成烃理论的发展——（Ⅱ）煤成油及其初次运移模式

近几年来，我国针对侏罗系煤系地层的油气勘探，取得了重大突破。在我国西北区的一些含煤盆地中都发现了丰富油气矿藏。煤成油的勘探开发和研究，是对陆相生油理论的重大发展，本文介绍了秦匡宗提出的一种利用＾１３Ｃ ＮＭＲ谱确定油潜力碳、气潜力碳和芳构碳评价生油气潜力的新方法，以及一种煤成烃的阶段性初次运移模式。     

吐哈盆地煤成油形成的地质条件

吐哈盆地是典型的煤成油气盆地。通过对该盆地煤成油形成的地质条件分析，认为煤成油藏的形成是特定地质条件下的产物。（１）盆地构造演化控制了煤系生储油岩系发育；（２０存在低成熟成烃母质以利于烃类排出：（３）成煤沼泽氧化还原环境与成煤植物差异造成了煤原始怪程度的不同。下三角洲平原沼泽及分流间湾沼泽是煤成烃发育的有利场所，流水沼泽相是煤成烃最有利的相带；（４）适合古地温梯度及后续盆地继承发展以保持源岩熟化，     

海拉尔盆地煤及煤系泥岩生排烃定量评价

海拉尔盆地具有多煤阶煤分布。煤系源岩生、排烃数据反映:最好的煤层是南上段,其次是大上段;最有利的煤系泥岩是铜钵庙组与南屯组。各凹陷煤系源岩生气量大小顺序为:呼和湖凹陷>贝尔凹陷>乌尔逊凹陷>呼伦湖凹陷。各凹陷煤系源岩生油量多少顺序为:乌尔逊凹陷>呼和湖凹陷>贝尔凹陷>呼伦湖凹陷。煤系源岩排油量大小顺序为:乌尔逊凹陷、贝尔凹陷、呼和湖凹陷、呼伦湖凹陷。可见,乌尔逊凹陷、贝尔凹陷、呼和湖凹陷具有良好的煤成油气勘探前景,是海拉尔盆地寻找煤成气、煤成油资源不可忽视的有利地区。      

中国侏罗系煤成油若干问题

在阐述了煤成油的概念，总结和评述了煤生油显微组分，生油门限，生油范围和生油高峰等问题后，本文通过吐哈等盆地侏罗系煤生油显微组分组成特征，可溶有机质演化，成熟度和有机质丰度，油源及原油成熟度对比；含煤岩系中煤层和泥岩的厚度及总量和煤及泥岩最高沥青和总烃转化率的对比； 其族组成和煤成原油的族组成特征的对比，提出了中国侏罗系煤成油盆地中泥岩比煤层对煤成油田形成有大的贡献看法。     

鄂尔多斯盆地延安组煤有机岩石学研究

鄂尔多斯盆地侏罗纪延安组煤系地层可否成为该盆地另一套油源岩的问题,历来存有争议。系统的煤岩和有机岩石学分析表明:煤中倾油性的壳质组分含量低,基质镜质体的类型也不利于生油,因此,延安组煤系有机质不大可能形成具有工业价值的煤成油藏     

“煤成油”—能源勘探的一个新领域

含煤地层中以腐殖型有机质为主的成煤物质在成煤过程中、特别是在沥青化过程中形成的“煤成油”已经成为能源勘探中的具有极大吸引力的一个重要方向。我国的油田多为陆相成因,属高含蜡质油,含油岩系与煤系共生或有密切关系。“煤成烃”理论,尤其是“煤成油”理论无论在理论上或实践中都存在许多需要解决的问题。“煤成油”理论所涉及的问题综其根本不外三个主要方面:一是煤及煤的各组成部分的成油能力和鉴定特征;二是形成物的运移,特别指的是初次运移;三是烃源对比和源源对比。而实用意义则在于对煤成油分布规律的研究和对开发的经济可行性的评价。     

煤系源岩倾油倾气性研究

利用固体13C核磁共振波谱检测源岩干酪根中油、气潜力碳的相对含量,并利用该参数直接判别各类源岩在"液态窗"阶段的倾油、倾气性.有些煤系源岩虽然其地球化学特征属腐植型母质,但由于其干酪根的脂碳中油潜力碳>气潜力碳,故仍以生油为主.该方法从生烃机理出发进一步揭示了新疆焉耆盆地中、下侏罗统煤系源岩以生油为主的根本原因.     

我国聚煤盆地煤系烃源岩生烃评价与成烃模式

本文应用有机岩石学方法与有机地球化学方法通过对我国煤成烃盆地典型煤系烃源岩的研究，担子同煤系烃源评价指标与标准，并以显微组分成煤规律为基础，建立起了我国含煤岩系的四种主要成烃模式。本研究成果对我国煤成烃勘探具有重要指导意义。     

生油的煤

煤是东南亚许多第三纪盆地的油源岩。这些富氢、贫氧煤的先质体是滨海平原泥炭,它们主要发育于长年潮湿的热带气候区。在这些环境中,水流再改造作用使脂质组干酵根相对于镜质组干酪根富集。本文将对库塔伊盆地的中新世煤系生油岩的分布、岩石学及化学特征加以描述,对第三纪及同期的滨海平原沉积的研究可应用于挪威海区油源者的分布,这里还将就挪威海区各盆地含煤岩系的沉积环境与其可能生油和(或)气潜力的关系进行评述。Haltenbanken地区三叠纪—侏罗纪煤越拿近三角洲边缘可能越易于生油,编制岩相图可能有助于该区的石油勘探。     

论富氢镜质组型腐殖煤—生油煤的一种新类型

根据大量样品综合配套分析研究结果，提出并论证了中国南华北盆地晚石炭世太原组（Ｃ＿２）富镜质组腐殖煤是一种新的煤型油源岩或生油煤。其特点是主要油源组分不是类脂组而是镜质组；确切地说，它是一种有少量类脂组“参与”的、主要由富氢镜质体构成的富镜质组腐殖型的生油煤。这种新型生油煤的发现和确定是“煤成烃”和“镜质组生油”领域的重要突破，具有全球性的科学与战略意义。     

临清坳陷东部煤成气藏的主控因素及成藏模式

临清坳陷是渤海湾盆地油气资源的重要勘探研究区,其煤成气藏潜力大,但研究程度较低。从多角度入手,通过解剖典型的煤成气探井,分析研究了临清坳陷东部煤成气藏的主控因素及成藏模式。研究结果显示:该区煤岩以Ⅲ型干酪根为主,暗色泥岩以Ⅱ₂-Ⅲ型干酪根为主,易于生气（油）;油气运移以近源输导为主;煤成气成藏主要受控于圈闭的赋存条件、油气输导、生储盖组合以及优质烃源岩分布等4个方面;成藏模式主要划分为源内成藏和源外成藏两种模式,其中源内成藏模式是今后该区勘探的主体,源外成藏的I型为进一步攻克对象。      

焉耆盆地侏罗纪煤系源岩显微组分组合与生油潜力

焉耆盆地为我国西部含煤、含油气盆地, 侏罗系含煤地层是最重要的潜在源岩.对侏罗纪煤系中的暗色泥岩、碳质泥岩和煤层分别进行了有机岩石学、Rock-Eval热解分析和核磁共振分析.泥岩、碳质泥岩和煤层具有不同的有机岩石学和有机地球化学特征, 其中煤层具有3种有机显微组分组合类型, 不同显微组分组合类型的煤层具有不同的生油、生气潜力或倾油、倾气性.基质镜质体、角质体、孢子体等显微组分是煤中的主要生烃组分.侏罗系泥岩、碳质泥岩和煤层具有不同的生物标志物分布特征, 生物标志物组合分析表明焉耆盆地已发现原油是泥岩、碳质泥岩和煤层生成原油的混合产物.含煤地层的地球化学生烃潜力分析和已发现原油的油源对比均表明, 含煤地层不仅是重要的气源岩, 而且可成为有效的油源岩.      

Hydrocarbon genesis of Jurassic coal measures in the Turpan Basin, China

A typical case of coal-derived oils in China, i.e. the crude oils from the Middle-Lower Jurassic coal measure strata in the Turpan Basin, is presented. By means of oil-source correlation, it is confirmed that low maturity crude oil in the Shengjinkou oil field is derived from the coal-bearing Qiketai Formation of Middle Jurassic age, a brackish lacustrine sediment. Mature crude oils in the Qiketai oil field, and in well Taican 1, are sourced from the Badaowan Formation of Lower Jurassic age, which contains coal seams as thick as 100 m. Results show that commercial accumulations of liquid crude oils can be generated from coals and coal measure strata containing high volatile coal of bituminous rank. Despite unfavourable types of source material, the total hydrocarbon-generating potential can be great due to the unusual abundance of organic matter.     

煤和煤系泥岩生油能力再评价

煤和分散有机质（煤系泥岩或页岩）对煤成油田的贡献大小一直没有获得统一认识,这导致煤是否具有生排油能力直到现在仍然争论不休。选择了两个典型侏罗系煤和一个煤系泥岩样品,分别进行了限定体系热解生烃模拟,结果表明热解特征较差的泥岩（H／C 0．77,IH 146mg／g）却比中等富氢煤（H／C 0．82,IH 260mg／g）的生油量高出2．7倍,是一般煤（H／C 0．75,IH 199mg／g）生油潜力的6倍。这暗示着在煤成油评价中,不能简单把煤和煤系分散有机质对等进行评价,不然会低估煤系相对分散有机质的贡献而过高估计了煤的作用。热解模拟结果与吐哈盆地台北凹陷煤系岩石中有机质含量对比结果表明,该凹陷煤成油更可能来自于煤系泥岩而不是煤本身。此外,通过分析发现煤中液态烃稳定性较差,一般在低熟阶段就开始裂解生气,因此,被国内外学者普遍采纳的,IH（或S1）随成熟度变化的趋势不能作为判断煤排油门限的有效参考。     

Oil-generating potential of Tertiary coals and other organic-rich sediments of the Nyalau Formation,onshore Sarawak

The oil-generating potential of coals and other organic-rich sediments from the Late Oligocene–Early Miocene Nyalau Formation, the offshore extension of which is believed to be a major source rock, is evaluated. Coals of the Nyalau Formation are typically dominated by vitrinite, with moderate and low amounts of exinite and inertinite, respectively. Significant amounts of clay minerals are present in these coals and those containing between 15 to 65% mineral matter by volume are termed carbargilite. The samples analysed range from sub-bituminous to high-volatile bituminous rank, possessing vitrinite reflectance in the range 0.42% to 0.72%. T_max values range from 425°–450°C which is in good agreement with vitrinite reflectance data. Good oil-generating potential is anticipated from these coals and carbargilites with moderate to rich exinite content (15–35%). This is supported by their high hydrogen indices of up to 400 mgHC/gTOC, Py–GC (S2) pyrograms with n-alkane/alkene doublets extending beyond nC₃₀, and their being in the early to mid-mature oil-window range. Petrographically, the most significant evidence of the oil-generating potential of these coals is the generation of petroleum-like materials (exsudatinite) visible under the microscope. Exsudatinite is a secondary maceral, commonly considered to represent the very beginning of oil generation in coal, which is shown here to also have an important role to play in hydrocarbon expulsion. The precursor of exsudatinite in these coals is the maceral bituminite which readily expels or mobilizes to hydrocarbon-like material in the form of oil smears and/or exsudatinite as observed under the microscope. The maceral bituminite is considered to play a major generative role via early exsudatinite generation, which is considered to facilitate the overall expulsion process in coaly source rocks.     

Coal as a source rock for oil: a review

The geological debate about whether, and to what extent, humic coals have sourced oil is likely to continue for some time, despite some important advances in our knowledge of the processes involved. It is clear that not only liptinites, but also perhydrous vitrinites have the potential to generate hydrocarbon liquids in the course of natural coalification. Some liptinites, especially alginite, cutinite, and suberinite, contain a higher proportion of aliphatic moieties in their structure than other liptinites such as sporinite and resinite and are, therefore, more oil-prone. It is of potential value to be able to predict the several environments of deposition in which coals with high liptinite contents or containing perhydrous vitrinites may have been formed. Review of the distribution of oil-prone coals in time and space reveals that most are Jurassic–Tertiary with key examples from Australia, New Zealand, and Indonesia. Methods based both on experimental simulations and the examination of naturally matured samples have been used to determine the order of generation of hydrocarbons from different macerals. Results are not entirely consistent among the different approaches, and there is much overlap in the ranges of degradation, but it seems probable that in the natural environment vitrinites begin to generate early, followed by labile liptinites such as suberinite, then cutinite, sporinite, and, finally, alginite.Petroleum potential may be determined by experimental simulation of natural coalification or inferred through various micro-techniques, especially fluorescence and infrared (IR) spectroscopy, or bulk techniques such as elemental analysis and ¹³C NMR spectroscopy. The latter three techniques enable a measure of the polymethylene component of the coal, which now appears to be one of the best available approaches for determining petroleum potential. No method of experimental simulation of petroleum generation from coals is without criticism, and comparative results are highly variable. However, hydrous pyrolysis, confined pyrolysis, and forms of open-system hydrous pyrolysis approach acceptable simulations.Whether, and to what degree generated liquid hydrocarbons are expelled, has long been the central problem in ‘oil from coal’ studies. The structure of vitrinite was believed until recently to contain an interconnected microporous network in which generated oil would be contained until an expulsion threshold was attained. Recent studies show the pores are not interconnected. Combined with a dynamic model of pore generation, it now seems that expulsion of hydrocarbons is best explained by activated diffusion of molecules to maceral boundaries and ultimately by cleats and fractures to coal seam boundaries. The main reason for poor expulsion is the adsorption of oil on the organic macromolecule, which may be overcome (1) if coals are thin and interbedded with clastic sediments, or (2) if the coals are very hydrogen-rich and generate large quantities of oil.The existence of oil in vitrinite is attested to by solvent extractions, fluorescence properties, and by microscopic observations of oil and bitumen. Experimental simulation of expulsion of oil from coals has only recently been attempted. The relative timing of release of generated CO₂ and CH₄ could have considerable importance in promoting the expulsion of liquid hydrocarbons but the mechanism is unclear. As it is universally agreed that dispersed organic matter (DOM) in some shales readily generates and expels petroleum, it is curious that few consistent geochemical differences have been found between coal macerals and DOM in interbedded shales.Unambiguous evidence of expulsion from coals is limited, and in particular only a few commercial oil discoveries can be confidently correlated to coals. These include Upper Cretaceous Fruitland Formation coals in the USA, from which oil is produced; New Zealand Tertiary coals; and Middle Jurassic coals from the Danish North Sea. It is likely that coals have at least contributed to significant oil discoveries in the Gippsland Basin, Australia; in the Turpan Basin, China; and in the Kutei and Ardjuna basins in Indonesia, but this remains unproven. Early reports that early Jurassic coals in mid-Norway were a major source of the reservoired oils have been shown to be inaccurate.None of the proposed ‘rules of thumb’ for generation or expulsion of petroleum from coals seem particularly robust. Decisions on whether a particular coal is likely to have been an active source for oil should consider all available geological and geochemical information. The assumptions made in computational models should be well understood as it is likely with new understandings of processes involved that some of these assumptions will be difficult to sustain.     

煤和含煤岩系成油理论研究和演变历史

运用系统的历史和现实类比分析方法,对世界含煤岩系煤成油田的源岩成熟度、烃源岩类型和煤成油田形成条件进行了综合研究。结果表明,煤虽能生油,但难以形成有商业意义的油田;含煤岩系中泥岩是煤成油田形成的主要贡献组分,在含煤盆地中,难以形成低熟煤成油田。      

造缝产烃还是改质造烃？——论含油气源岩层系的储集层属性和烃源岩属性

源岩层系油气已成为世界油气工业体系中举足轻重的重点领域，未来发展潜力很大。本文通过深入解读含油气源岩层系的地质形成条件，发现储集层属性和烃源岩属性在根本上决定了源岩层系油气成功开发的技术路径。储集层属性是指储集层储存和渗滤油气的物理性质及其相互关系，地史时期微—纳米级孔- 喉- 缝系统充注和聚集了大面积连续型油气资源，人工压裂形成缝网系统突破了致密储层的连通属性短板，成功开发了规模油气资源，突破流动属性短板可能是另一个发展方向。烃源岩属性是指烃源岩滞留、转化和排出油气的物理化学性质及其相互关系，包括已转化的滞留油气和未转化的残留有机质，滞留及潜在烃类资源规模巨大，地下人工加热等方式理论上可突破烃源岩的有机质数量和成熟度属性短板，可能是实现成功开发的有效路径。储集层属性和烃源岩属性是实现源岩层系油气规模发展的内在潜质基础，公共属性参数是外部环境基础。造缝产烃还是改质造烃？前提是准确研判优选何种内在属性参数，基础是系统整合优化所有外在属性参数，推动实现源岩层系油气商业化可持续发展，未来中低熟富有机质页岩及油页岩、中高熟富气态烃页岩层系、低变质程度富油煤岩、深层可气化煤炭等是值得期待的战略发展领域。