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C H I N A P E T R O L E U M E X P L O R A T I O N Development and Application of Exploration Portfolio Systems of CNOOC/Mi Lijun 1, Zhang Houhe 2, Chen Rong 2, Wu Jingfu 2 // 1. CNOOC Exploration Department, Beijing 100010; 2. CNOOC Research Center, Beijing 100027 Abstract: The portfolio optimizing technology is a hot spot of the international petroleum study, while the exploration portfolio system is an important tool to support the implementation of exploration strategies and the planning of exploration allocation of the company. Based on systematic research on portfolio optimization methods, an exploration portfolio system featuring in advanced technologies and perfect function is developed in CNOOC. The system can be used for the economic evaluation of exploration targets, the single-target and multischeme selection, the multi-target synthetic queuing, the zone economic evaluation, and the optimization of exploration portfolio. It helps to realize the integration of the economic evaluation of exploration targets and zones and the research of portfolio and to enrich them. And the evaluating process can be more applied to offshore exploration and development. The system can be widely used in the evaluation of exploration targets, the annual combination of drilling targets, the seasonal drilling allocation, and the rolling planning. Key words: CNOOC; exploration target; exploration zone; economic evaluation; scheme selection; portfolio Empirical Analysis on Marginal Output of Oil and Gas Exploration/Luo Zuoxian//Petroleum Exploration and Production Research Institute, Sinopec, Beijing 100083 Abstract: During exploration and production, the discovery of oil and gas reserves can be considered to be the result of 2D seismic work, 3D seismic work, and well exploration. When the contribution of exploration to reserves discovery is measured, an oilfield in China is selected as a case. A regressive model is established, taking the proved reserves as dependent variables and the exploration obligation as independent variables. Besides, the other regressive model is established, taking the exploration obligation as dependent variables and the 2D and 3D seismic work as independent variables. On the basis of the regression coefficient obtaining from the two models, the contribution rate of 2D and 3D seismic work is measured and calculated comprehensively. The contribution rate of exploration obligation to reserves discovery can be seen as the basis for making investment decisions and deploying work in oilfields. Key words: oil and gas reserves; 2D seismic; 3D seismic; well exploration; regressive model Research on Sedimentary Features and Heterogeneity of Reservoir B in Kuman Oilfield, Volga Basin/Yang Shuang 1, 2, Yu Junmin 1, Zhao Quanguo 3, Li Guobin 1 //1 China University of Geosciences, Beijing 100083; 2 Exploration & Production Research Institute, Sinopec, Beijing 100083; 3 Logging Company of PetroChina Huabei Oilfield Company, Renqiu City, Hebei Province 062552 Abstract: Reservoir B is the major oil production zone of Kuman Oilfield in Volga Basin, of which the oil in place accounts for 48.5% of the total. Research on the sedimentary features and heterogeneity of the reservoir is conducted, using the drilling, logging, and core data. Results show that the reservoir is tide delta and tide-delta sedimentary facies. The major oil layer (C1- andc1- ) is dominated by dune ridges, while the non-major one is dominated by tidal channels, mudflat facies, and sandflat facies. The reservoir permeability variation coefficients range from 0.42 to 1.62, and the mutation coefficients are between 1.87 and 6.69. The permeability ratio is higher. The interlayer heterogeneity and the inner heterogeneity are strong, while the plane heterogeneity is weaker. Comprehensive evaluation shows that the C1- and C1- yers la feature in stable plane distribution and good connectivity, and they are favorable for development. The C1-, 1- C, and C1- yers la feature in severe heterogeneity, small petroliferous area, and thin oil layers, and they are unfavorable for development. Key words: Volga Basin; Kuman Oilfield; B reservoir; sedimentary feature; heterogeneity Analysis of Influencing Factors on Hydrocarbon Discoveries in Paleozoic Hydrocarbon Basins, Libya/Lu Jingmei, Huang Xingwen// International Research Department of CNOOC Research Center, Beijing 100027 Abstract: There are six hydrocarbon basins in Libya, in which four are Paleozoic hydrocarbon basins, i.e., the Ghadamis Basin, the Murzuq Basin, the Kufra Basin, and the Cyrenaica Basin. The proved reserves of the basins account for 9% of the total in the whole country. Other reserves centralize in Mesozoic and Cenozoic basins. Based on the study of the exploration history of the oilfields and basins with hydrocarbon discoveries, three factors influencing Paleozoic hydrocarbon discoveries are recognized, namely, the petroleum geology conditions, the exploration degree, the world situation and national policies. The petroleum geology condition is the most critical one. Ghadamis and Murzuq basins have favorable petroleum geology conditions among the four basins. In recent years, the relationship between Libya and U. S. is much better than before and the national policies are favorable, so the exploration investment in Paleozoic basins, especially in the Murzuq Basin, increase a lot, and new discoveries are made increasingly. The Paleozoic basins are becoming hot spots in exploration, and they should be paid more attention by Chinese oil companies. Key words: Libya; Paleozoic; hydrocarbon basin; exploration history; hydrocarbon discovery; influencing factor