Publication Date:
2008-09-01
Description:
Hydrocarbon-bearing zoned calcite cements occur widely in Jurassic–Cretaceous fault-zone cores and sandstone outcrops of the northwestern Junggar Basin (northwest China). Hydrocarbon-bearing bands alternate with nearly hydrocarbon-free bands at a micron scale. Analytical results from biomarker organic geochemistry, Fourier transform infrared microspectroscopy, and trace-element geochemistry on these zoned cements suggest that at least three different types of fluids have participated in their formation. The first fluid type is probably primary, unmodified lacustrine formation water, from which the hydrocarbon-poor bands are formed and are characterized by Mg-rich calcite. The other two types of fluids include basinal fluids (e.g., hot hydrocarbon-bearing fluids) and meteoric water. The hydrocarbon-rich bands in which the hydrocarbons have been biodegraded and the Mn content is relatively high suggest a mixture of hydrocarbon-bearing basinal fluid and meteoric water. The alternating growth of hydrocarbon-bearing and hydrocarbon-free bands of calcite cements implies that the cement formation is episodic; it is related to alternating episodes of mixed petroleum-bearing fluid and unmodified primary formation waters, respectively. The fault appears to have been a mixing zone where seismic pumping during the movement of associated regional faults occurred. Thus, in the northwestern Junggar Basin, the micron-scale hydrocarbon-bearing zoned structure of the calcite cements is likely a reflection of episodic petroleum fluid migration in fault zones. Zhijun Jin got his Ph.D. in 1992 from Gubkin Russian State University of Oil and Gas. He was the vice president of China Petroleum University in 1998, in charge of the Research and Development project management. In 2002, he was transferred to SINOPEC as the president of SINOPEC Exploration and Production Research Institute. In 2006, he began to take another responsibility as the deputy chief geologist of SINOPEC. Because of his strong scientific enthusiasm, he has been involved in many petroleum exploration and production research projects and has also been assigned as the chief scientist for the national geoscientific projects. His interests are in the study of basin and geofluids analysis, petroleum migration and accumulation in the carbonate reservoirs, and petroleum resource assessment of superimposed basin. Jian Cao received his Ph.D. in petroleum geology from Nanjing University (2005). His current research interests include petroleum migration in fault-zone areas and trace-element geochemistry during water-rock interaction in sedimentary basins. Wenxuan Hu received his Ph.D. from the China University of Geosciences (Beijing) (1988). He is now a professor of economic geology at Nanjing University. He has conducted petroleum geology studies in several Chinese basins, including the Bohai Bay, Junggar, and Tarim basins. His interest is now in the study of geologic fluids and their activity in mineral and petroleum formation. Yijie Zhang obtained his B.S. degree (1984) and his M.S. degree (1990) in stratigraphy and paleobiology from the China University of Geosciences (Wuhan), and he received his Ph.D. in petroleum geology from the China University of Petroleum (2001). His interests are in the study of petroleum formation and resource assessment of Chinese sedimentary basins. Suping Yao received his Ph.D. from the China University of Mining and Technology (1990). He is now a professor of geochemistry at Nanjing University. His interest is in the study of organic petrology and geochemistry of coals and organic-rich source rocks. Xulong Wang received his Ph.D. in petroleum geology from the Southwest Petroleum University, China (2001). His is now the chief geologist of PetroChina Xinjiang Oilfield Company. He has led many research projects in hydrocarbon formation and exploration in the Junggar Basin. Currently, his interest is in the study of petroleum geology and geochemistry in lacustrine fault basins. Yueqian Zhang received his M.S. degree in petroleum geology from the China University of Petroleum (2000). His is now the head of the exploration branch of the Research Institute of Exploration and Development, PetroChina Xinjiang Oilfield Company. His interests are in the study of Carboniferous-source-derived petroleum formation and exploration in the Junggar Basin. Yong Tang received his M.S. degree in petroleum geology from the Southwest Petroleum University, China (1999). His interest is the study of petroleum accumulation and exploration in the northern Junggar Basin. Xinpu Shi received his B.S. degree in petroleum geology from the Chengdu University of Science and Technology, China (1988). His recent interest is in the study of petroleum accumulation in the central Junggar Basin.
Print ISSN:
0149-1423
Electronic ISSN:
1943-2674
Topics:
Geosciences
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