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.     

Observations on Indian Permian Gondwana Coals Under Fluorescence Microscopy: An Overview

Macerals like sporinite, cutinite, suberinite and resinite of the liptinite group have been insufficiently recorded in Indian Permian Gondwana coals, until the fluorescence microscopy came into existence. With the introduction of this technique, macerals like bituminite, fluorinite and exsudatinite were convincingly recognized and alginite and liptodetrinite, normally mistaken for mineral matter under normal reflected light in routine coal petrographic analysis, were identified with certainty. Thus, fluorescence microscopy has added certain new macerals to the tally of the liptinite group and has increased their overall proportion in Indian Gondwana coals.In addition to the liptinite group, collodetrinite (=desmocollinite) and a certain fraction of collotelinite (=telocollinite) macerals of the vitrinite group were found to be fluorescing with dull reddish-brown to dark brown colours. Certain semifusinite and inertodetrinite macerals of inertinite group were also found to fluoresce with almost identical intensity and colour as that of the associated perhydrous (fluorescing) vitrinite. Contributions of degraded resinite, algal matter and bitumen in the formation of perhydrous vitrinite have been established. The fluorescence behaviour of inertinite appears to be related with its genesis from partial oxidation of resin/bitumen-impregnated cell walls.     

湘中南龙潭煤系不同演化程度煤的煤岩学特征及有机地球化学特征

摘 要　 通过对湘中南龙潭煤系不同煤级煤样的煤岩学和有机地球化学研究‚概括了湘中南 龙潭煤系煤的有机显微组成和主要有机地球化学特征‚指出其中的气煤、肥煤和焦煤是具有 较高生烃潜力的烃源岩‚壳质组和基质镜质体是这一阶段煤中的主要生烃组分。     

栓皮栎的热模拟特征及木栓质的成烃演化

由于大多数沉积有机质或煤层中的木栓质体在很低演化阶段荧光就消失了，使得地球化学家和煤岩学家往往低估了木栓质体对成烃的贡献。利用显微镜荧光检测和显微傅里叶红外光谱技术对现代植物栓皮栎的树皮进行人工热模拟研究，结果表明现代木栓组织和木检质成分是一种高度偏油的有机质，在低热力条件下释放出大量的以异构烃和环烷烃为主的液态烃类，大约在镜质体反射率为０．５％之前，生成Ｃ６＋烃类总量的２／３以上。现代木栓热模拟生烃现象要滞后于地质体中的木栓质体，它不能完全复制木栓质体的自然熟化过程     

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.     

The geology, petrology, palynology and geochemistry of Permian coal basins in Tanzania: 2. Songwe-Kiwira Coalfield

This study provides coal quality, petrological, palynological and geochemical (Rock Eval) data on Permian coal seams and associated shales and mudstones of the Karoo Supergroup of the Songwe-Kiwira Coalfield, Tanzania. The coal seams, which have a cumulative thickness of 6.80 m, occur in the shale–coal–sandstone facies of the Mchuchuma Formation of Artinskian to Kungurian(?) age.Coal quality data (calorific values, volatile matter contents) and vitrinite reflectances indicate high volatile C bituminous to high volatile A bituminous coals, having relatively high ash yields (22–49 wt.%) and highly variable sulphur contents (0.17–9.2 wt.%). They could be used to fuel small-scale power generation units thereby providing electricity to nearby towns and villages. Also, the coals could be used as a substitute for wood, which is becoming increasingly scarce. In rural Tanzania, charcoal is still the main energy source for cooking, and wood is used extensively in brick kilns and for making roofing tiles.Petrological analysis indicated that the coals are dominated by dull to banded dull lithotypes, with seams at the base of the Mchuchuma Formation enriched in inertinite macerals (up to 83 vol.%), whereas up-section vitrinite contents increase. Palynological analyses indicated that the assemblage in the lower Mchuchuma Formation (Scheuringipollenites assemblage) is dominated by trilete spores, whereas in the remainder of the section, non-taeniate disaccates dominate (Scheuringipollenites–Protohaploxypinus assemblage). Facies critical macerals suggest for most seams a marsh/wet forest swamp depositional setting, which is consistent with the palynological data.Rock Eval analyses indicate type II/III kerogen, with Tmax (°C) values ranging from 426 to 440, corresponding to the early stage of hydrocarbon generation. Thermal Alteration Indices (2 to 2+) and vitrinite reflectance levels (0.60–0.83 Ro (%) support the Rock Eval maturity assessment, and despite the predominance of terrestrial-derived organic matter, there is evidence of oil generation and expulsion in the form of cavity and fracture filling exsudatinite.     

The petroleum generation potential and effective oil window of humic coals related to coal composition and age

A worldwide data set of more than 500 humic coals from the major coal-forming geological periods has been used to analyse the evolution in the remaining (Hydrogen Index, HI) and total (Quality Index, QI) generation potentials with increasing thermal maturity and the ‘effective oil window’ (‘oil expulsion window’). All samples describe HI and QI bands that are broad at low maturities and that gradually narrow with increasing maturity. The oil generation potential is completely exhausted at a vitrinite reflectance of 2.0–2.2%R_o or T_max of 500–510 °C. The initial large variation in the generation potential is related to the original depositional conditions, particularly the degree of marine influence and the formation of hydrogen-enriched vitrinite, as suggested by increased sulphur and hydrogen contents. During initial thermal maturation the HI increases to a maximum value, HI_max. Similarly, QI increases to a maximum value, QI_max. This increase in HI and QI is related to the formation of an additional generation potential in the coal structure. The decline in QI with further maturation is indicating onset of initial oil expulsion, which precedes efficient expulsion. Liquid petroleum generation from humic coals is thus a complex, three-phase process: (i) onset of petroleum generation, (ii) petroleum build-up in the coal, and (iii) initial oil expulsion followed by efficient oil expulsion (corresponding to the effective oil window). Efficient oil expulsion is indicated by a decline in the Bitumen Index (BI) when plotted against vitrinite reflectance or T_max. This means that in humic coals the vitrinite reflectance or T_max values at which onset of petroleum generation occurs cannot be used to establish the start of the effective oil window. The start of the effective oil window occurs within the vitrinite reflectance range 0.85–1.05%R_o or T_max range 440–455 °C and the oil window extends to 1.5–2.0%R_o or 470–510 °C. For general use, an effective oil window is proposed to occur from 0.85 to 1.7%R_o or from 440 to 490 °C. Specific ranges for HI_max and the effective oil window can be defined for Cenozoic, Jurassic, Permian, and Carboniferous coals. Cenozoic coals reach the highest HI_max values (220–370 mg HC/g TOC), and for the most oil-prone Cenozoic coals the effective oil window may possibly range from 0.65 to 2.0%R_o or 430 to 510 °C. In contrast, the most oil-prone Jurassic, Permian and Carboniferous coals reach the expulsion threshold at a vitrinite reflectance of 0.85–0.9%R_o or T_max of 440–445 °C.     

准噶尔盆地南缘侏罗系烃源岩排烃效率研究

准噶尔盆地南缘下部成藏组合勘探日趋重要,其主力烃源岩生烃潜力和排烃效率的研究亟待加强。根据排烃门限理论,利用生烃潜力法建立了准噶尔盆地南缘侏罗系烃源岩的生、排烃模式,并计算了烃源岩的生烃量、排烃量和排烃效率。研究表明,准噶尔盆地南缘侏罗系泥质烃源岩和煤层的排烃门限对应的镜质组反射率均为0. 7 %。侏罗系烃源岩的总生烃量为3 973. 84 x 108t,总排烃量为1 402. 71 x108t,其中八道湾组烃源岩排烃量占总排烃量的69.85%。准噶尔盆地南缘侏罗系烃源岩的平均排烃效率为35. 30%,不同层系不同岩性烃源岩,其排烃效率明显不同,泥质烃源岩排烃效率远大于煤层。综合分析认为,准噶尔盆地南缘侏罗系烃源岩生、排烃量大,排烃效率较高,下部成藏组合以侏罗系烃源岩为主力烃源岩,具有良好的资源潜力。     

The Late Triassic Callide Coal Measures, Queensland, Australia: Coal petrology and depositional environment

The Late Triassic (Carnian-Rhaetian) Callide Coal Measures are preserved in a partly fault-bounded basin remnant in east-central Queensland, Australia. The sequence comprises up to 150 m of interbedded clastic sedimentary rocks and at least four major coal seams, including one coal body up to 23 m thick. The sequence was deposited initially in high-gradient alluvial fan systems which gave way through time to sandy, low-sinuosity rivers. The restricted, intermontane and entirely alluvial nature of sediment accumulation is here considered to have influence the petrographic characteristics of Callide coals, and their external geometry.The main coal seam from the Callide Measures shows variation in the predominance of some macerals, indicating successions of environmental changes. The application of transmission electron microscopy (TEM) to the study of the Callide coal has enabled a better understanding of the nature and origin of some of the less understood macerals such as micrinite and vitrinite B. Two forms of vitrinite have been observed, each with a distinct reflectance range. The wood-sourced vitrinite A displays an average reflectance of 0.56%, implying a higher rank than the 0.49% Ro total vitrinite reflectance recorded in previous publications. Vitrinite B and A together represent the most commonly occurring macerals in the Callide coal samples of the present study. The lower-reflecting vitrinite B which forms bands, often several hundred μm in thickness, in TEM shows sub-micron electron transparent laminae of lipid-rich material alternating with a more conventional vitrinite material. The vitrinite B is interpreted to represent accumulations of leaves.The Callide coal has entered the oil window, and oil has been generated from some exinite, cutinite, and resinite, as evident from change in fluorescence and the presence of exsudatinite in cell cavities and cleats. Vitrinite B is seen under the microscope to also be generating oil. Micrinite, the origin of which has been much debated, occurs in selected horizons only, as lenticular bodies suggesting cell filling or filling of spaces between laminations in vitrinite B. TEM shows micrinite to consist predominantly of sub-micron pyrite and possibly other mineral particles adsorbed on humic acids.     

吐哈盆地煤成烃主要贡献组分剖析

吐哈盆地中下侏罗统煤显微组分组成显示了“碎、小、薄”和过渡组分含量高的特点。结合显微和超微层次有机岩石学分析，在显微组分层次生烃组分主要为基质镜质体，碎屑类脂体、薄壁角质体、木栓质体和小孢子体在煤成烃中也有一定的贡献；超微层次生烃组分主要表现为分布于基质镜质体中的超微类脂体。煤中基质镜质体的高含量弥补了其单位生烃潜力低的不足，基质镜质体富氢成因在于生物化学阶段细菌等微生物对其强烈降解改造作用。     

The optical features and hydrocarbon-generating model of “barkinite” from Late Permian coals in South China

Leping coal is known for its high content of “barkinite”, which is a unique liptinite maceral apparently found only in the Late Permian coals of South China. “Barkinite” has previously identified as suberinite, but on the basis of further investigations, most coal petrologists conclude that “barkinite” is not suberinite, but a distinct maceral. The term “barkinite” was introduced by (State Bureau of Technical Supervision of the People's Republic of China, 1991, GB 12937-91 (in Chinese)), but it has not been recognized by ICCP and has not been accepted internationally.In this paper, elemental analyses (EA), pyrolysis-gas chromatography, Rock-Eval pyrolysis and optical techniques were used to study the optical features and the hydrocarbon-generating model of “barkinite”. The results show that “barkinite” with imbricate structure usually occurs in single or multiple layers or in a circular form, and no definite border exists between the cell walls and fillings, but there exist clear aperture among the cells.“Barkinite” is characterized by fluorescing in relatively high rank coals. At low maturity of 0.60–0.80%R_o, “barkinite” shows strong bright orange–yellow fluorescence, and the fluorescent colors of different cells are inhomogeneous in one sample. As vitrinite reflectance increases up to 0.90%R_o, “barkinite” also displays strong yellow or yellow–brown fluorescence; and most of “barkinite” lose fluorescence at the maturity of 1.20–1.30%R_o. However, most of suberinite types lose fluorescence at a vitrinite reflectance of 0.50% Ro, or at the stage of high volatile C bituminous coal. In particular, the cell walls of “barkinite” usually show red color, whereas the cell fillings show yellow color under transmitted light. This character is contrary to suberinite.“Barkinite” is also characterized by late generation of large amounts of liquid oil, which is different from the early generation of large amounts of liquid hydrocarbon. In addition, “barkinite” with high hydrocarbon generation potential, high elemental hydrogen, and low carbon content. The pyrolysis products of “barkinite” are dominated by aliphatic compounds, followed by low molecular-weight aromatic compounds (benzene, toluene, xylene and naphthalene), and a few isoprenoids. The pyrolysis hydrocarbons of “barkinite” are mostly composed of light oil (C₆–C₁₄) and wet gas (C₂–C₅), and that heavy oil (C₁₅⁺) and methane (C₁) are the minor hydrocarbon.In addition, suberinite is defined only as suberinized cell walls—it does not include the cell fillings, and the cell lumens were empty or filled by corpocollinites, which do not show any fluorescence. Whereas, “barkinite” not only includes the cell walls, but also includes the cell fillings, and the cell fillings show bright yellow fluorescence.Since the optical features and the hydrocarbon-generating model of “barkinite” are quite different from suberinite. We suggest that “barkinite” is a new type of maceral.     

Geological and laboratory evidence for early generation of large amounts of liquid hydrocarbons from suberinite and subereous components

Suberinite, and subereous components of amorphous nature, comprise largely unrecognized, proficient sources of liquid hydrocarbons. Due to difficulties in recognizing the presence of subereous components and suberinite in organic sediments, the contributions of these liptinitic components to the organic input of source rocks are easily underestimated. Severe chemical alterations of suberinite in the vitrinite reflectance range of R_o = 0.35–0.60% are demonstrated. Organic geochemical data, obtained from samples subjected to natural maturation, reveal that subereous components/suberinite undergoes early thermal degradation to generate large amounts of hydrocarbons below R_o = 0.60%. Data obtained from laboratory maturation of immature, suberinite-rich coals indicate that about 50% of the potential of suberinite for generating C₁₂₊ hydrocarbons has already been exhausted during natural maturation of the samples, prior to the onset of the traditionally defined “oil window”. The present data (a) contradict the assumption that suberinite is mainly sourced by selective preservation/enrichment of a stable, highly aliphatic biopolymer, i.e. “suberan” and (b) suggest that suberinite contains appreciable amounts of aliphatic and aromatic moieties which are released at low thermal stress.     

煤成烃生成及排驱加水热模拟实验

用加水热模拟实验对采于我国胜利油田附近的石炭系太原组亮褐煤（R0＝0．56%）生烃潜力进行研究。煤样富含镜质组（74．5%）,壳质组少（8．8%）,惰性组占16．7%,其中镜质组以富氢的基质镜质体为主。煤样裂隙发育,形成于滨海沼泽相沉积环境。实验设200℃、230℃、260℃、290℃、320℃和350℃六个温度点,每个温度点加热72小时。实验结果表明该煤具有较高的生烃潜力和排油效率。其液态烃大量生成和排出始于R0＝0．76%（290℃）,在R0＝1．18%（320℃）时达高峰。气态产物从R0＝1．18%大量形成,直到R0＝1．53%（350℃）继续增大。实验分析认为煤的生烃能力除了与其有机质类型、有机质丰度等有关外,还与其形成的沉积环境有关,缺氧的还原环境是煤作为烃源岩形成和保存的有利沉积环境。裂隙的发育有助于煤成油的排驱和运移。     

地质条件下湖相烃源岩生排烃效率与模式

烃源岩排烃研究是油气地球化学研究中最薄弱的环节,而排烃效率又是准确评价常规油气与非常规页岩油气资源的关键参数。目前对于烃源岩排烃效率的认识差异很大,尚未建立完整的各种类型有机质湖相烃源岩在地质条件下生排烃效率与模式。本文以中国渤海湾、松辽等4个大型湖相含油气盆地以及酒泉青西凹陷、泌阳凹陷等9个中小型湖相富油盆地/断陷为对象,通过15000余个湖相烃源岩样品在自然热演化过程中热解生烃潜力指数的变化研究,揭示了湖相烃源岩在地质条件下的生排烃特征,构建了湖相烃源岩在地质条件下的生排烃效率与模型。无论是大型湖相沉积盆地还是中小型断陷盆地,甚至是盐湖相沉积盆地,烃源岩生排烃特征基本一致。随着成熟度的增高,湖相烃源岩排烃效率逐渐增高,在低成熟阶段排烃效率较低,在成熟与高成熟阶段具有高或很高的排烃效率。Ⅰ型、Ⅱ型有机质类型烃源岩排烃模式相似,相对排烃效率在低成熟阶段小于45%,成熟生油高峰时达85%~90%,至生油窗下限时达90%以上;累积排烃效率在低成熟阶段小于10%,生油高峰时达50%~60%,生油窗下限时达75%~85%,主要的排烃阶段在镜质组反射率0.7%~1.2%之间,生油窗阶段生成并排出了绝大部分烃类。湖相Ⅲ型有机质烃源岩排烃效率明显低于Ⅰ、Ⅱ型有机质烃源岩,生油窗阶段累积排烃效率仅为50%左右,主要生排烃阶段在镜质组反射率0.8%~2.0%之间。控制湖相烃源岩排烃量和排烃效率的主要因素是有机质丰度、类型和成熟度,而盆地类型、断裂发育程度、烃源岩沉积环境、相邻输导层孔渗条件等因素均不影响烃源岩排烃与排烃效率。     

煤成油生成和运移的模拟实验研究 Ⅲ．甾、萜标记物特征及其意义

在对两个褐煤样品进行同时考虑生烃和排烃模拟实验的基础上，本文对其甾、萜标记物的组成、分布和演化进行了研究，探讨了其生源意义、成熟演化及与自然演化的异同和甾、萜参数作为运移指标的意义。     

新疆侏罗纪煤中木栓质体的特征和演化

对吐鲁番-哈密等盆地100多块煤样有机岩石学分析表明:新疆早中侏罗世煤中普遍含有木栓质体.木栓质体在煤有机显微组分中所占比例仅以木栓化细胞壁计.一般在2%以下,若包括木栓化细胞壁和充填在胞腔中的团块镜质体两部分则最高可达20%.在镜质体反射率0.35%~0.70%时,木栓质体光性发生明显变化,但其形态和数量没有显著变化,反映了木栓化细胞壁中木栓质和蜡质在低成熟阶段明显失去,而作为细胞壁格架的纤维素、木质化纤维素则没有显著变化.随热成熟作用木栓质体光性逐渐向结构镜质体和均质镜质体演化;至镜质体反射率0.90%时二者已难以分辨.      

The Statistical Prediction of the Vitrinite Reflectance and Study of the Ancient Geothermal Field in Songliao Basin,China

The resource of the gas from coal and coal measures deep in Songliao Basin hasbeen drawing more and more attention to.It is necessary to find out the evolution regulari-ty of the geothermal field of the basin in addition to a series of geological studies in orderto predict its resources because the ancient geothermal field of the basin is one of themain factors controlling the generation,evolution and disappearance of oil and gas.Inthe recent twenty years,it is generally believed that vitrinite reflectance is the best quanti-tative marker for the ancient geothermal field.In the present paper,a systematic studyof the vitrinite reflectance value of Songliao Basin and its influence factors is made by mul-tiple statistical analysis so as to reconstruct the evolutional process of the Moho and thecorresponding geothermal field.Then,an overall prediction is made of the vitrinitereflectance and the distribution of J_3-K_1 fault basin group at the bottom of SongliaoBasin,which provides the evidence for the furth     

南方下古生界海相页岩有机质成熟度评价

为明确适用于南方下古生界海相页岩成熟度评价的沥青反射率与镜质体反射率等效换算关系,利用初始成熟度接近的洪水庄组海相页岩及龙潭组煤样在350~525℃温度范围开展了系列共置热压模拟实验,通过测定各温度下页岩中的沥青与煤中的镜质体反射率的演化规律,建立了两者之间的等效换算关系,并利用模拟样品和实际剖面样品开展了方法验证.结果表明两者满足以下关系:VR_o（等效镜质体反射率）=0.879 8R_b（沥青反射率）+0.114 5（适用范围:VR_o 0.61%~3.04%）,本次建立的沥青反射率回归公式可以为准确评价缺乏镜质体的高演化海相页岩地层的成熟度判定提供重要参考.      

新疆西北部和什托洛盖盆地侏罗系低熟煤系烃源岩地球化学特征及生烃条件分析

新疆西北部和什托洛盖盆地勘探程度较低,侏罗系煤系烃源岩较为发育,选取了和什托洛盖盆地和布克河凹陷与白杨河凹陷的四条侏罗系野外地质剖面,对侏罗系烃源岩进行了系统的地球化学实验室分析测试,确定了该盆地生烃潜力。研究表明,侏罗系八道湾组、三工河组以及西山窑组煤系烃源岩有机碳含量、氯仿沥青“A”、总烃以及生烃潜力值均达到中等—好的烃源岩有机质丰度标准。煤系烃源岩有机质显微组分镜质体较为富集,壳质组相对含量达到20%,为孢子体、角质体、树脂体以及木栓质体,泥岩富集部分藻类体,荧光特征较强,惰质体不发育,母质类型为Ⅱ2型,部分为Ⅲ型,煤为Ⅲ型,煤中氯仿沥青“A”与族组分同位素偏重,暗色泥岩略低,煤系烃源岩族组分非烃的同位素值均明显偏轻,芳烃同位素略重,受控于煤系烃源岩中多环芳烃较为发育,更为富集δ13C,非烃组分N、S、O化合物富集δ12C。实测Ro值较低,烃源岩成熟度偏低,但盆地模拟结果表明研究区凹陷中心区源岩已进入生烃门限。研究区低熟煤系烃源岩分子标志化合物也存在其特殊性,正构烷烃以高碳数的分布为主,煤的Pr/Ph值明显高于泥岩,无β 胡萝卜烷、孕甾烷与升孕甾烷分布、伽玛蜡烷指数低,表明侏罗系煤以湖沼相的氧化环境为主,而西山窑组泥岩主要以弱氧化环境沉积特征为主,另外萜烷系列化合物几乎无倍半萜、二环倍半萜以及三环萜烷的分布,藿烷系列存在ββ生物构型分布,为热演化程度较低的标志,分子标志化合物参数的相关性表明,弱氧化的湖沼相的沉积水体有利于此类化合物的分布,煤抽提物中规则甾烷C27、C28、C29呈反“L”型分布,主要以高等植物的陆源输入为主,而侏罗系泥岩存在“V”型分布,有低等水生藻类的贡献,与富氢组分中存在藻类体有较好的的匹配关系,具有更有利的生烃条件。     

Characteristics of hydrocarbon generation from organic macerals in Jurassic coal measures, Xinjiang, China

The Jurassic coals of the Junggar and Turpan-Hami basins, Xinjiang, China, are characterized by abundant vitrinite. Microscopic analysis of Junggar coal samples indicates that they contain desmocollinite and hydrogen-rich vitrinite with a low reflectivity. The hydrocarbon-generating potential of various macerais follows the decreasing order of exinite > vitrinite > inertinite. However, desmocollinite is a principal maceral for hydrocarbon generation in this area because the content of vitrinite is higher than that of exinite. Data from simulating experiments and infrared spectra show that the hydrocarbon-generating process occurred primarily at the lower-mature stage in the Middle-Lower Jurassic coal measures. Generally, crude oil from the Qigu oilfield has a close similarity in hopanoid distribution to the vitrinite and exinite from the Jurassic strata with C₂₃-C₃₂ pentacyclic triterpanes and γ-lupane being present. The distribution of steranes is also similar. C₂₉-sitostane is dominant and Q₂₇ ergostane is subordinate. Only a trace amount of cholestane is present. All this suggests that the crude oil from the Qigu oilfield was derived from Jurassic coal measures.