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1.
Geochemical characterisation of 18 crude oils from the Potwar Basin (Upper Indus), Pakistan is carried out in this study. Their relative thermal maturities, environment of deposition, source of organic matter (OM) and the extent of biodegradation based on the hydrocarbon (HC) distributions are investigated. A detailed oil-oil correlation of the area is established. Gas chromatography-mass spectrometry (GC-MS) analyses and bulk stable carbon and hydrogen isotopic compositions of saturated and aromatic HC fractions reveals three compositional groups of oils. Most of the oils from the basin are typically generated from shallow marine source rocks. However, group A contains terrigenous OM deposited under highly oxic/fluvio-deltaic conditions reflected by high pristane/phytane (Pr/Ph), C30 diahopane/C29Ts, diahopane/hopane and diasterane/sterane ratios and low dibenzothiophene (DBT)/phenanthrene (P) ratios. The abundance of C19-tricyclic and C24-tetracyclic terpanes are consistent with a predominant terrigenous OM source for group A. Saturated HC biomarker parameters from the rest of the oils show a predominant marine origin, however groups B and C are clearly separated by bulk δ13C and δD and the distributions of the saturated HC fractions supporting variations in source and environment of deposition of their respective source rocks. Moreover, various saturated HC biomarker ratios such as steranes/hopanes, diasteranes/steranes, C23-tricyclic/C30 hopane, C28-tricyclic/C30 hopane, total tricyclic terpanes/hopanes and C31(R + S)/C30 hopane show that two different groups are present. These biomarker ratios show that group B oils are generated from clastic-rich source rocks deposited under more suboxic depositional environments compared to group C oils. Group C oils show a relatively higher input of algal mixed with terrigenous OM, supported by the abundance of extended tricyclic terpanes (up to C41+) and steranes.Biomarker thermal maturity parameters mostly reached to their equilibrium values indicating that the source rocks for Potwar Basin oils must have reached the early to peak oil generation window, while aromatic HC parameters suggest up to late oil window thermal maturity. The extent of biodegradation of the Potwar Basin oils is determined using various saturated HC parameters and variations in bulk properties such as API gravity. Groups A and C oils are not biodegraded and show mature HC profiles, while some of the oils from group B show minor levels of biodegradation consistent with high Pr/n-C17, Ph/n-C18 and low API gravities. 相似文献
2.
Q. Yuan 《Australian Journal of Earth Sciences》2018,65(5):727-738
The molecular composition of Carboniferous–Permian coals in the maturity range from 0.66 to 1.63% vitrinite reflectance has been analysed using organic geochemistry to investigate the factors influencing the biomarker compositions of humic coals. The Carboniferous–Permian coal has a variable organofacies and is mainly humic-prone. There is a significant difference in the distribution of saturated and aromatic hydrocarbons in these coals, which can be divided into three types. The Group A coals have biomarker compositions typical of humic coal, characterised by high Pr/Ph ratios, a lower abundance of tricyclic terpanes with a decreasing distribution from C19 tricyclic terpane to C24 tricyclic terpane and a high number of terrigenous-related biomarkers, such as C24 tetracyclic terpane and C29 steranes. The biomarker composition of Group B coals, which were deposited in a suboxic environment, have a higher abundance of rearranged hopanes than observed in Group A coals. In contrast, in Group C coals, the Pr/Ph ratio is less than 1.0, and the sterane and terpane distributions are very different from those in groups A and B. Group C coals generally have abnormally abundant tricyclic terpanes with a normal distribution maximising at the C23 peak; C27 steranes predominates in the m/z 217 mass fragmentograms. The relationships between biomarker compositions, thermal maturity, Pr/Ph ratios and depositional environments, indicate that the biomarker compositions of Carboniferous–Permian coals in Ordos Basin are mainly related to their depositional environment. This leads to the conclusion that the biomarker compositions of groups A and B coals collected from Shanxi and Taiyuan formations in the northern Ordos Basin are mainly related to their marine–terrigenous transitional environment, whereas the biomarker compositions for the Group C coals from Carboniferous strata and Shanxi Formation in the eastern Ordos Basin are associated with marine incursions. 相似文献
3.
为明确白云凹陷目前发现原油的成因及来源,系统分析取自珠江口盆地不同类型原油中各类生物标志物的分布与组成特征,发现番禺低隆起北部构造及番禺4洼的原油具有姥植比低(2.0),指示陆源有机质输入的奥利烷含量中等,基本缺乏达玛树脂贡献的双杜松烷,各类重排构型甾藿含量较低,而指示沟鞭藻贡献的C_(30)4-甲基甾烷异常丰富的特点。C_(30)4-甲基甾烷与C_(29)规则甾烷的比值2.1,且其三环萜烷系列C_(19-26)呈现以C_(21)为主峰的正态分布,指示其原始生烃母质以藻类为主,表明这类原油与文昌组湖相烃源岩具有较好的可比性;而番禺低隆起南部构造及白云凹陷的凝析油具有姥植比高(4.0),明显富含奥利烷和双杜松烷,各类重排构型甾藿烷含量较高,缺乏C_(30)4-甲基甾烷的特点,且其三环萜烷C_(19-26)呈现阶梯状依次降低的特点,表明陆源有机质是其主要原始生烃母质,这符合白云凹陷发育恩平组煤系烃源岩的石油地质背景。 相似文献
4.
Terrestrial faulted lacustrine basin is considered as a favorable place for the development of source rocks,especially the fault basins in eastern China.Based on molecular composition study of saturated and aromatic hydrocarbons in the extracts of source rocks of the Yingcheng and Shahezi formations in the Lishu Fault Depression,it is revealed that the extracts of source rocks are provided with low ratio of Pr/Ph,low content of C24 tetracyclic terpanes,high content of tricyclic terpanes and gammacerane,relatively high content of C27 steranes in the sag belt and its periphery;relatively high ratio of Pr/Ph,relatively high content of tetracyclic terpanes and gammacerane,low content of C27 steranes and obvious advantages of C29 steranes in its gentle slope belt;with high ratio of Pr/Ph,high content of C19,C20 tricyclic and C24 tetracyclic terpanes,very low content of gammacerane and C27 steranes,and high content of C29 steranes in the edge of fault depression.According to the organic matter input and sedimentary environment,three types of source rocks have been established,which,respectively,are the mode of mixing organic matter input in deep and semi-deep lake,the advantage of terrigenous input in shallow lake and terrigenous input in shore-shallow lacustrine.The first mode is supposed to generate oil and gas,while the second one tends to generate oil.The distribution characteristics of oil and gas in the Lishu Fault Depression are very likely to be controlled by hydrocarbon generating characteristic of different source rock types. 相似文献
5.
基于40余个不同岩性烃源岩及原油饱和烃组分的GC/MS和GC/MS/MS分析资料,揭示了琼东南盆地崖城地区渐新统不同沉积相带烃源岩的生物标志物组合特征,并与崖城油气田原油进行油源精细对比,提出了新的认识。研究结果表明,海岸平原沼泽相煤及碳质泥岩呈姥鲛烷优势(Pr/Ph>5.0),三环萜烷以低碳数化合物为主(C19/C23>3.0),甾烷丰度低(藿烷/甾烷>5.0), C29甾烷优势显著(>60%),指示高等植物为主要的有机源,且沉积于氧化环境。浅海相泥岩中Pr/Ph值大多在1.0~2.5,表征弱还原-弱氧化环境;其三环萜烷以C21或C23为主峰,甾烷呈"V"字型分布,藿烷/甾烷比值小于3.0,具陆源和水生双重有机质生源。煤及碳质泥岩中奥利烷和双杜松烷等陆源标志物均较少,而泥岩中却普遍富含这些化合物,反映了近岸海相沉积有机质的特殊性。因而,在近海盆地地层中奥利烷和双杜松烷丰度并不能代表总体有机质中陆源的输入比例,更可能是指相标志。通过与烃源岩的分子地球化学对比表明,崖城油气田的主体原油兼具煤成烃和泥岩所生油的生物标志物组成,为混源油,来自渐新统不同沉积相带烃源岩。 相似文献
6.
The Qinjiatun and Qikeshu oilfields are new Mesozoic petroleum exploration targets in Lishu Fault Depression of Songliao Basin, northeastern China. Currently, researches on geochemistry of crude oils from Qinjiatun and Qikeshu oilfields have not been performed and the genesis of oils is still uncertain. Based on bulk analyses, the crude oils in the Qinjiatun and Qikeshu oilfields of Lishu Fault Depression from the Lower Cretaceous can be classified as three types. TypeⅠoils, from Quantou and Denglouku formations of Qikeshu oilfield, are characterized by high C24tetracyclic terpane/C26tricyclic terpanes ratios, low gammacerance/C30hopane ratios, tricyclic terpanes/hopanes ratios, C29Ts/C29norhopane ratios and 17α(H)-diahopane/17α(H)-hopane ratios, indicating a brackish lacustrine facies. TypeⅡoils, from Shahezi Formation of Qikeshu oilfield show low C24tetracyclic terpane/C26tricyclic terpanes, high gammacerance/C30hopane ratios, tricyclic terpanes/hopanes ratios, C29Ts/C29 norhopane and C30diahopane/C30hopane ratios, thus suggesting that they originated from source rocks deposited in a weak reducing brackish lacustrine environment, or clay-rich sediments. Type oilsⅢ, from some wells of Qikeshu oilfield have geochemical characteristics intermediate between those two types and may be mixture of typeⅠand Ⅱoils. 相似文献
7.
China has a number of petroliferous lacustrine sedimentary basins of varying salinity and age (mainly Eocene). A geochemical investigation has been undertaken on several oils and source rocks from the Eocene lacustrine Biyang Basin. The distributions of n-alkanes, isoprenoids, steranes, and terpanes have been studied and used to characterize the sedimentary environment of deposition, maturity, biodegradation and undertake possible correlations. The ratios of C30-hopane/gammacerane, 4-methyl-steranes/regular steranes, steranes/hopanes, C21 tricyclic/C30 hopane are proposed to be indicative of the depositional environment whereas ß-carotane appears to be a source related indicator. The geochemical data obtained in this study suggest that the major source rocks in the Biyang Basin were deposited in a saline/hypersaline depositional environment. 相似文献
8.
Geochemical characteristics of Lower Permian coal-measure source rocks in Northeast Ordos Basin 总被引：1，自引：0，他引：1
General characteristics and biomarker distributions of Lower Permian coal-measure source rocks in northeastern Ordos Bsain have been analyzed in this paper. The results show that the source rocks are type III kerogen, thermally mature, with high content of total organic carbon. The extracts of the source rock samples with different lithologies from Well Su 27 feature high Pr/Ph ratios, high C19TT and C24Te, high rearranged hopanes, a predominance of C29 sterane in regular steranes, and the absence of C30 4-methylsteranes. These data suggest that the source rocks were deposited in suboxic to oxic conditions with dominantly terrigenous higher plant input. In contrast, the source rocks from wells Shuang 1 and Yu 20, are characterized by low Pr/Ph ratios, low C19TT and C24Te, high C23TT, similar content of C27 sterane and C29 sterane, and the presence of C30 4-methylsteranes, showing that the source rocks were deposited in reducing environment with algae and/or microorganisms and terrigenous higher plant input. 相似文献
9.
10.
The Neoproterozoic–Early Cambrian time is the cradle of multicellular, eukaryotic life and thereafter metazoan life started populating the planet. Biomarkers, which record the chronicles of biotic events on Earth, have been investigated using gas chromatography–mass spectrometry from a suite of nine oil samples extracted from oil stained sediments and a crude oil of Neoproterozoic–Early Cambrian age from Bikaner-Nagaur Basin, western India. The biomarker distribution is characterized by high concentration of both tricyclic terpanes and pentacyclic hopanes. The predominance of C29 regular sterane over C27 and C28 steranes indicates green algal contribution and may imply the prominence and diversification of the same algal group. The low pristane/phytane ratio and occurrence of substantial quantity of gammacerane, monomethyl 2-methyl-2-(2,4,8-trimethyltridecyl) chroman and 1,1,7,8-tetramethyl-1,2,3,4 tetrahydrophenanthrene are indicative of stratified water column as well as anoxic and enhanced salinity condition of the environment of deposition. This paper reports for the first time the presence of methyltrimethyltridecyl chromans (MTTCs) from Neoproterozoic–Early Cambrian time. Putative C19 norsteranes, probably indicative of sponge input, are recorded in the studied samples and also reported from other infracambrian oils and sediments. Normal alkanes (n-C17 and n-C18) and isoprenoids (pristane and phytane) are highly depleted in δ13C. The overall biomarker distribution and carbon isotope data of oils from Bikaner-Nagaur Basin show similarities with those of other infracambrian oils like Huqf oils from Oman and Baykit High oils from eastern Siberia. 相似文献
11.
北部湾盆地不同凹陷原油生物标志物分布与组成特征 总被引：7，自引：1，他引：7
通过对取自北部湾盆地不同凹陷典型原油样品中各类生物标志物的分布与组成特征的系统分析，发现盆地北部的涠西南凹陷和乌石凹陷所产原油具有姥植比低和奥利烷与各类重排构型生物标志物含量低，而C26+长链三环萜烷系列和C304 甲基甾烷含量高的特点，且其三环萜烷系列呈现以C23为主峰的正态分布，指示了该类原油的烃源岩沉积时水体较深，还原性相对较强，且原始生烃母质以藻类为主；而南部福山凹陷和迈陈凹陷所产的原油则具有姥植比高和奥利烷与各类重排构型生物标志物含量高的特征，而C26+长链三环萜烷系列和C304 甲基甾烷含量低，且其三环萜烷系列呈现C19—C26阶梯状依次降低，表明这类原油的烃源岩沉积时水体较浅，还原性相对较弱，且原始生烃母质中被子植物来源的陆源有机质贡献较大。由此表明北部湾盆地南北不同凹陷第三纪的沉积特征和有机质生源构成存在显著差异。 相似文献
12.
Mohammed Hail Hakimi Wan Hasiah AbdullahMohamed Ragab Shalaby 《Organic Geochemistry》2011,42(5):465-476
The Masila Basin is an important hydrocarbon province in Yemen, but the origin of hydrocarbons and their generation history are not fully understood. In this regard, 10 crude oils from different petroleum reservoir sections in the Masila Basin were characterized by a variety of biomarker and non-biomarker parameters using GC, GC-MS and stable carbon isotope techniques. Oils from the Masila Basin display pristane/phytane (Pr/Ph) ratios ranging from 1.7 to 2.0, low sulfur content, high C35 homohopane index, relatively high C27 sterane concentrations and relatively high tricyclic terpanes suggesting a marine clay source rock that was deposited in mildly anoxic to suboxic conditions with dominantly algal organic matter. C29 20S/(20S + 20R) steranes and ββ/(ββ + αα) sterane ratios indicate that the Masila oils have reached peak oil window maturity. Another related feature of these oils is the absence of 18α (H)-oleanane, which suggests a source age older than Cretaceous. The carbon isotope compositions are similar to those of the potential source rocks, which range from −25.4‰ to −28.3‰, indicating a marine environment. The new data presented in this paper suggest that the Masila oils constitute one oil family and that the oil originated from the Upper Jurassic Madbi source rock in the basin. 相似文献
13.
Molecular Records of Primary Producers and Sedimentary Environmental Conditions of Late Permian Rocks in Northeast Sichuan, China 总被引：2，自引：0，他引：2
A series of biomarkers were identified in the aliphatic and aromatic fractions of the extracts from Late Permian Dalong (大隆) and Wujiaping (吴家坪) formations in Shangsi (上寺) Section, Northeast Sichuan (四川), South China, on the basis of the analysis of gas chromatography-mass spectrometry (GC-MC). The dominance of lower-molecular-weight n-alkanes throughout the profile suggests the dominant contribution of algae and bacteria to the organics preserved in the marine section. Wujiaping Formation is characterized by the elevated contribution from algae as well as other photoantotrophs such as photosynthetic bacteria as shown by the molecular ratios of hopanes to steranes or tricyclic terpanes as well as the ratio of pristane (Pr) and phytane (Ph) to C17 and C18 n-alkanes. This is in accord with the data from the microscopic measurement on the calcareous algae. In contrast, Dalong Formation is featured by enhanced contribution from bacteria and probably terrestrial organics indicated by the enhanced C24 tetracyclic terpanes relative to tricyclic terpanes. The two formations also show a distinct discrimination in sedimentary environmental conditions including redox condition and salinity. The anoxic condition was only found in the middle of the Dalong Formation as shown by the ratios of Pr/Ph and dibenzothiophene to phenanthrene, consistent with the reported data of Mo and U. An enhancedsalinity indicated by the homohopane index is observed at the shallow Wujiaping Formation. On the basis of the composition of primary productivity and the redox condition, Dalong Formation is proposed, herein, to be potential hydrocarbon source rocks in the study site. It is notable that the topmost end-Permian is characterized by a large perturbance in both the redox condition and salinity, with oxic conditions being frequently interrupted by short-term anoxia, likely showing a causal relationship with the episodic biotic crisis across the Permian-Triassic boundary. 相似文献
14.
通过采集鄂尔多斯盆地西南缘4个剖面奥陶系马家沟群碳酸盐岩和平凉组泥页岩样品,对其中可溶有机质饱和烃与芳烃组分进行GC-MS分析,对比研究了马家沟群碳酸盐岩和平凉组泥页岩生物标志化合物特征。结果表明,马家沟群与平凉组正构烷烃分布形式及峰型特征、生物标志化合物参数Pr/Ph、伽马蜡烷/C30-αβ藿烷、C20-29三环萜烷/(C20-29三环萜烷+C27-35藿烷),以及甲基菲指数(MPI)均存在明显差异,这些差异反映了其沉积环境与成熟度的不同,对于马家沟群与平凉组来源油的识别具有参考价值。马家沟群正构烷烃分布形式与甾/藿比值以及C28/C29ααα20R甾烷比值之间的对应关系,反映了母质输入的细微差别。Ts/(Ts+Tm)与伽马蜡烷/C30-αβ藿烷比值之间的关系,C29甾烷αββ/(αββ+ααα)比值变化与重排藿烷与重排甾烷丰度的关系,反映上述成熟度参数明显受沉积环境影响。 相似文献
15.
S. Aboglila K. Grice K. Trinajstic D. Dawson K.H. Williford 《Organic Geochemistry》2010,41(12):1249-1258
Biomarker ratios, together with stable carbon (δ13C) and hydrogen (δD) isotopic compositions of individual hydrocarbons have been determined in a suite of crude oils (n = 24) from the East Sirte Basin to delineate their sources and respective thermal maturity. The crude oil samples are divided into two main families (A and B) based on differences in source inputs and thermal maturity. Using source specific parameters including pristane/phytane (Pr/Ph), hopane/sterane, dibenzothiophene/phenanthrene (DBT/P), Pr/n-C17 and Ph/n-Cl8 ratios and the distributions of tricyclic and tetracyclic terpanes, family B oils are ascribed a marine source rock deposited under sub-oxic conditions, while family A oils have a more terrigenous source affinity. This genetic classification is supported by the stable carbon isotopic compositions (δ13C) of the n-alkanes. Using biomarker maturity parameters such as the abundance of Pr and Ph relative to n-alkanes and the distribution of sterane and hopane isomers, family A oils are shown to be more thermally mature than family B oils. The contrasting maturity of the two families is supported by differences between the stable hydrogen isotopic compositions (δD) of Pr and Ph and the n-alkanes, as well as the δ13C values of n-alkanes in their respective oils. 相似文献
16.
对渤海湾盆地一系列生物降解原油的色谱-质谱分析结果表明,庙西凹陷PL15-8D与PL9-4井四个严重生物降解原油三环萜烷系列分布较为异常,主要表现为以C23为主峰的后峰型、C20与C23为主峰的微弱双峰型以及以C20与C24为主峰的双峰型分布模式。强烈的生物降解作用导致C19~C23三环萜烷优先于C24+三环萜烷被不同程度地侵蚀,是形成这一异常分布的根本原因。三环萜烷系列相对丰度与绝对浓度的变化规律表明,不同碳数三环萜烷的生物降解作用同时发生,但其降解速率有明显差别,即抗生物降解能力不同。三环萜烷系列化合物（除C20三环萜烷以外）的抗生物降解能力具有随碳数增加而增强的趋势,而C20三环萜烷抗降解能力似乎强于C21~C23三环萜烷。原油中未检测到脱甲基三环萜烷,表明三环萜烷的降解并非通过微生物的脱甲基化作用,推测其降解途径是微生物氧化三环萜烷C环支链末端的甲基,形成对应的羧酸化合物。四个原油样品甾烷、藿烷与三环萜烷被微生物严重侵蚀,不能用于油源对比研究,而三芳甾烷未受生物降解影响,可作为研究区严重生物降解原油油源对比的有效指标。 相似文献
17.
羌塘盆地昂达尔错地区油苗生物标志化合物特征及其指示意义 总被引：1，自引：1，他引：0
本文以油苗抽提物的饱和烃色谱-质谱分析为基础,剖析了羌塘盆地昂达尔错地区油苗的生物标志化合物特征,探讨了其沉积环境和成熟度指示意义。昂达尔错油苗含有丰富的正构烷烃、类异戊二烯烃、萜类化合物和甾类化合物。正构烷烃轻烃组分含量较高,无明显的奇偶优势。Pr/Ph比小于1,显示一定的植烷优势。萜类化合物中五环三萜烷相对含量最高,四环萜烷含量最少,并有一定的伽马蜡烷和升藿烷分布。规则甾烷相对含量为C27C29C28,呈不对称"V"字形分布,异构化成熟度参数值较高,且4-甲基甾烷化合物普遍存在。昂达尔错油苗母源岩沉积于具有较高盐度的还原环境,以藻类、菌类等海相有机质输入为主,油苗有机质处于成熟阶段。 相似文献
18.
东营凹陷南斜坡沙四下亚段—孔店组原油地球化学特征及成因分类 总被引：2，自引：0，他引：2
东营凹陷南斜坡沙四下亚段—孔店组为一套紫红色或红色碎屑岩沉积,本身不具备生烃能力,因此对该层段原油成因的研究具有重要意义。在系统分析17个油砂和5个原油样品的生物标志物组合特征的基础上,将该区原油划分为4种成因类型。Ⅰ类原油分布于平方王地区和博兴洼陷,Pr/Ph0.8,Ph/nC180.6,伽马蜡烷含量极低,4-甲基甾烷、重排甾烷含量相对高,Ts/Tm、藿烷/甾烷值相对高,可能来源于一套淡水湖相环境下形成的、富含粘土矿物的泥岩。Ⅱ类原油分布于纯化—乐安构造带、陈官庄构造带,Pr/Ph0.6,Ph/nC182,伽马蜡烷含量高,4-甲基甾烷、重排甾烷含量低,Ts/Tm和藿烷/甾烷值低,可能与一套盐湖相泥岩或灰质泥岩有成因关系。Ⅲ类原油分布于青城北缓坡构造带,检测出25-降藿烷系列,伽马蜡烷含量介于Ⅰ类和Ⅱ类之间,可能为早期充注的Ⅱ类原油遭受生物降解后和晚期充注的Ⅰ类原油形成的混源油,且以晚期充注为主。Ⅳ类原油分布于王家岗地区孔店组,具有C29甾烷绝对优势和高含量的伽马蜡烷,推断为Ⅱ类原油和一种来源于浅湖—沼泽相的原油形成的混源油。 相似文献
19.
Evaluation of the diagnostic ratios for the identification of spilled oils after biodegradation 总被引：3，自引：1，他引：2
Chuanyuan Wang Xuelu Gao Zhigao Sun Zhijiang Qin Xiaonan Yin Shijie He 《Environmental Earth Sciences》2013,68(4):917-926
Biodegradation, one of the most important weathering processes, alters the composition of spilled oil, making it difficult to identify the source of the release and to monitor its fate in the environment. A laboratory experiment was conducted to simulate oil spill weathering process of microbial degradation to investigate compositional changes in a range of source- and weathering-dependent molecular parameters in oil residues, and the conventional diagnostic ratios for oil spill identification were also evaluated. The conventional diagnostic ratios of n-alkane displayed obvious changes after biodegradation, especially for Pr/n-C17 and Ph/n-C18 with relative standard deviation more than 118.84 %, which suggests they are invalid for oil source identification of the middle-serious spill. Many polycyclic aromatic hydrocarbons (PAHs) are more resistant to biodegradation process than their saturated hydrocarbon counterparts, thus making PAHs to be one of the most valuable fingerprinting classes of hydrocarbons for oil identification. Biomarker ratios of hopanes and steranes were also useful for source identification even after moderate biodegradation, and the diagnostic ratios from them could be used in tracking origin and sources of hydrocarbon pollution. Finally, the carbon isotopic type curve may provide another diagnostic means for correlation and differentiation of spilled oils, and be particularly valuable for lighter refined products or severely biodegraded oils, the source of which may be difficult to identify by routine biomarker techniques. 相似文献
20.
各类生物标志物的组成特征表明:柴达木盆地北缘的冷湖油田原油具有姥植比高（Pr/Ph>2.0）,重排甾烷（C27重排甾烷/规则甾烷=0.5~0.7）、重排藿烷（diaC30H/C30H=0.2~0.4）和新藿烷（C29Ts/C29H=0.4~0.7）含量中等,伽马蜡烷含量低（伽马蜡烷指数<0.05）的特征,它们源于该地区发育的下侏罗统淡水湖沼相烃源岩;而柴西北区咸水湖相原油的姥植比低（Pr/Ph<0.8）,重排甾烷（C27重排甾烷/规则甾烷<0.1）、重排藿烷（diaC30H/C30H<0.05）和新藿烷（C29Ts/C29H=0.2~0.4）含量低和伽马蜡烷含量高（伽马蜡烷指数=0.4~0.8）,这一系列特征与柴西地区发育的古近系-新近系咸水湖相烃源岩一致。但是,东坪地区原油呈现完全不同的生物标志物组合,主要表现为丰富的伽马蜡烷（伽马蜡烷指数=1.2~3.0）与高含量的新藿烷（C29Ts/C29H>1.5）、重排藿烷（diaC30H/C30H>0.7）和重排甾烷（C27重排甾烷/规则甾烷>0.4）并存,这与地质样品中伽马蜡烷和重排类标志物的分布特征相矛盾,因为依据现有的认识无法解释这一特殊地球化学现象。生物标志物组成特征表明东坪地区原油所具有的特殊生物标志物组合并非源于不同类型原油之间的混合,而是一种客观存在,尽管其确切的地球化学意义和形成条件目前并不清楚。由此可见,东坪地区原油为柴达木盆地一个新的原油类型,推测其烃源岩可能形成于偏酸性的咸水环境。 相似文献