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Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Natural Gas Exploration Potential of BaiYun Depression, South China Sea: Implications from Gas Carbon Isotope Kinetic Modeling of Recent Discovered Gas Reservoirs
(1) SKLOG, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China.
(2) Department of Earth Science, Zhejiang University, Hangzhou, China.
(3) Research Institute, CNOOC China Limited Shenzhen, Guangzhou, China.
Deepwater is one of the most active and the most attractive petroleum exploration targets worldwide over last two decades. In China, it was mainly located in the South China Sea and the deepwater exploration area in the northern continental margin of South China Sea has an approximately 750,000 km2. The recent discovery of Liwan 3-1 gas field and others in the Baiyun depression, South China Sea suggested a huge potential of being gas province, and making South China Sea a blooming exploration region.
Previous studies showed that there are three potential Tertiary source strata, namely the Wenchang Formation, the Enping Formation and the Zhuhai Formation, making possible contributions to oil and gas accumulations in the Baiyun depression, South China Sea. Source rocks from the Wenchang Formation are oil prone, whereas source rocks from the Enping Formation and Zhuhai Formation are gas prone. In this communication, using gas carbon isotope kinetic modeling, the processes involved in the formation of gas pools from the discovered gas reservoirs were investigated within geological context and try to figure out the source kitchen distribution and its generation and accumulation history. Three gas fields were selected and the results indicated that all the three gas fields shared a common characteristic. These include: (1) the source rock from the Enping Formation is the main contributor to the discovered gas field although it is still ambiguous for the Enping Formation with respect to its depositional facies and distributions in the Baiyun depression due to deep buried and few well penetrated; (2) the match between the maturity of source rocks and formation of traps is the main factor to control whether it can be an effective source kitchen; (3) the effective source kitchen is normally located near gas field; and (4) the filling history delineation demonstrated that the main charging took place from the recent 15Ma to present for the discovered gas pools. The results suggest that exploration potential in the Baiyun depression, South China Sea strongly depends upon the distribution of Enping source strata and its thermal history experienced, and a successful play must be a well match between formation of traps and the maturity of source rock near traps.