辽河盆地西部凹陷稠油成因类型及其油源分析

根据原油的成熟度、生物降解程度及生物降解后油气的注入情况等多元因素,将辽河盆地西部凹陷的稠油划分为原生稠油、降解型稠油和降解—混合型稠油,在此基础上对该区稠油的油源进行了分析;研究表明,富伽马蜡烷的未熟原生稠油和未熟—降解型及低熟—降解型稠油可能主要来源于沙四段源岩,富4-甲基甾烷型的原油可能与沙三段具有亲缘关系。     

八面河地区"未熟-低熟油"成因探讨

采用先进的多馏分绝对定量、非烃技术,配合有机地球化学常规分析,在地质、地球化学综合研究的基础上,主要从分子地球化学角度对东营凹陷八面河"未熟-低熟油"成因进行了剖析。成熟度、单体烃绝对定量、多馏分与多参数综合对比揭示,以往研究确认的埋藏较浅的有机质富集层段-沙四段未熟-低熟页岩段并非该区"未熟-低熟油"的主力烃源岩,该区原油主要来自已进入生油门窗的成熟烃源岩,未熟-低熟烃源岩供应的油气量非常有限。八面河"未熟-低熟油"并非真正意义上的未熟-低熟油,该区原油成因机理仍然遵循干酪根晚期降解成烃理论     

未熟—低熟油研究现状与存在的问题

目前存在多种未熟-低熟油成烃机理的说法，但现有未熟-低熟油生烃模式能否用于指导勘探仍然有待于进一步检验。富类脂可溶有机质生烃被认为是未熟-低熟油生烃模式之一，但依据舀烷(特别是甲藻舀烷)的分布特征，东营凹陷牛庄洼陷南斜坡沙四段富藻类未熟-低熟页岩与八面河油田的原油几乎没有可比性，充分说明低演化阶段的藻类类脂物并非该区原油的主要成烃母质。未熟-低熟油田总与邻近的有利生油凹陷相伴以及某些未熟-低熟油的混合成熟度性质，暗示未熟-低熟油区的成熟油贡献，该结论已为中国两个典型未熟-低熟油田即东营凹陷八面河油田与苏北盆地金湖凹陷的最近研究结果所证实。现有资源量计算方法不太适用于未熟-低熟油，这可能导致了部分油田未熟-低熟资源量计算结果偏高。生物标志物标样定量技术是识别原油未熟-低熟性及油源追踪的有效途径，在油气勘探过程中还应加强地化与地质的有机结合。     

山东东营凹陷八面河油田稠油成因分析

东营凹陷八面河地区原油物性呈规律性的变化,偏离生油中心的构造高部位主要分布稠油,靠近生油中心的构造低部位主要分布正常油。对原油族组成与化学成分的分析表明,八面河油田稠油具有低饱芳比、饱和烃含量低、链烷烃与低分子量萘、菲等轻质馏分严重缺失等轻度-中等降解油特征,邻区草桥油田稠油含较为完整的生物降解标志物--25-降藿烷系列,系严重降解油,反映该区稠油的形成与次生变化有关。同区具有相同或相似油气成因的沙子岭原油的成熟度（C₂₉甾烷ααα20S/(S+R)值为0.24~0.25）低于八面河的（C₂₉甾烷ααα20S/(S+R)值为0.31~0.44）,为典型未熟-低熟油。沙子岭的轻度或未降解油同样表现为正常油,反映八面河地区低温成烃与稠油无必然的联系,进一步验证八面河稠油主系次生成因。处于构造高部位的油藏由于埋深浅、保存条件差,导致水洗、生物降解等次生变化相对较强,最终形成稠油。     

泌阳凹陷核桃园组未熟——低熟油地球化学特征及精细油源对比

未熟-低熟油在南襄盆地泌阳凹陷广泛分布,并具有饱和烃含量较低、胶质和沥青质含量较高的特征.在分析泌阳凹陷未熟-低熟油地球化学特征的基础上,开展了精细油源对比,并研究了未熟-低熟油的形成条件.泌阳凹陷未熟-低熟油成熟度参数:C29ααα20S/(S R)峰面积比值为0.10～0.33,C29ββ/(αα ββ)峰面积比值为0.11～0.28,Ts/(Ts Tm)峰面积比值均不大干0.34,具有未熟一低熟油成熟度低的特征.利用伽马蜡烷/C30藿烷峰面积比值和三环萜烷/(C29 C30)藿烷峰面积比值两项指标将泌阳凹陷未熟-低熟油划分为A、B和C型.A型具有伽马蜡烷/C30藿烷峰面积比值和三环萜烷/(C29 C30)藿烷峰面积比值都较低的"两低"特征,母源主要为核三段上部泥质烃源岩;B型具有伽马蜡烷/C30霍垸峰面积比值和三环萜烷/(C29 C30)藿烷峰面积比值均较高的"两高"特征,与核三段下部泥质烃源岩具有很好的亲缘关系;C型具有伽马蜡烷/C30藿烷峰面积比值高,但三环萜烷/(C29 C30)藿烷峰面积比值低的"一高一低"特征,源岩为核二段白云岩.研究表明泌阳凹陷核三段和核二段未熟-低熟烃源岩高可溶有机质含量和有利的生储组合关系是研究区未熟-低熟油形成的两个重要条件.     

白音查干凹陷达尔其油田原油地球化学与物性特征

达尔其油田原油的粘度差异很大，稀油、普通稠油和特稠油均有分布。大部分稠油和特稠油正构烷烃分布完整，末见生物降解等次生变化的迹象，具有原生稠油的特征。通过对几个代表性原油和烃源岩的族组成、饱和烃GC和GC／MS分析可知，Da201和Dal402类型成熟稀油来源于埋藏较深、热演化程度较高的下白垩统腾格尔组和阿尔善组烃源岩，而Dal201类型末熟、特稠油则来源于埋藏浅、热演化程度低的下白垩统都红木组一段烃源岩。由油样Da201和Dal201混合(质量比68．7：31．3)而成的油样Da2 12，其族组成、饱和烃色谱和甾、萜烷分布特征与Dal401类原油接近。详细对比二者之间的差异，结果表明Dal401类原油比混合油Da2 12含有更多的成熟稀油．稀油比例大于68.7％。Dal401油层油砂样连续抽提实验结果表明，早期注入该油层的原油为Da201和Dal402类成熟稀油。晚期注入的原油为Dal201类末熟特稠油，这进一步证实了Dal401类油为混源油。     

舞阳、襄城盐湖盆地未熟-低熟油成藏模式

舞阳、襄城凹陷下第三生活费为膏、盐岩相盐湖沉积。半咸水-咸水湖相、盐湖相是形成未熟-低熟油的良好环境，沉积旋回中期断坳式沉积形成了主要油源层系，其高丰度未熟烃类推岩体是形成未熟-低熟油藏的物质基础，中-高孔、中-高渗碎屑岩层构成了未熟-低熟油藏的重要储集层，并发育了较好的生储盖组合，这些有利条件为舞阳、襄城凹陷形成未熟-低熟油藏提供了重要保证。指出凹陷陡坡带为背斜、断鼻型油藏分布区，还可能有混合型油藏；中部洼陷带为岩性油藏、裂隙型油藏发育区；斜坡带主要发育断鼻型油藏。     

未熟-低熟油生成机理的化学动力学研究及其初步应用

对树脂体、木栓质体、可溶有机质、富硫有机质、经细菌强烈改造过的有机质等各类与未熟─低熟油产出密切相关的样品及部分参照样品所进行的系统的化学动力学定量研究显示,虽然未熟─低熟油的产出和富集可能与多种不同的地质条件或因素有关,但它们的共同之处在于这些有机质较常规有机质具有明显偏低的成烃活化能。化学动力学模型的初步应用显示,这些有机质的确能在浅于常规生烃门限的地质条件下开始大量成烃,从而定量阐明了业已报道的各种地质条件下未熟─低熟油产出和富集的机理.     

未熟—低熟油的有机质成烃化学动力学模型

<正> 国内外大量的研究和勘探实践表明,虽然未熟—低熟油广泛存在,但并非所有的沉积盆地或层位均有未熟—低熟油产出并成藏。它们的产出和富集是与特定的地质条件相联系的,包括如下几个方面。(1)与特殊类型的有机质有关,如木栓质体、树脂体、某些藻类;(2)与强烈的细菌活动和改造有关;(3)与强还原环境有关;(4)与可溶有机质有关,黄第藩等则特别突出地强调了这种沉积可溶有机质作为未熟—低熟油气生成的主要母源的意义。有机质成油(包括未熟—低熟油)的过程是一个有机质     

南襄盆地泌阳凹陷油、碱共生的地质条件

南(阳)襄(樊)盆地泌阳凹陷是一个油、碱共生的蒸发岩盆地,已探明规模石油与天然碱(NaHCO3和Na2CO3·3NaHCO3)地质储量。原油分为成熟油和未熟(低熟)油,成熟油储集于碎屑岩中,未熟(低熟)油储集于白云岩的裂缝和孔洞之中,而天然碱矿的围岩就是白云岩(裂缝和孔洞中也有天然碱赋存)。其地质特征与美国绿河盆地和犹英塔盆地十分相似,油碱共生受控于大地构造背景、古地貌、古地理、古气候、古沉积环境和物质来源等地质条件。     

The evolution characteristics and fractionation mechanism of carbon isotopes in the process of "multi-stage hydrocarbon generation"

The Jiyang Sag and the Liaohe Basin are the two important areas where immature oil resources are distributed in China. From these two areas immature-low mature to mature oil samples were collected for carbon isotopic analysis. The extracts of source rocks are dominant in the Jiyang Sag while crude oils are dominant in the Liaohe Basin. The maturity index, R., for source rocks varies from 0.25%(immature) to 0.65% (mature). Studies have shown that within this range of R. values the extracts of source rocks and crude oils, as well as their fraction components, have experienced observable carbon isotope fractionation. The carbon isotopic values tend to increase with burial depth, the oils become from immature-low mature to mature, and the rules of evolution of oils show a three-stage evolution pattern, i. e. ,light→heavy→light→heavy oils. Such variation trend seems to be related to the occurrence of two hydrocarbon-generating processes and the main hydrocarbon-forming materials being correspondingly non-hydrocarbons and possessing MAB characteristics, lower thermodynamic effects and other factors. In the process towards the mature stage, with increasing thermodynamic effects, the thermal degradation of kerogens into oil has become the leading factor, and correspondingly the bond-breaking ratio of 12 C-13C also increases,making the relatively 12C-rich materials at the low mature stage evolve again towards 13C enrichment.     

C24–C27 Degraded triterpanes in Nigerian petroleum: novel molecular markers of source/input or organic maturation?

The analyses, by gas chromatography and gas chromatography/mass spectrometry, of the triterpane concentrate of crude oils sampled from various oil fields of the Tertiary Niger delta have revealed the ubiquitous presence of a series of C₂₄–C₂₇ tetracyclic alkanes likely to be novel degraded triterpanes. The presence in the crude oils of a C₂₅ tricyclic alkane, apparently structurally related to the tetracyclanes, seemed consistent with the hypothesis of sequential cleavages of the terminal rings of precursor pentacyclic triterpenoid derivatives with increasing thermal transformation of the respective petroleums.The degraded triterpanes might be useful for assessing the stages of thermal evolution of petroleum in the reservoir. A possible application, to oil exploration, of the expected variations in the concentration of the polycyclanes in crude oils with different thermal histories would be in distinguishing primary (immature) oils from mature but biodegraded oils.     

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.     

低成熟石油烃源岩的动力学研究

本文介绍了对东营凹陷下第三系沙河街组沙四段上部具有不同自然熟化程度的低成熟石油烃源岩进行动力学研究的结果。结果表明，浅埋藏、低成熟、低有机丰度且与碳酸盐岩相关的源岩具相对较高的烃产率和平均活化能；平均活化能可能会掩盖低熟成烃特征。依据研究结果，指出当前进入门限埋深以下且具有低活化能生烃母质存在的牛１１样品可能在浅埋藏、低成熟时曾为该区（八面河低熟油田）低成熟石油的形成提供了油源。另外，笔者通过对样品可溶有机质抽提前后活化能分布对比研究，指出了低活化能分布范围内的生烃母质主要为可溶有机质。并且进而提出本区低成熟石油的成油下限埋深划分至２８００ｍ为宜，其对应的下限反应活化能不超过１７７ＫＪ/ｍｏｌ。     

控制内蒙古二连盆地达尔其油田石油富集度的关键因素——不同油源原油的混合作用

在对3套烃源岩的质量和成熟度描述基础上,通过对原油物理性质、族组成和生物标志化合物参数的研究,在达尔其油田内划分出成熟度有明显差异的低熟油和成熟油。油源对比结果认为它们分别由都红木组一段低熟烃源岩和阿尔善组二段成熟烃源岩所生。推测成熟度参数介于低熟和成熟之间的原油为混源油。通过原油混合试验和油砂连续抽提试验证实了混源油的推测。通过油藏剖面中不同性质油层的分布特征研究,结合断层发育史与油气运移关系分析认为不同油源原油的混合是控制该油田石油富集度较高的关键因素。此外,还分析了控制混源的断层组合特征。     

Dinosterane and other steroidal hydrocarbons of dinoflagellate origin in sediments and petroleum

The steroidal alkanes of a selection of sediments and oils have been examined by GC-MS with multiple metastable reaction monitoring. Specific 4-methyl sterane isomers have been identified by comparison with isomers synthesized from sterols isolated from dinoflagellates. An immature marine oil shale and two mature marine oils of Triassic to early Cretaceous age contained high concentrations of C₃₀ steranes comprising desmethyl, 24-ethyl-4α-methylcholestane and 4α,23,24-trimethylcholestane (dinosterane) isomers. An immature non-marine oil shale and two non-marine oils of Cretaceous to Eocene age contained stereoisomers of 24-ethyl-4α-methylcholestane as the dominant C₃₀ steranes. Reaction monitoring analyses in GC-MS are particularly suited to unravelling complex distributions of homologous and stereoisomeric steroids encountered in oils and their source rocks.