Lower-Middle Jurassic Nonmarine Source Rocks and Petroleum Systems of the Northern Qaidam Basin, Northwest China
Lower-Middle Jurassic Nonmarine Source Rocks and Petroleum Systems of the Northern Qaidam Basin, Northwest China
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DOI：
10.1306/e4fd4661-1732-11d7-8645000102c1865d
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发表时间：
1999-12
期刊：
影响因子：
3.5
通讯作者：
B. Ritts;A. Hanson;D. Zinniker;J. Moldowan
中科院分区：
文献类型：
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作者：
B. Ritts;A. Hanson;D. Zinniker;J. Moldowan
柴达木盆地是青藏高原东北缘的一个陆相含油气盆地。第三系盐湖相沉积和侏罗系淡水湖相或陆相地层是有利的烃源岩。侏罗系烃源岩在沉积体系、岩性、时代和有机地球化学方面与中亚许多盆地（包括塔里木、准噶尔等重要产油盆地）的陆相侏罗系烃源岩相似。这些侏罗系烃源岩在早、中侏罗世沉积于陆内前陆型盆地的淡水湖泊体系中。这些湖相地层与煤和含煤泥岩有关，可能是次要的烃源岩。根据沉积环境的分子标志物和时代标志物，柴达木盆地北方原油可分为两类：一类为侏罗系淡水湖相烃源岩，另一类为第三系高盐湖相烃源岩。柴达木盆地部分原油与侏罗系油源的对比建立了一个包括这些非海相侏罗系烃源岩的含油气系统。该含油气系统的原油产自柴东北部背斜和逆冲断层相关圈闭的第三系和中生界储层。侏罗系烃源岩成熟度模拟表明，柴达木北方大部分地区的原油生成和排出时间为中新世-上新世。盆地的地质背景表明，盆地内的排水主要是垂直的，可能主要是沿着断层，直到在上覆的新生代剖面中遇到蒸发岩或超压页岩盖层。该含油气系统的文献资料表明，柴达木北方和西南部的其他勘探目标仍然被低估;此外，北方柴达木含油气系统是一个有用的类比，可以解释类似侏罗纪烃源岩在其他文献稀少的中亚盆地中的作用。
The Qaidam basin is a nonmarine, petroliferous basin on the northeastern margin of the Tibet Plateau. Potential source rocks are reported from Tertiary saline lacustrine deposits and Jurassic freshwater lacustrine or terrestrial strata. The Jurassic source rock is similar, in terms of depositional system, lithology, age, and organic geochemistry, to nonmarine Jurassic rocks that are thought to be potentially significant hydrocarbon sources in many basins of central Asia, including the Tarim, Junggar, and other important petroleum-producing basins. These Jurassic source rocks were deposited in freshwater lacustrine systems in intracontinental foreland-style basins during the Early and Middle Jurassic. These lacustrine strata are associated with coals and coaly mudstones with possible secondary importance as hydrocarbon source rocks. Oils from the northern Qaidam basin can be divided into two groups based on molecular indicators of depositional environment and age-diagnostic biomarkers: those derived from this Jurassic freshwater lacustrine source rock and those derived from a Tertiary hypersaline lacustrine source rock. The correlation of some Qaidam oils to a Jurassic source establishes a petroleum system involving these nonmarine Jurassic source rocks. Oils of this petroleum system have been produced from Tertiary and Mesozoic reservoirs in anticlinal and thrust-related traps in northeastern Qaidam. Maturation modeling of the Jurassic source rock indicates that these oils were generated and expelled during the Miocene-Pliocene in much of northern Qaidam. The geological context of the basin suggests that drainage within the basin primarily was vertical, probably mainly along faults, until evaporite or overpressured shale seals were encountered in the overlying Cenozoic section. Documentation of this petroleum system suggests other exploration targets remain underevaluated in northern and southwestern Qaidam; furthermore, the northern Qaidam petroleum system is a useful analog to interpret the role of similar Jurassic source rocks in other, sparsely documented, basins of central Asia.