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The AAPG/Datapages Combined Publications Database
AAPG Bulletin
Abstract
AAPG Bulletin, V.
Upper Oligocene lacustrine source rocks and petroleum systems of the northern Qaidam basin, northwest China
Andrew D. Hanson,1 Bradley D. Ritts,2 David Zinniker,3 J. Michael Moldowan,4 Ulderico Biffi5
1Department of Geological and Environmental Sciences, Stanford University, Stanford, California, 94305-2115; current address: Department of Geoscience, University of Nevada Las Vegas, 4505 Maryland Parkway, Las Vegas, Nevada, 89154; email: [email protected]
2Department of Geological and Environmental Sciences, Stanford University, Stanford, California, 94305-2115; current address: Department of Geology, Utah State University, 4505 Old Main Hill, Logan, Utah, 84322-4505; email: [email protected]
3Department of Geological and Environmental Sciences, Stanford University, Stanford, California, 94305-2115; email: [email protected]
4Department of Geological and Environmental Sciences, Stanford University, Stanford, California, 94305-2115; email: [email protected]
5Agip, 20097 San Donato, Milan, Italy
AUTHORS
Andrew Hanson attained a B.S. degree in nursing from Montana State University, an M.S. degree in geological sciences from San Diego State University, and a Ph.D. in geological and environmental sciences from Stanford University. His dissertation focused on organic geochemistry, petroleum geology, and tectonics and sedimentation of the Tarim and Qaidam basins in northwest China. After graduation he worked for Texaco Exploration investigating deep-water areas offshore Nigeria. Hanson recently joined the faculty of the University of Nevada, Las Vegas and is establishing research projects in China and the western United States.
Bradley Ritts received his Ph.D. in geological sciences from Stanford University, where he worked on tectonics, sedimentology, and petroleum systems of the Qaidam and Tarim basins. He then moved to Chevron Overseas Petroleum, as an exploration geologist working on China. Ritts is an assistant professor at Utah State University, where his research focuses on tectonics and sedimentation and petroleum systems of tectonically active, nonmarine basins. His current research projects are in China and the western United States.
David Zinniker is a Ph.D. candidate in the department of Geological and Environmental Sciences at Stanford University. His work focuses on the use of molecular organic geochemistry, stable isotope geochemistry, and micropaleontology to understand ancient terrestrial ecosystems and petroleum that has significant higher plant input. He received his B.S. degree in geology at Stanford University in 1996.
J. Michael Moldowan attained a B.S. degree in chemistry from Wayne State University (1968) and a Ph.D. in chemistry from the University of Michigan (1972). After a postdoctoral fellowship with Carl Djerassi at Stanford University, he joined Chevron in 1974 where he developed fundamental and applied technology related to petroleum biomarkers. Since 1993, Moldowan has been professor (research) in Stanford University's Department of Geological and Environmental Sciences. He has published more than 80 journal articles and three books. Two articles, published in 1978 and 1989, received best paper awards from the Organic Geochemistry Division of the Geological Society.
Ulderico Biffi graduated from the University of Milan's Geological Sciences department. He joined AGIP in 1977 and studied Tertiary palynomorphs of the Niger Delta. He has conducted original palynological studies of the Mesozoic Nubian Sequence in Libya, the Mesozoic stratigraphy of the Tarim basin, the Tertiary Numidic basin in Sicily, and the Italian Paleogene and Neogene. Currently he is involved in the study of the Caspian Neogene.
ACKNOWLEDGMENTS
Primary financial support for this article was provided by the Stanford China Industrial Affiliates. Additional funding was provided by the Shell and McGee Funds of Stanford University and student grants from the AAPG Grants-in-Aid Program and the Geological Society of America. The Stanford Molecular Organic Geochemistry Industrial Affiliates supported biomarker studies. David Zinniker and J. Michael Moldowan acknowledge partial research support from ACS-PRF Grant #30245-AC2. Ching-Yen Chu provided excellent translation and field assistance. Edmund Chang arranged logistics and provided translation. Alan Carroll (formerly with Exxon Production Research [EPR] Corporation) arranged for analytical work that was completed at Humble Geochemical with expenses being covered by EPR.
ABSTRACT
Our organic geochemical study of oils from the northern Qaidam basin defines a family of genetically related oils that contain biomarkers indicative of source rocks deposited in Tertiary hypersaline, anoxic lacustrine settings. Although Cenozoic outcrop samples from northern Qaidam are too organic lean to be of source quality, dark laminated upper Oligocene mudstones containing gypsum crystals and pyrite from the Shi 28 well yield total organic carbon (TOC) and Rock-Eval data indicative of fair to good source rocks. Organic matter is derived from algae and bacteria and there apparently was little contribution from terrestrial material. Biomarker data provide a good correlation between the produced oils and the upper Oligocene Shi 28 core samples. Hydrocarbons derived from these source rocks are contained in upper Oligocene, Miocene, and Pliocene reservoirs. Although eight of the oil samples are from the northwest corner of the basin, one sample in this genetic family of hypersaline oils comes from northeast Qaidam, an area previously believed to only produce oils derived from Jurassic freshwater lacustrine source rocks. This sample thus indicates the presence of an unidentified and undocumented source rock in the northeast part of the basin. Hypersaline oils and the associated source rocks have low biomarker maturity parameters. Thermal 
modeling
indicates that hydrocarbon generation probably occurred in northwestern Qaidam within the last 3 million years.
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