塔里木轮南地区原油沥青质的分子结构及其初步应用:热解、甲基化-热解和RICO研究

利用瞬间热解、甲基化-热解和钌离子催化氧化(RICO)降解技术研究了塔里木盆地轮南地区原油沥青质的分子结构,并对其在石油地球化学研究中的指示意义进行了讨论.轮南地区原油沥青质分子中的取代官能团以烷基侧链为主,烷基桥次之,另外还有少量的烷基-环己烷、支链烷烃和苯系物,这些化合物可能大都以C-C键结合到缩合芳环体系上;沥青质分子中的芳环体系大多数可能是萘或菲类型的芳香结构,高度缩合的芳香结构可能较少.轮南地区不同构造带原油沥青质热解产物的一致性指示它们可能来自沉积环境相同的母源.沥青质的分子结构表明,其母源可能主要来自浮游藻类的类脂物.热解产物中较高含量的1,2,3,4-四甲基-苯和2,6-二甲基、2,6,10-三甲基烷烃类化合物的检出表明其母质可能形成于较强的还原环境.沥青质热解产物中姥鲛-1-烯的相对含量较低,RICO产物中一元脂肪酸远高于二元脂肪酸,指示该区原油具有较高的成熟度.部分脂肪酸类化合物通过酯键连接在沥青质分子中,可能反映了原油在储层中经历了生物降解等后生作用.     

鄂尔多斯盆地南部长7暗色泥岩与黑色页岩生烃动力学特征对比分析

以往对鄂尔多斯盆地南部地区长7油层组(简称长7)中烃源岩生烃潜力的研究主要是采用静态地球化学指标进行的,目前尚无对生烃动态特征的系统评价,因而制约了对长7烃源岩生烃潜力和页岩油资源分布有利岩性的客观认识。为此,选取长7不同类型的烃源岩样品,通过开放和封闭热模拟实验,对比分析了不同类型烃源岩的动力学参数、生烃产物、产率特征及生烃演化规律。结果表明:(1)黑色页岩活化能分布范围比暗色泥岩更为集中,且主频活化能和频率因子均低于暗色泥岩,体现了快速生烃的特性;(2)在外推到地质条件下,黑色页岩主要生烃期对应的R_o值(0.70%~0.87%)低于暗色泥岩(1.06%~1.72%),且以生油为主;(3)R_o在0.9%~1.3%范围内,黑色页岩的总烃产率高于暗色泥岩,生油量高于暗色泥岩。结合研究区两类烃源岩的地球化学资料综合分析表明,黑色页岩是研究区页岩油资源形成与分布的有利烃源岩。     

泥灰岩的生、排烃模拟实验研究

本文采用加水热模拟实验方法对东濮凹陷卫城地区下第三系低熟泥灰岩进行了生、排烃模拟实验研究，重点分析了液态产物（热解油、沥青Ａ、沥青Ｃ）的特征及演化规律。热解油中轻质烃（Ｃ₆－Ｃ₁₄）占有重要的地位，其相对含量随演化程度的增高变化特征是从大到小然后再增大，轻质烃的准确定量为评价泥灰岩的生油量提供了重要参数；热解油、沥青Ａ、沥表Ｃ三者的产率及组成变化的对比研究反映了泥灰岩（碳酸盐岩）中不同赋存状态有机质对成烃的贡献以及排烃机制。     

Chemical characterization of Lower Devonian vascular plants

Vegetative remains of three coalified Lower Devonian vascular plants (Zosterophyllum, Psilophyton, Renalia) were analyzed using flash pyrolysis-gas chromatography-mass spectrometry. The distributions of pyrolysis products are compared with those from younger vascular plant fossil xylem (Cordaixylon, Callixylon) and cuticle (Pachypteris). The likelihood of the chemical preservation of characteristic higher plant macromolecules (e.g., lignin and cutan) in the Lower Devonian plant fossils is considered in light of this comparison and associated thermal maturity assessments. Reflectance values from vitrinite-like macerals, which may not be vitrinite sensu stricto in the Lower Devonian host rocks for the fossils selected for this study, are shown to provide a reasonable assessment of the thermal maturity of these early vascular plant fossils. Although lignin altered through burial maturation is the most likely source of the prominent alkylphenols and aromatic hydrocarbons in the Lower Devonian tracheophyte flash pyrolysates, a contribution from thermally modified tannins cannot be ruled out. Comparison of the highly aliphatic pyrolysates from the Zosterophyllum and Psilophyton axes with that of a thermally mature fossil gymnosperm leaf revealed that cutan was an important component in the Devonian plant remains. This is the earliest chemical evidence for the presence of cutan in vascular plants.     

Similar morphological and chemical variations of Gloeocapsomorpha prisca in Ordovician sediments and cultured Botryococcus braunii as a response to changes in salinity

Most Ordovician source rocks consist of accumulation of a colonial marine microorganism, Gloeocapsomorpha prisca (G. prisca) whose nature, ecology and affinity with extant organisms have been in dispute for years. Furthermore, recent studies have shown major differences in phenol moieties between two G. prisca-rich samples. Examination of five G. prisca-rich kerogens by electron microscopy and pyrolysis studies revealed (i) the occurrence of two markedly distinct “morpho/chemical” types: a “closed/phenol-rich” type (Baltic samples) and an “open/phenol-poor” one (North American samples) and (ii) the selective preservation of the resistant micromolecular material building up the thick cell walls in the original organism. Comparison with extant Botryococcus braunii (a widespread green microalga) grown on media of increasing salinity suggests that G. prisca is likely to be a planktonic green microalga related to B. braunii, which can adapt to large salinity variations which, in turn, control its polymorphism. The large differences in colony morphology and in the content of phenol moieties observed in fossil G. prisca and the resulting occurrence of two “morpho/chemical” types, should therefore reflect depositional environments with different salinities. The presence of thick, highly aliphatic, resistant walls in G. prisca selectively preserved during fossilization, accounts for the major contribution of this organism to Ordovician organic-rich sediments and for the resulting typical signature of Ordovician oils.     

应用碳同位素动力学方法探讨阿克 1气藏天然气的来源

阿克 1气藏是塔西南前陆区喀什凹陷油气勘探上获得重大突破的工业性气藏.采用金管封闭体系热模拟实验和 GC-IRMS碳同位素测定,结合运用 GOR-ISOTOPE KINETICS专用软件,推导出了塔西南前陆区烃源岩 (煤和泥岩 )热解生成甲烷的碳同位素动力学参数.该区侏罗系煤、侏罗系泥岩和二叠系泥岩的平均活化能分别为 225.86 kJ/mol、 194.03 kJ/mol和 223.45 kJ/mol,甲烷 (12CH4)的指前因子各为 1.00× 1014 s-1、 1.00× 1013 s-1、 1.00× 1014 s-1.在此基础上,利用碳同位素动力学计算结果,并结合地质背景,进一步探讨了阿克 1气藏天然气的来源,为天然气定量评价提供了新思路.阿克 1气藏天然气为烃源岩过成熟阶段的烃产物,属于混源气,主要捕获了 Ro 为 2.0%～ 3.6%阶段的天然气;其气源区包括喀什凹陷中心和阿克 1井推覆体下盘,主力气源岩是石炭系烃源岩.     

Hydrous pyrolysis of New Albany and Phosphoria Shales: production kinetics of carboxylic acids and light hydrocarbons and interactions between the inorganic and organic chemical systems

Hydrous pyrolysis in flexible gold-bag autoclaves was used to study the production of carboxylic acids and light hydrocarbons from two marine type IIb source rocks (New Albany and Phosphoria Shales). Kerogen pyrolysis produced significant amounts of the monocarboxylic acids (acetic > propionic > butyric). The gases were dominated by CO₂ and methane, in that order, and progressively smaller amounts of the alkanes (ethane > propane > butane > pentane). Kinetic analyses of production rates for the New Albany Shale suggest mean activation energies (E) of 51-54 kcal/mol for both the light hydrocarbons and acids. Pressure had little effect on measured production rates for either shale over the pressure range investigated. Chemical thermodynamic speciation modeling suggests that in these experiments metal-organic acid anion complexation had little impact on aluminum speciation/solubility, but was important with respect to the alkaline earths.     

Resistant biomacromolecules in marine microalgae of the classes Eustigmatophyceae and Chlorophyceae: Geochemical implications

Non-hydrolysable macromolecular constituents (i.e. algaenans) were isolated from two out of seven marine microalgae investigated. Nannochloropsis salina and Nannochloropsis sp. from the class of Eustigmatophyceae produce highly aliphatic algaenans. Flash pyrolysis and chemical degradations with HI and RuO₄ allowed for the identification of their chemical structure, which is mainly composed of polyether-linked long-chain (up to C₃₆) n-alkyl units. The building blocks of this polymer were also recognized in lipid fractions. The green microalgae (Chlorophyceae) Chlorella spaerckii, Chlorococcum sp. and Nannochloris sp. were earlier thought to biosynthesize algaenans comprising aliphatic and/or aromatic moieties. However, a new isolation method utilizing trifluoroacetic acid (TFA) prior to the other hydrolyses revealed that the macromolecular material isolated from these three chlorophytes was either hydrolysable with TFA or artefacts from the former method. Similar to algaenans from fresh water green microalgae, the aliphatic eustigmatophyte algaenans are likely to be selectively preserved in depositional environments and might ultimately serve as source rock organic matter of marine crude oils. Furthermore, they may play an important role in the cycling of carbon.     

Geochemical significance of lipids and lipid-derived substructures interlaced in kerogen

Young kerogens isolated from seven freshwater lakes, six river mouths and four marine surface sediments were subjected to pyrolysis in vacuo. Their pyrolysates were trapped and separated subsequently for determination of hydrocarbons, fatty acids and alcohols. The abundances, carbon number distributions of long (C₁₂) polymethylene chain lipid compounds and relative abundances of pristenes are proposed as possible indices applicable to discrimination between young kerogens from freshwater lacustrine and marine sediments. Some oil-shale kerogens of Eocene and Permian age were pyrolyzed in the same way, where the chain-length distributions of the pyrolysis products showed similar trends as those observed for the pyrolysis of young kerogens.     

A comparison of organosulphur compounds produced by pyrolysis of asphaltenes and those present in related crude oils and tar sands

Asphaltenes and NSO fractions from a variety of oils and tar sands have been characterized by pyrolysis-gas chromatography (Py---GC) using both flame ionization and flame photometric detectors. Organosulphur compounds were not always produced by pyrolysis of the asphaltenes isolated from the biodegraded tar sand extracts although pyrolysis of the NSO fractions produced a series of thiophenes from all of the samples examined. These observations suggest that under certain conditions, asphaltene fractions may be affected by biodegradation, leading to preferential removal of the sulphur containing compounds. In addition, it was observed that Py---GC of asphaltenes permitted oils to be differentiated on the basis of their source rock lithology. Oils derived from carbonate source rocks produced thiophene/benzothiopene ratios <1 whilst the same ratio was >1 for oils derived from shales. Thiophene/dibenzothiophene ratios could be used in a similar manner.