration for oil and gas in multiple stratigraphic intervals and targeting multiple types of traps. The exploration focused on traps rich in oil and gas and meanwhile the prospectivity of the areas surrounding these traps were quickly and thoroughly assessed.

The JZ25-1, JX1-1, BZ28-34, KL10-1 trends and the eastern plunging end of the Shi-Jiu-Tuo arch were selected for drilling. The exploration results proved that all the five trends are petroleum enrichment belts. The fields newly found in the trends led to the second peak of petroleum discovery in the offshore Bohai Bay basin. About 1.6 billion cubic meters of oil in place had been discovered in five years. Recent discoveries have been made in new plays and new domains which include the Neogene litholgic traps, steep slope zones of depressions, and fault transfer zones. The occurrence of second discovery peak indicates that new exploration ideas and technological innovations have played an important role in petroleum exploration in mature basins. Exploration in China's offshore areas and similar basins may take lessons and guidance from the successful exploration practice in the offshore Bohai Bay Basin.