乍得Bongor强反转裂谷盆地高酸值原油成因

乍得Bongor盆地是受中非剪切带影响发育起来的中、新生代陆内强反转裂谷盆地,反转和走滑构造是盆地最显著的构造特征。所发现的原油主要为中质油(重度为20°～34°API),其次为重质油(重度小于20°API),普遍高含沥青质、高含蜡、高酸值、低含硫。为了探讨高酸值原油的成因,作者选择了该盆地15个不同酸值的原油样品,尝试应用高分辨率质谱分析原油有机酸的组成。分析结果表明,高酸值原油的有机酸主要由环烷酸组成;环烷酸碳原子数分布范围较宽,且以一环、二环、三环环烷酸为主。生物降解作用是形成高酸值原油的主要原因,而构造反转造成盆地抬升,则加速了生物降解作用的发生。     

CO_2脱沥青作用形成重油油藏的一个实例

气体的脱沥青作用是引起油藏变稠或形成沥青垫的因素之一。对苏丹ME盆地某古近系稠油油藏的地质特征、原油物性、原油溶解气组分和地球化学特征进行分析,结果显示:原油普遍具有高沥青质、高含蜡、高凝固点、高酸值和低含硫的特点;原油溶解气中CO2含量的变化与原油API度具有正相关关系;含油包裹体中含有较多的CO2。结果表明气体溶解在原油中产生的脱沥青作用是引起该油藏密度变大的主要原因;而且气体主要是无机成因的CO2,来源于邻近油藏的沟通地幔的深断裂。     

巴西桑托斯盆地油气分布特征及其成因分析

巴西桑托斯盆地油气田分布具有“外重内轻,外大内小”的分布特征.轻质油藏（原油API°介于36°～58°之间）或气藏分布于近岸水深小于1 000 m范围内,且储量较小;而水深大于1 500 m区域则主要以正常原油为主（原油API°介于25°～32°之间）,储量大.桑托斯盆地油气分布特征与盐下、盐上烃源岩性质,热演化程度以及盐岩分布有关.盐下湖相烃源岩主要为Ⅰ型有机质,倾向于生油,中央凹陷区处于高、过成熟阶段,而东部隆起带深水区域处于成熟阶段;盐上海相烃源岩主为要Ⅱ2-Ⅲ型有机质,倾向于生成轻质油和气,中央凹陷及以西区域处于油窗晚期.研究表明盐上凝析油主要来自盐上高成熟海相烃源岩的贡献;而中央坳陷北部以及以外深水区原油主要来自盐下中等成熟的优质湖相烃源岩.阐明桑托斯盆地油气分布特征及其成因,有助于深入了解桑托斯盆地成烃成藏以及油气分布规律,从而对于桑托斯盆地区块优选,降低投资风险具有重要意义.     

塔里木盆地轮南地区碳酸盐岩油气藏原油酸值的分布特征及其形成机制

轮南地区是塔里木盆地北部的主要含油气区,该地区奥陶系原油中酸值含量普遍较低,分布范围在0.01～1.41mg KOH/g,大多数原油属于低含酸原油,少数属于含酸原油或高酸原油,酸值在平面上表现出明显的"西高东低"特征。通过原油物性对比、地球化学分析及成藏过程的研究发现,原油的酸值与其母质类型、成熟度、生物降解程度及油气充注史均有一定的关系,尤其与生物降解作用密切相关。通过对原油生物标志化合物的分析,判定该区含酸原油为混合成因,这与油气成藏过程分析结果是一致的。原油中酸性物质含量会影响原油的性质,原油的酸值与物理性质具有明显的相关关系,轮南地区油气性质差异明显,具有"西油东气"的分布格局,原油的密度、胶质沥青质含量、含硫量等也具有"西高东低"的分布特点,而气油比、含蜡量等则表现为相反的分布特征。     

准噶尔盆地烃源岩与原油地球化学特征

准噶尔盆地是中国西部典型的多旋回叠合盆地,发育石炭系、二叠系、三叠系、侏罗系、白垩系和古近系6套烃源岩,广泛分布于盆地不同地区。石炭系海陆交互相烃源岩分布于盆地大部分地区,泥岩有机质丰度中等,以Ⅱ型有机质为主,碳质泥岩和煤有机质丰度高、类型差。二叠系湖相烃源岩分布广、厚度大,有机质丰度高、类型好,干酪根碳同位素组成轻,是盆地中最主要的烃源岩。三叠系湖相烃源岩在盆地东部有机质丰度较高、以Ⅱ型有机质为主。侏罗系为煤系烃源岩,有机质丰度高,但以Ⅱ_2型和Ⅲ型有机质为主,干酪根碳同位素组成重。白垩系和古近系湖相烃源岩主要分布于盆地南部,有机质丰度中等,但以Ⅰ、Ⅱ型有机质为主。石炭系烃源岩目前主要处于高—过成熟阶段,二叠系、三叠系烃源岩主要处于成熟—高成熟阶段,侏罗系烃源岩在大部分地区未成熟—低成熟,只在南部与东部坳陷达到成熟—高成熟,白垩系和古近系烃源岩目前也只在南部坳陷处于低成熟—成熟演化阶段。准噶尔盆地目前发现了6大类典型原油,其地球化学特征存在很大差异。第一类原油碳同位素组成特别重(δ~(13)C-26‰);第二类原油碳同位素组成轻(δ~(13)C-29‰)、含有丰富的胡萝卜烷、类异戊二烯烷烃、三环萜烷和伽马蜡烷,甾烷以C_(28)、C_(29)为主,基本没有重排甾烷;第三类原油碳同位素轻(δ~(13)C-29‰)、重排甾烷、Ts、C_(29)Ts及C_(30)重排藿烷异常丰富;第四类原油碳同位素组成重(δ~(13)C-28‰~-26‰),Pr/Ph大于2.5,三环萜烷含量低且以C_(19)、C_(20)为主,藿烷系列丰富,伽马蜡烷极低,甾烷以C_(29)规则甾烷及重排甾烷为主;第五类原油碳同位素组成轻(δ~(13)C-29‰)、Pr/Ph1.0、伽马蜡烷丰富且有两个异构体、Ts、C_(29)Ts、C_(30)重排藿烷、C_(27)~C_(29)异胆甾烷及C_(30)甲基甾烷十分丰富;第六类原油主要为中低成熟油,碳同位素组成重(δ~(13)C-28‰~-26‰),C_(27)、C_(28)、C_(29)甾烷呈Ⅴ型分布,甲藻甾烷异常丰富。第二类原油广泛分布于盆地不同区域,其他类型原油均只分布于盆地局部地区。西北缘地区以第二类原油为主,可分为3个亚类;腹部地区以第二类原油为主,可分为4个亚类,还有少量第四类原油;东部地区有前4类典型原油,此外还有混合原油;南缘地区目前发现有第二、第四、第五及第六类4种典型原油,也有少量混合原油。     

准噶尔盆地油气源、油气分布与油气系统

准噶尔盆地是中国西部典型的多旋回叠合盆地,发育有石炭系、二叠系、三叠系、侏罗系、白垩系和古近系6套烃源岩,同时存在6大类原油和3大类天然气,广泛分布于盆地不同地区。西北缘原油总体相似,碳同位素组成轻(δ~(13)C-29‰),胡萝卜烷、类异戊二烯烷烃、三环萜烷、伽马蜡烷丰富,甾烷以C_(28)、C_(29)为主,基本没有重排甾烷,为第二类原油,来源于二叠系湖相烃源岩。腹部绝大多数原油与西北缘原油相似,但胡萝卜烷、类异戊二烯烷烃、伽马蜡烷等有差异,来源于不同凹陷的二叠系湖相烃源岩;少量原油碳同位素组成重(δ~(13)C-28‰~-26‰),Pr/Ph大于2.5,三环萜烷以C_(19)、C_(20)为主,藿烷丰富而伽马蜡烷极低,以C_(29)规则甾烷及重排甾烷为主,为第四类原油,来源于侏罗系煤系烃源岩。东部存在5种类型原油,第一类原油碳同位素组成特别重(δ~(13)C-26‰),来源于石炭系烃源岩;第二类原油与腹部地区绝大多数原油十分相似,来源于二叠系湖相烃源岩;第三类原油碳同位索组成轻,重排甾烷、Ts、C_(29)Ts及C_(30)重排藿烷异常丰富,来源于中上三叠统湖相烃源岩;第四类原油源于侏罗系煤系烃源岩;混合类原油为二叠系、三叠系、侏罗系原油的混合,各自贡献平均分别为20%、15%和65%。南缘存在4类典型原油,为第二、第四、第五和第六类原油,其中第二、第四类分别源于二叠系和侏罗系;第五类原油碳同位素组成轻(δ~(13)C-29‰)、Pr/Ph1.0、伽马蜡烷丰富且有两个异构体、Ts、C_(29)Ts、C_(30)重排藿烷、C_(27)~C_(29)异胆甾烷及C_(30)甲基甾烷丰富,来源于白垩系湖相烃源岩;第六类原油主要为中低成熟原油,碳同位素组成δ~(13)C~28‰~-26‰,C_(27)、C_(28)、C_(29)甾烷呈"V"型分布,甲藻甾烷异常丰富,来源于古近系湖相烃源岩。准噶尔盆地天然气有油型气、混合气和煤型气,前两类主要来源于二叠系湖相烃源岩和石炭系海相烃源岩,煤型气主要来源于石炭系和侏罗系煤系烃源岩。不同类型油气分布与不同时代烃源灶具有良好对应关系:石炭系油气主要分布于陆东-五彩湾;二叠系油气主要分布于西北缘、腹部与东部;三叠系原油仅分布于东部;侏罗系原油主要分布于东部与南部;白垩系原油仅分布于南缘中部;古近系原油仅分布于南缘西部。按照盆地构造特征及不同时代烃源灶与油气关系,将准噶尔盆地划分为西部、中部、东部、南部及乌伦古5个油气系统及15个子油气系统。     

二连盆地稠油地球化学及其成因探讨

稠油在二连盆地内广泛分布,其成因可分为原生稠油和次生稠油两类。原生稠油来自未成熟或低成熟的白垩系烃源岩的直接排烃和原油运移过程中的分异,主要为普通稠油(粘度为100～5000mPa·s),而次生稠油则是原生稠油受生物降解、水洗和氧化等次生稠变的产物,并具有不同的稠化程度。基于大量稠油物性、饱和烃色谱和色质分析数据,探讨了不同类型稠油的特征,并根据稠化程度的差异将二连盆地稠油归纳为一个稠变序列,即低成熟—未成熟稠油(粘度100～2000 mPa·s)、轻度生物降解稠油(粘度500～5000 mPa·s)、中度生物降解稠油(粘度1000～50000 mPa·s)、重度生物降解稠油(粘度>50000 mPa·s)。随原油稠化程度的不断增加,其产物从普通稠油变化为特稠油。原油在盆地斜坡带和凹中隆起的高部位最容易发生次生稠变而形成稠油。多种稠变作用的叠加是二连地区稠油大面积分布的主要原因。     

鄂尔多斯盆地南部中生界原油地球化学特征及油源分析

系统采集鄂尔多斯盆地南部中生界的烃源岩、原油及油砂样品,对其饱和烃和芳烃馏分进行气相色谱-质谱分析,通过 对生物标志物组成特征的研究,分析和探讨中生界原油的油源。结果表明:根据 8β(H)-补身烷和 C3017α(H)-重排藿烷含量, 鄂尔多斯盆地南部中生界原油可划分为I,II,III类。第I类原油 8β(H)-补身烷含量高, C3017α(H)-重排藿烷含量低,来自 深湖相沉积相带的长 7 油页岩 (A1 类),第II类原油 8β(H)-补身烷含量较高, C3017α(H)-重排藿烷含量中等,来自深湖—半深 湖沉积相带的长 7 暗色泥岩 (A2 类),第III类原油 8β(H)-补身烷含量低, C3017α(H)-重排藿烷含量高,来自半深湖沉积相带的 长 7 暗色泥岩 (A3 类),由于采集样品数量限制,第III类原油不排除来自长 8 或长 9 暗色泥岩 (A3 类) 的可能,目前发现的原油 主要是第I类,即各油层组的原油主要是由长 7 油页岩提供的,它是鄂多斯盆地南部中生界的主力烃源岩。     

乌兰花凹陷原油特征及成因

乌兰花凹陷是二连盆地南部新发现的富油凹陷,对乌兰花凹陷原油物理性质和地球化学性质进行了系统的分析以揭示其特征及来源。原油物理性质显示,乌兰花凹陷原油比重（API gravity）介于20.2°~40.0°之间,主体为正常原油。原油生物标志化合物参数表明,不同构造带之间原油特征存在差异,可以划分为两类原油。一类以土牧尔构造带原油为主,具有低姥值比（Pr/Ph）和C₂₁/C₂₃三环萜烷,相对较高的伽马蜡烷/C₃₁藿烷和规则甾烷/C₃₀藿烷的特征,原油主要为烃源岩在成熟阶段早期的产物,主要以藻类来源为主。另一类原油包括赛乌苏和红井构造带原油,具有高姥值比（Pr/Ph）和C₂₁/C₂₃三环萜烷,相对较低的伽马蜡烷/C₃₁藿烷和规则甾烷/C₃₀藿烷,主要为陆源有机质和藻类有机质混合来源,原油具有更高的成熟度。原油碳同位素和正构烷烃单体烃碳同位素表明这两类原油应是一套烃源岩在不同成熟阶段的产物,原油主要来源于南洼槽阿尔善组烃源岩。阿尔善组烃源岩的非均质性和成熟度导致了两类原油的差异。      

酒泉盆地青西凹陷油气地质特征及下步勘探方向

酒泉盆地油气勘探始于20世纪20年代,先后发现了老君庙、鸭儿峡、单北、白杨河等油田。盆地在中、新生代经历了早白垩世断陷盆地演化阶段和新生代前陆盆地演化阶段,为断拗叠置型盆地。断陷期的酒泉盆地下白垩统赤金堡组和下沟组为一套纹层状泥质白云岩和白云质泥岩,藻纹层比较发育,是优质的烃源岩。拗陷期盆地的快速沉降导致烃源岩快速成熟、高效生烃,为油气运移提供了动力,同时挤压逆冲对构造圈闭、油气运移通道的形成和储层物性的改善起着关键的作用,形成的窟窿山等多个正向构造带是油气富集的有利区带。青西凹陷存在低成熟、成熟、高成熟3类原油,低成熟原油仅分布于青西凹陷的下沟组上段至中沟组,成熟原油发生了大规模的运移,形成了柳沟庄、鸭儿峡—老君庙—石油沟油田,而深层高成熟原油没有大规模向中浅层运移,青西凹陷具有寻找高成熟原油的资源潜力。希望该研究成果可为青西凹陷下白垩统油气勘探提供经验与思路。     

On the depth,time and mechanism of origin of the heavy to medium-gravity naphthenic crude oils

Paraffinic crude oils are designated ‘primary’ because their composition is very close or identical to that of the hydrocarbons extracted from the corresponding oil source rocks. Heavy and medium-gravity naphthenic crude oils, on the other hand, typically are quite different compositionally from hydrocarbon mixtures in either mature or immature shales.The normal paraffin carbon number odd/even ratio 2C₂₉/(C₂₈ + C₃₀) of all the heavy to medium-gravity crude oils which could be analysed are in exactly the same range as is observed for the primary paraffinic crude oils, namely 0.95–1.42. The naphthene indices of the medium to heavy gravity naphthenic crude oils and of the primary paraffinic crude oils from the same area are identical or close. These facts are significant because both the n-paraffin carbon number odd/even ratio and the naphthene index of shale hydrocarbons are strongly depth and subsurface temperature dependent. The facts observed demonstrate beyond question that, in the same area, the paraffinic precursors of the heavy to medium-gravity naphthenic crude oils are generated and expelled in the identical depth range, and from the same mature relatively deep oil source beds as the primary paraffinic crude oils. Later, during and/or after a generally upward migration into oil reservoirs, the primary crude may be transformed compositionally into a naphthenic crude oil.In none of the five widely scattered oil basins studied are medium to heavy naphthenic crude oils found at temperatures greater than a limiting subsurface temperature. The abruptness of the temperature cutoff of the change in oil compositions in all five oil basins, as well as the average value of the cutoff temperature of 66°C (150°F), leaves no doubt that the mechanism of this crude oil transformation process is microbial.Optical activity, which was observed in narrow saturate hydrocarbon fractions of the 80–325°C range of all microbially transformed crude oils, but not in the primary untransformed oils, is strong additional evidence for the microbial nature of the crude oil transformation process. The observed optical activity is explained by the microbial digestion at different rates of optical antipodes present in the primary paraffinic crude oils.To gain perspective the vast scale of the microbial oil transformation process in nature is pointed out. Billions of tons of heavy to medium-gravity naphthenic crude oils, originating from the microbial transformation of primary paraffinic oils, are present in oil fields and tar sands all over the world.     

混合原油的地球化学特征及成藏贡献率

含油气盆地中存在混合原油的现象非常普遍,按照形成条件可区分出4种不同的混合类型.地球化学研究表明不同有机相原油混合后体现各自母源的生物标志化合物组合特征;生物降解原油与正常原油混合后具有完整的饱和烃谱峰,同时还反映生物降解特点;不同成熟度的原油混合后既可检出热稳定性低的化合物,部分成熟度参数还可指示成熟特征;高成熟天然气与原油混合后,往往会使不同组分段的成熟度产生明显变化.特殊化合物绝对浓度定量法、生物标志化合物参数法、碳同位素法和拟合图版法是常见的定量成藏贡献率方法.针对混合原油地球化学识别和贡献率定量中的局限性,提出了利用指纹技术进行优化的思路.     

Petroleum potential of Baikal deposits

We analyzed oils, gases, and bitumens of bottom sediments from natural shows on the southeastern shore of Lake Baikal, in the mouth of the Stvolovaya River near Capes Tolstyi and Gorevoi Utes. Based on a set of geological data, we have established that: (1) the lake oils underwent biodegradation to a variable degree: “Fresh” nondegraded paraffin oil floats up near Cape Gorevoi Utes; in the mouth of the Stvolovaya River and near Cape Tolstyi, aromatic-naphthene oil lacks n-alkanes, monomethyl alkanes, and acyclic isoprenoids; (2) Cenozoic oil originated from the organic matter of fresh-water basins with significant amounts of higher land plant remains, including angiosperm plants (oleanane), which suggests the lake or delta genesis of oil source formations of Cretaceous and younger ages. Judging from the carbon isotope composition (average δ¹³C = −43.84‰), methane from the bottom sediments near Cape Gorevoi Utes is catagenetic. The initial in-place resources in the Baikal sedimentary basins are estimated by the volumetric-statistical method at 500 mln tons of equivalent hydrocarbons.     

柴达木盆地北缘侏罗系两类不同有机质丰度泥岩的 生物标志物特征对比研究

在柴达木盆地北缘地区,分别选取有机碳含量很低和较高的侏罗系泥岩样品,对比分析了它们在生物标志物组成上的差异。结果发现,高有机质丰度泥岩的生标组成与我国西北地区侏罗纪煤系有机质的特征差异不大,相比而言,低有机质丰度泥岩的正烷烃以前主峰为特征,Pr/Ph比值在1.0左右,三环萜烷和伽马蜡烷丰度较高,并在部分样品中检出了25 降藿烷系列。结合泥岩的有机岩石学特征,认为这些差异可能反映了泥岩沉积环境和生烃母质的不同:高有机质丰度泥岩的有机显微组分以相对弱还原条件下的形态有机质为主,包括藻类体、孢子体和角质体等,而低有机质丰度泥岩的有机显微组分以相对强还原条件下的矿物沥青基质为主,其母质可能来源于低等显微菌藻类。进一步通过对比不同有机质丰度泥岩,以及区内原油生标组成之间的相互关系,讨论了研究区的油源问题。     

Geological and geochemical studies of heavy oil reservoirs in China

Thickened heavy oils in China are genetically characteristic of continental fades. As to their physico-chemical properties, these oils are very high in viscosity and low in sulphur and trace element contents. In the group constituents, the concentrations of non-hydrocarbons and asphaltene are very high but those of saturated hydrocarbons and aromatics are very low. The gas chromatograms of alkanes show that these heavy oils have high abundances of iso - alkanes and cyclic hydrocarbons. In all the steroids and terpenoids, bicyclic sesquiterpenoids, tricyclic diterpenoids, re - arranged steranes and gammacerane are strongly biodegradation - resistent. The formation of heavy oil reservoirs is controlled mainly by late basin ascendance, biodegradation, flushing by meteoric water and oxidation in the oil - bearing formations. According to their formation mechanisms, heavy oil reservoirs can be classified as four categories: weathering and denudation, marginal oxidation, secondary migration and thickening of bottom water. Spatially, heavy thick oil reservoirs are distributed regularly: they usually show some paragenetic relationships with normal oil reservoirs. Heavy oil reservoirs often occur in structural highs or in overlying younger strata. Their burial depth is about 2000m. Horizontally, most of them are distributed on the margins of basins or depressions. Weng Weijin, Guo Jiaofeng and Li Huaqi also took part in this work.     

Geological and Geochemical Studies of Heavy Oil Reservoirs in China

Thickened heavy oils in China are genetically characteristic of continenta .As to their physico-chemical properties,these oils are very high in viscosity and low in sulphur and trace element con-tents.In the group constituents,the concentrations of non-hydrocarbons and asphaltene are very high but those of saturated hydrocarbons and aromatics are very low.The gas chromatograms of alkanes show that these heavy oils have high abundances of iso-alkanes and cyclic hydrocarbons.In all the steroids and terpenoids ,bicyclic sesquiterpenoids,tricyclic diterpenoids,re-arranged steranes and gammacerane are strongly bildegradation-resistent.The formation of heavy oil reservoirs is controlled mainly by late basin ascendance,biodegradation,flushing by meteoric water and oxidation in the oil-bearing formations.Ac-cording to their formation mechanisms,heavy oil reservoirs can be classified as four categories:weathering and denudation,marginal oxidation,secondary migration and thickening of bottom water .Spacially,heavy thick oil reservoirs are distributed regularly:they usually show some paragenetic relationships with normal oil reservoirs.Heavy oil reservoirs often occur in structural highs or in overlying younger strata.Their burial depth is about 200m.Horizontally,most of them are distributed on the margins of basins or depressions.     

Naphthene-aromatic hydrocarbons in oils of different genesis

Naphthene-benzenes, naphthene-naphthalenes, and naphthene-phenantrenes have been extracted with methanol from mono-, bi-, and triarene fractions of oils of different genetic types from the West Siberian, Timan–Pechora, North Caucasian, and Pannonian (Serbia) oil-and-gas-bearing basins. The hydrocarbon composition and molecular-mass distribution (MMD) of naphthene-arenes have been determined by mass spectrometry. Naphthene-benzene and naphthene-naphthalene molecules contain one to six naphthenic cycles, whereas naphthene-phenantrene molecules contain one to three naphthenic rings. The number of carbon atoms in the alkyl groups of naphthene-benzenes, naphthene-naphthalenes, and naphthene-phenantrenes reaches 38, 20, and 19, respectively. Distinctive features of group compositions and MMD of naphthene-arenes have been revealed in oils generated by different organic matter.     

Origin and alteration of oils and oil seeps from the Sinú-San Jacinto Basin, Colombia

Liquid hydrocarbons have been detected in the subsurface as well as in the surface in the Sinú-San Jacinto Basin (northwestern Colombia). The origin of the oils has not been conclusively established especially in the southern part of the basin. The most likely source rocks in the basin are the Ciénaga de Oro Fm. of the Oligocene-Early Miocene and the Cansona Fm. of the Upper Cretaceous. In this study, oil samples, seeps and source rock extracts were analyzed by GC and GC/MS, and δ¹³C was determined to identify the source facies. The sulphur content and gravity data were also considered.Two organic facies were identified: one constituted by terrestrial organic matter deposited in siliciclastic sediments in marginal marine to deltaic environments and the other made up of marine organic matter deposited in marine costal shelf to pelagic environments. The oils from the former organic facies have low sulphur contents, whereas the oils from the latter facies have high sulphur levels. Correlation of the oil seeps from the former facies with the Ciénaga de Oro Fm. has not been clearly established. The oil seeps from the latter facies correlate well with the extracts from the source rocks of the Cansona Fm., deposited along the fold belt of San Jacinto (east side). The oil seeps are affected by moderate to severe biodegradation, whereas the oil from the only oil producing well in the Sinú Basin (Floresanto-6 well) has not undergone biodegradation.     

渤海海域辽东南洼斜坡带旅大29油田原油 地球化学特征与油源对比

辽东凹陷南洼斜坡带旅大29油田在沙河街组二段获得了高产轻质原油和天然气,展现了良好的勘探潜力。为了进一 步明确其原油母质来源、沉积环境和烃源岩层位,对原油、油砂样品和围区烃源岩样品进行了系统的地球化学分析和油源 对比。研究结果表明,原油为低硫（0.0733%）、高蜡（20.77%） 的轻质成熟原油。原油样品饱和烃色谱完整,主峰碳为 C19,显示未遭受明显生物降解作用。油砂样品埋藏较浅,部分遭受生物降解等的影响,饱和烃色谱基线呈现明显的 “UCM”鼓包现象。原油和油砂样品具有低C19 三环萜烷/C23 三环萜烷（0.10~0.18）、低C24 四环萜烷/C26 三环萜烷（0.49~ 0.53）、低C27重排甾烷/C27甾烷（0.30~0.43）、中等伽马蜡烷指数（0.14~0.17） 和中等-高4-甲基甾烷参数（0.30~0.36）,且 具有相对较重的全油碳同位素值（-27.1‰）。原油母质形成于淡水-微咸水的湖泊沉积环境,母源有机质以藻类等低等水 生生物为主,陆源有机质输入较少。旅大29油田原油主要来源于辽中凹陷和辽东凹陷沙三段烃源岩,同时有少量辽中凹陷 沙四段烃源岩的贡献。研究区高蜡轻质原油的形成主要受控于烃源岩母质来源,藻类等低等水生生物是高蜡轻质原油形成 的重要母质。